CN1223377A - Cellulose binding domain - Google Patents

Abstract

A cellulose binding domain (CBD) having a high affinity for crystalline cellulose and chitin is disclosed, along with methods for the molecular cloning and recombinant production thereof. Fusion products comprising the CBD and a second protein are likewise described. A wide range of applications are contemplated for both the CBD and the fusion products, including drug delivery, affinity separations, and diagnostic techniques.

Description

Cellulose binding domains

The present application is a divisional application of an invention patent application having application number 941924408, filed on 14/4/1994 and entitled "cellulose binding domain".

This application is a continuation-in-part of U.S. patent application serial No.08/048,164 filed on 14.4.1993.

The present invention relates to a Cellulose Binding Domain (CBD) that binds cellulose and chitin in a significantly high affinity and reversible manner to non-water soluble forms, including crystalline forms of cellulose and chitin. The CBD of the present invention has been isolated. The CBD of the invention is substantially free of other proteins with which it is naturally associated and has been found useful for the biological immobilisation of a wide variety of substances, particularly biologically active molecules, to cellulose. Also disclosed are fusion products comprising a CBD and a second protein of interest, including the use of formulations thereof in a variety of methods. These fusion proteins have a variety of beneficial applications including applications in isolation, purification, and diagnostic methods.

Immobilization of chemical substances including biologically active proteins is important in industrial production. Various immobilization methods have been developed in recent years. However, most of these methods require modification of the immobilization matrix. In general, these modifications require covalent binding of the ligand to the matrix, which in many cases leads to loss of ligand activity, and doping with certain toxic organic compounds that must be removed beforehand for subsequent use of the matrix in pharmaceutical or food processing. A typical example of a widely used product is protein A-Sepharose. This very expensive product allows for affinity chromatography purification of IgG and for diagnostic methods.

The use of chimeric proteins containing functional regions (catalytic or other functions) together with binding regions is a relatively new technology, but has proven to be particularly useful as a protein purification method. For example, a glutathione S-transferase gene fusion system is designed to express a useful gene fused to the C-terminus of glutathione S-transferase. The recombinant protein was purified by affinity chromatography using a glutathione-Sepharose column.

Another example of a chimeric protein having functional and binding domains is the protein A gene fusion vector, which can be used to express fusion proteins at high levels in E.coli and S.aureus cells (B. Nilsson, et al (1985) EMBO J.4(4): 1075-1080.) the IgG binding domain of protein A provides a rapid purification of fusion proteins using IgG-Sepharose columns A similar system based on β -galactosidase fusion proteins purified on IPTG-Sepharose or metal chelate chromatography columns or histidine hexamer proteins purified using Ni-resin columns has been developed.

Cellulose is well suited for immobilizing an enzyme used in the treatment of wine and fruit juices, i.e., endo- β -glycosidase (Shaseyov et al, J.Agric.food chem.38: 1387-.

Cellulose, which can bind certain ligands without resorting to chemical modifications (i.e., "bio-immobilized"), should have certain advantages, particularly in that the resulting solid phase matrix is natural and non-toxic (without "dirty chemical modifications"). Other advantages may include the resulting solid phase matrix retaining its physical properties, as well as its relatively low price. At present, the price of cellulose is 500 times lower than that of glutathione-Sepharose and IPTG-Sepharose, so that cellulose becomes an attractive and low-cost matrix material which can be safely used in the food and pharmaceutical industries. Recently, Greenwood et al (FEBS Lett.224(1):127-131(1989)) fused the cellulose binding domain of the enzyme Cellulomonas fimi endoglycosidase to alkaline phosphatase. The recombinant fusion protein retains its phosphatase activity and ability to bind to cellulose (see also U.S. Pat. No.5,137,819 to Kilburn et al).

Unfortunately, however, the cellulose binding domain of Monospora coprostana (Cellulomonas fimi) exhibits only a relatively low affinity for cellulose. For example, more than 30% of the fusion protein is washed away with 50mM Tris-HCl (pH7.5) in 0.5M NaCl. A second disadvantage of the cellulose-binding domain of fecal fibromonas (C.fimi) is that the cellulose fibers are destroyed after binding to the C.fimi-binding domain (Din et al, Bio/Technology 9: 1096-. Thus, even though the c.fimi cellulose binding domain may not exhibit direct cellulase activity, this destructive effect on the cellulose substrate fiber (which is equivalent to a physical change in the morphology of the solid phase matrix) is likewise problematic and undesirable (see discussion in section 7.3, below).

Many cellulases and other hydrolases, such as chitinases, have high affinity for their substrates (Shoseyov, et al, PNAS, USA 87:2192-2195 (1990); cab, Methods Enzymol,161, pp.460-462 (1988)). It has previously been shown that strong binding between crystalline cellulose and cellulase is directly related to the ability of cellulase to degrade crystalline cellulose (Klyosov, Biochemistry 29: 10577-.

Shoseyov et al (PNAS, USA 87: 2192-. The cellulase "complex" exhibits cellulase activity on crystalline cellulose and carboxymethylcellulose and is a large protein complex composed of several different polypeptides. It has been found that in order for the catalytic enzyme to break down crystalline cellulose, a large (about 200kD) major cellulose binding protein (CbpA) with no significant enzymatic activity must be involved with the catalytic enzyme. However, it is not necessary to have such CbpA involved in order to enzymatically degrade amorphous cellulose. Shoseyov et al (PNAS, USA89: 3483-3487(1992)) reported the cloning and DNA sequencing of the CbpA gene, where 4 separate "putative" cellulose binding regions within CbpA were also described.

Heat Shock Proteins (HSPs) are inducible in prokaryotic and eukaryotic organisms under various stress conditions. Based on their molecular weight, HSPs are divided into several families of homologous proteins.

The 60kD HSP (HSP 60) family, which retains unusually high levels of sequence conservation during evolution, is the focus of interest for use as potential antigens in autoimmune diseases (W.Van Eden (1991) immunol. Rev.121: 1; W.Van Eden, Thole R.Van der Zee, A.Noordzij, J.D.A.Van Einbden, E.J.Hensen and I.R.Cohen (1988) Nature 331: 171; M.B.J.Billingham S.Carney, R.Bulter, and M.J.Colston (1990) J.Exp.Med.171: 339).

There is experimental evidence that the response to hsp60 must be controlled by regulatory T cells. There is evidence to suggest that T cell reactivity is at least partially directed against mammalian endogenous HSPs (b.herman et al, (1991) eur.j.immunol.21: 2139).

The hsp60 protein family from many different organisms, including Mycobacterium tuberculosis (Mycobacterium tuberculosis), Mycobacterium barbadosnut (Microbacterium leprae), Mycobacterium bovis (Mycobacterium boyyi BCG), Escherichia coli (E.coli), Chinese hamster and human cells, has been cloned and sequenced (V.Mera et al, (1986) PNAS, USA 83: 7013; S.J. et al, (1989) mol.cell biol.9: 2279; O.J.Pickerts et al, (1989) J.biol.Chem.264: 12001; T.M.nnick (1987) J.biol.169: 1080; T.M.Shinnick et al, (1988) Infect.56: 446; T.Ver.J.J.R.1990) Pte.9: Pte.9. coli.18. and 1990).

As described below, Heat Shock Proteins (HSPs) or portions thereof, anti-HSP antibodies or portions thereof can be used in CBD-fusion products according to the invention.

Immune responses to mycobacteria and human hsp60 have been implicated in thedevelopment of autoimmune diabetes in human and animal models.

In addition to immunodominant antigens, the hsp60 family of proteins has been shown to perform a "chaperone" role in the proper folding of protein complexes in a variety of systems, the presence of newly synthesized polypeptide chains and, in many cases, their assembly. (S.M.Memmingsen et al., Nature 333:330: R.J.Ellis (1990) Sem, Cell biol.,1: 1-9).

In the mouse insulin-dependent diabetes mellitus (IDDM) model system-T lymphocytes reactive to hsp60 antigen were detectable at the onset of insulitis (insulibiis) and it is likely that these T lymphocytes also recognize β cells hsp65 cross-reactive antigen (D.Elias et al, (1990) Proc.Nat Acad.Sci.USA 87: 1576-1580).

Thus, there remains a need for a cellulose binding protein that exhibits a high but reversible affinity for cellulose, particularly crystalline fibers, and which neither exhibits cellulase activity nor destroys fibers of the crystalline fiber substrate (i.e., exhibits the "amorphizing" effect).

The present inventors describe herein the identification of novel Cellulose Binding Domain (CBD) proteins, molecular cloning and their cellulose binding properties. In addition, methods of constructing expression systems for producing fusion products comprising CBB and a second useful protein are disclosed.

The present invention relates to the discovery that CBDs are capable of performing functions independent of other proteins or polypeptides with which they are naturally associated. In addition, CBD has also been unexpectedly found to have a high affinity for crystalline cellulose and chitin with Kd values in the range of about 1.5. mu.M to 0.5. mu.M, preferably about 1.4. mu.M to 0.8. mu.M. Specifically, CBD exhibits Kd values of about 1.2. mu.M or less for various crystalline cellulose samples. An additional feature of CBD is that it is truly devoid of cellulase activity, and it is particularly surprising that CBD does not exhibit morphological alteration characteristics (i.e. no amorphous effects). It was also found that a CBD-fusion product comprising a CBD and a second protein retained the binding capacity of the CBD to cellulose.

The present invention also relates to the discovery that CBD can bind cellulose unrestrictedly over a wide pH range and under various buffer conditions, that a significant amount of CBD binds to crystalline cellulose, and that CBD is not released from cellulose upon exposure to water. In clear contrast, the major CbpA protein and the binding domain from c.fimi are readily dissociated from cellulose after exposure to water. To release the CBD from the cellulose it is necessary to contact it with a denaturing solution such as 6M guanidine hydrochloride, 6M urea or a non-ionic surfactant. Thus, the function and behavior of the CBD protein is completely independent of other proteins with which it is naturally associated in its binding to cellulose.

Thus, the present invention provides an isolated CBD protein capable of binding cellulose with high affinity and being substantially free of other proteins with which it is naturally associated.

In one embodiment of the invention, the CBD protein comprises the amino acid sequence shown in figure 1. In another embodiment of the invention, the CBD protein comprises an amino acid sequence which is at least 70% homologous, preferably 80% homologous to the amino acid sequence disclosed in FIG. 1. In another embodiment of the present invention, it is desirable that the nucleotide sequence has at least 60% homology, preferably 70-80% homology with the nucleotide sequence shown in FIG. 1.

In another embodiment of the invention, the CBD has a high affinity for cellulose. The CBD of the present invention preferably hasa Kd value of about 1.5. mu.M or less, and most preferably has a Kd value of about 1.0. mu.M or less.

In another embodiment, the invention provides a CBD fusion protein comprising a CBD protein capable of binding cellulose with high affinity and a second protein, wherein when said CBD protein is a naturally occurring protein, said CBD protein is substantially free of other proteins with which it is naturally associated. In a particular embodiment of the invention, the second protein is protein a. In another embodiment of the invention, the second protein is an HSP protein. In yet another embodiment of the invention, the second protein fused to the CBD may consist of two or more polypeptide regions. For example, a CBD may be associated with a variable light chain (V) of an antibody or functional part thereof_L) And variable heavy chain (V)_H) And (4) fusing.

Another embodiment of the invention provides a method of producing a CBD or CBD fusion product. One method that can be applied to a CBD alone or a CBD fusion product, but is recited herein for a CBD fusion product, can include the following steps: providing a nucleic acid encoding a CBD fusion product, wherein said CBD fusion product comprises a CBD and a second protein, said CBD being capable of binding cellulose or chitin with high affinity and being substantially free of other proteins with which it is naturally associated; transforming a host cell with the nucleic acid or introducing the nucleic acid into a host cell using equivalent means; and culturing the transformed host cell under conditions suitable for expression of the CBD fusion protein. In the above method, the second protein may further comprise an N-terminal amino acid and a C-terminal amino acid. Host cells can be transformed by a variety of methods well known to those skilled in the art, including but not limited to electroporation, injection, calcium chloride precipitation, and retroviral introduction. Furthermore, the nucleic acid may be integrated or not integrated with the genome of the host cell.

In another aspect of the invention, a method of purifying a CBD fusion product is provided, comprising contacting a mixture comprising a recombinant CBD fusion product with an effective amount of cellulose under conditions suitable for the formation of an insoluble binding complex comprising cellulose and the recombinant fusion product; separating the insoluble cellulose-CBD fusion product binding complex from the mixture; and recovering the CBD fusion protein from the cellulose-CBD fusion product binding complex.

In a particular embodiment of the invention, the method of purifying a CBD fusion protein of the invention further comprises providing a nucleic acid encoding a cleavage site located upstream of the N-terminal amino acid of the second protein of the CBD fusion product.

In another embodiment of the invention, the method of purifying a CBD fusion protein further comprises providing a nucleic acid encoding a cleavage site downstream of the C-terminal amino acid of a second protein of the CBD fusion protein.

In yet another embodiment of the invention, the method of purifying a CBD fusion protein of the invention further comprises providing a nucleic acid encoding a second protein of the CBD fusion protein upstream of the first cleavage site for the N-terminal amino acid and downstream of the second cleavage site for the C-terminal amino acid of the second protein.

Likewise, the mixture comprising the CBD is contacted with an effective amount of cellulose to purify the CBD. The resulting insoluble CBD cellulose binding complex is separated and then treated with a release agent to yield a purified CBD.

Another aspect of the invention is to provide an isolated nucleic acid encoding a CBD protein capable ofbinding cellulose with high affinity and substantially free of other nucleic acids with which it is naturally associated. An isolated nucleic acid encoding a protein of the invention can be used as a probe for screening a cDNA or genomic library for sequences having homology to the cbd gene.

In another embodiment, the invention provides a host cell comprising a nucleic acid encoding a CBD of the invention.

Another aspect of the invention relates to a diagnostic kit for detecting a substance of interest, comprising: (a) the CBD fusion product comprises (i) a CBD capable of binding cellulose with high affinity and being substantially free of other proteins with which it is naturally associated, and (ii) a second protein capable of binding to the substance of interest; (b) a detectable label; and (c) cellulose. Chitin may be used in place of cellulose in such a kit. In particular embodiments of the invention, the second protein of the CBD fusion product may be a protein A, HSP protein, an HSP antibody, an HSP-related protein, a peptide, or an antigenic portion thereof. The term "peptide" includes molecules consisting of 2-20 amino acids. The CBD fusion product in the diagnostic kit described above may further comprise a ligand that binds with affinity to the second protein, the ligand being capable of binding to the substance of interest. "ligand" refers to any molecule capable of binding to a second molecule by non-covalent means. For example, primary IgG can affinity bind to protein a fused to CBD. The IgG can then be used as a ligand for a particular protein, peptide, or hormone.

In another aspect of the invention, an immunoassay for detecting the presence of a substance of interest is disclosed, the method comprising: (a) incubating a test sample which may contain a substance of interest with a sufficient amount of a CBD fusion product comprising (i) a CBD which is capable of binding cellulose with high affinity and is substantially free of other proteins with which it is naturally associated, and (ii) a second protein which is capable of binding the substance of interest under conditions which allow the substance of interest to bind to the second protein in the CBD fusion product; (b) adding an amount of cellulose effective to bind to the specific amount of CBD fusion product used in step (a) to obtain an insoluble cellulose-CBD fusion product binding complex; (c) separating the insoluble cellulose-CBD fusion product binding complex from the unbound components; (d) incubating the insoluble cellulose-CBD fusion product binding complex with a sufficient amount of a detectable label, wherein said label is capable of binding to the substance of interest to be detected; and (e) separating the insoluble cellulose-CBD fusion product binding complex of step (d) from the unbound components and detecting the presence of the detectable label to identify the presence of the test substance of interest in the test sample.

Also disclosed is another method for detecting a substance to be detected in a test sample, which comprises: (a) contacting a test sample, which may contain a substance to be tested, with an insoluble matrix capable of immobilizing the substance to be tested; (b) incubating the insoluble matrix with a sufficient amount of a CBD fusion product, wherein said fusion product comprises (i) a CBD capable of binding cellulose with high affinity and substantially free of other proteins with which it is naturally associated, and (ii) a second protein capable of binding the immobilized test substance under conditions that allow the immobilized test substance to bind to the second protein of the CBD fusion product; (c) separating the insoluble matrix of step (b) from the unbound components; (d) incubating the insoluble matrix of step (c) with a detectable label capable of binding to the substance of interest or the CBD fusion product under conditions that allow binding of the label to the substance of interest or the CBD fusion product; and (e) separating the insoluble matrix of step (d) from the unbound components and detecting the presence of the label to provide an indication of the presence of the test substance of interest in the test sample.

The method may further comprise (i) contacting the insoluble matrix of step (c) with a sufficient amount of cellulose under conditions which allow the cellulose to bind to the CBD fusion product to form a cellulose-CBD fusion product binding complex, and (ii) separating the insoluble matrix of step (i) from unbound components including unbound cellulose. The method may employ a label capable of binding the substance of interest or the cellulose-CBD fusion protein binding complex, particularly cellulose in the cellulose-CBD fusion protein binding complex. The test sample may be a bodily fluid including, but not limited to, blood, urine, semen, saliva, mucus, tears, vaginal secretions, and the like. Chitin can often be used instead of cellulose. Alternatively, the insoluble matrix may be an electrophoretic gel blot.

In a particular embodiment of the invention, a method for detecting a protein or peptide is devised; thus, the second protein of the CBD fusion product may be an antibody against the protein or peptide. The antibody may be a monoclonal antibody or a polyclonal antibody. Alternatively, the CBD of the invention may be attached to the antibody of interest either directly or via a linker moiety.

The test substance of interest may also include biotinylated probes bound to proteins, peptides, hormones, nucleic acids, or other molecules that can be used as probes for targets. In this case, the preferred second protein is streptavidin. When the label comprises an enzyme, the method further comprises adding a sufficient amount of an enzyme substrate, wherein said substrate is converted by the enzyme to adetectable compound.

Detection may be performed in a competitive manner. Thus, the above method can be modified such that step (d) is accomplished by incubating an insoluble cellulose-CBD fusion product binding complex with a sufficient amount of a detectable label comprising a labeled substance of interest, wherein the label is capable of binding to any second protein in the CBD fusion product that is not bound to the substance of interest; and step (e) is accomplished by separating the insoluble cellulose-CBD fusion product binding complex of step (d) from unbound components and comparing the signal measured from the test sample with the signal measured from the control sample.

In a preferred embodiment of the invention, the CBD fusion product is included in a dip stick (dip stick). Accordingly, it is also an object of the present invention to provide a dip stick for detecting a substance of interest in a test sample comprising a CBD fusion product, wherein the CBD fusion product comprises (i) a CBD capable of binding cellulose with high affinity and being substantially free of other proteins with which it is naturally associated, and (ii) a second protein capable of binding the substance of interest. The second protein is preferably selected from the group consisting of a protein A, HSP protein, an HSP antibody, a cross-reactive HSP-related protein or peptide or antigenic portion thereof, an enzyme, a hormone, an antigen and an antibody.

Also, an object of the present invention is to provide a signal amplification system comprising: (a) a first CBD fusion product comprising (i) a CBD capable of binding with high affinity to cellulose and being substantially free of other proteins with which it is naturally associated, and (ii) a second protein capable of binding to a chimeric probe which further binds to a substance of interest; and (b) a second CBD fusion product comprising (i) a CBD capable of binding cellulose with high affinity and being substantially free of other proteins with which it is naturally associated, and (ii) an enzyme capable of acting on a substrate to produce a detectable compound.

In another embodiment, a signal amplification system is provided comprising the following components: (a) a CBD fusion product comprising (i) a CBD capable of binding with high affinity to cellulose and being substantially free of other proteins with which it is naturally associated, and (ii) a second protein capable of binding to a chimeric probe which further binds to a substance of interest; and (b) a labeled CBD that retains its ability to bind cellulose with high affinity and is substantially free of other proteins with which it is naturally associated.

These signal amplification systems may comprise chimeric probes and may also comprise a cellulose matrix, preferably a gravel-milled cellulose.

These signal amplification systems may include systems designed to identify nucleic acids in cells or tissues, and systems designed to extend the length of the identified nucleic acids in each direction using oligonucleotide-directed thermal cycling DNA amplification methods that delete sequences, wherein DNA-specific primers may be used in combination with a degenerate, vector-specific, or oligo-dT-conjugated second oligonucleotide to direct specific sequence synthesis.

Finally, it is a further object of the present invention to provide a drug delivery system comprising a CBD that binds to a drug, wherein the CBD retains its ability to bind to cellulose with high affinity and is substantially free of other proteins with which it is naturally associated. In such a drug delivery system, the drug is attached to the CBD either directly or through a linker moiety. There are many methods of attachment and are known in the art. For example, an acyl activator such as a conventional cycloheximide can be used to form an amide or ester linkage. Thus, drugs having nucleophilic groups such as amino or hydroxyl groups can be attached to the carboxyl terminus of the CBD. In one embodiment, such a drug delivery system may be a slow or sustained drug delivery system, wherein the drug of interest is slowly released from the CBD bound to the cellulose.

In one embodiment, the drug to be released is an antifungal agent. Preferred agents include, but are not limited to, amphotericin B, nystatin, and undecylenic acid. The drug may typically be an imidazole, such as Clotrimazole. It may be desirable to incorporate such a drug delivery system into a composition that can be administered parenterally, orally, topically or by inhalation. In particular, routes of administration include, but are not limited to, intranasal, intraocular, or intravaginal administration. In addition, the formulation may be a solid, gel, liquid or aerosol.

The drug delivery systems described herein are suitable for delivering drugs against infections or pathogenic agents, such as yeast or fungi that contain cellulosic or chitin material in their cell membranes, including but not limited to members of the genera Aspergillus fumigatus, Candida or Monilia, or epidermal cells. With the drug delivery system of the present invention, it is expected that the dosage required to effectively treat a disease or infection will be greatly reduced, thereby improving the efficacy of the use of these antifungal or antifungal drugs, which are also generally quite toxic. It is desirable to minimize or eliminate side effects of the drug.

Another aspect of the invention relates to the ability of CBD to alter plant tissue growth. This capability is applicable in agriculture, for example, and is expected to promote pollen tube growth and/or root growth. In addition, because of their ability to inhibit root growth, high concentrations ofCBD can be used to prevent the development of undesirable plants, such as "weed" plants. In another embodiment, the CBD is applied to promote the growth of fungi such as mushrooms, wherein the CBD binds to chitin and stimulates the growth and/or development of developing basidiocarp or fruiting bodies.

Yet another aspect of the invention relates to the ability of CBDs to bind to insect exoskeletons and chitin from other insect sites, including the midgut. This ability of the CBD is suitable for its use as a biological pesticide, where the CBD is linked to a microorganism for controlling pests, such as Bacillus Thuringiensis (BT) or other microorganisms expressing the BT toxin gene, or a chitinase-secreting microorganism or fungus. CBD binds microorganisms to the chitin portion of insects, where toxins or enzymes produced by the microorganisms cause the pests to die. Microorganisms exhibiting chitinase activity include bacterial strains of the genera Enterobacter and Streptomyces, as well as fungal strains of the genera Aspergillus, Penicillium, and Trichoderma. In one form of this embodiment of the invention, the CBD-microorganism complex may be applied directly to the parts of the plant suspected of being infected or at risk of being infected by the pest, or alternatively the CBD-microorganism complex may be immobilised on bait stations located in infected fields or on plants infested with pests. In another form of this embodiment of the invention, the CBD-microorganism complex is applied to forest trees or cellulose-containing products to prevent or control infection by wood-destroying pests. For example, CBD-microorganism complexes are applied to telephone poles and wood or cellulose-containing building elements, where the CBD component binds tightly to invading insects, and the microorganisms in the complex are effective in controlling pests.

Yet another aspect of the invention relates to the ability of CBDs to bind to chitin in fungi, including fungi suitable for bioremediation or degradation of toxic environmental pollutants. According to one form of this embodiment, a CBD fusion protein is used in which the second component is an enzyme that degrades environmental pollutants. The CBD-enzyme fusion protein may be immobilized on a cellulosic substrate and the tool used to remove environmental contaminants via enzymatic degradation, for example, the tool may be placed in a stream of surface or groundwater. Most according to another alternative embodiment of this embodiment of the invention, the CBD is bound to a fungus capable of producing bioremediation enzymes, i.e. enzymes secreted by the fungus degrade environmental pollutants such as pesticides. The CBD-fungal complex is then immobilized on a cellulosic substrate and provides a tool suitable for enzymatic degradation of environmental contaminants such as pesticides including DDT, or wood-containing products left over from logging or sawing operations. In an illustrative embodiment, the CBD is complexed with a white spoilage fungus, such as, for example, chrysosporium fulvum, to produce lignin peroxidase, manganese peroxidase and to degrade the pesticide DDT. The CBD-fungus complex is suitable for bioremediation, such as the removal of pesticides like DDT from the environment.

FIGS. 1A-1B: the nucleotide (upper, original strand; second, complementary strand) and the deduced amino acid sequence of the CBD.

FIGS. 2A-2C: preparation and cloning of a fragment of the gene encoding CBD.

Analysis of the hierarchical structure of CbpA, which contains an N-terminal signal peptide, a unique CBD region, 4 hydrophilic repeats (white arrows) and 9 hydrophobic repeats (black arrows).

PCR primers arranged along the CbpA gene. The primer sequences for the CBD flanking region and the CbpA DNA sequence are included for clarity. The PCR product contained Nco I and BamH I sites (underlined). It is also noted that the ATG start codon of the gene fragment is located within the NcoI site and the TAG stop codon is adjacent to the BamHI site.

C. pET-CBD containing CBD gene fragments cloned into pET-8c vectors are illustrated. The vector contains the necessary transcriptional and translational signals for inducible CBD production.

FIG. 3 expression and purification of CBD protein

The lanes in the figure show the whole cell protein of the pET-8 c-carrying cells loaded on a 15% acrylamide gel (lane 2), the whole cell protein of the pET-CBD-carrying cells (lane 3), the cytoplasmic fraction of the lysed pET-CBD cells (lane 4), the guanidinium hydrochloride-solubilized membrane/inclusion body fraction of the lysed pET-CBD cells (lane 5), Avicel^_The final PC buffer eluate of the pellet (lane 6), and the purified CBD protein (lane 7). The lane is as followsA fraction of 0.005% of the total protein was loaded, but lane 6 used a 10-fold higher protein concentration. The prestained molecular weight standards (lanes 1,8) had mobilities of approximately 2.6, 5, 12.7, 18.1, 29 and 44 kDa.

FIG. 4 CBD-Avicel^_Time course of binding. Balance CBD (2.0. mu. mol total protein) and Avicel as described in section 7 below^_(1mg/ml) except that a larger total volume was used to provide samples taken at different time points. Samples were washed at each time point and tested as described in section 7. See also table i below or fig. 9.

FIG. 5 GBD and Avicel^_Combined double reciprocal plots. Black squares represent 0.5mg Avicel^_(B) Black circle represents 1mg Avicel^_(J) The black triangle represents 2mg (H). Insertion diagram: PCmax vs. Avicel used^_The amount of (c). The detection value was 1.0 ml.

FIG. 6 CBD and Avicel^_Bound Scatchard plots. FIG. 3 shows different amounts of Avicel^_Time [ PC]]/[P]Plots were made for PC. [ PC]]/[P]Dimensionless scale of expression, [ PC]Expressed in units of μ M. Black circle represents 1mgAvicel^_Empty circle represents 2mg Avjcel^_The black squares represent 3 mg.

FIG. 7 CBD binding to Cellulon^_Double reciprocal diagram of (1). The incubation mixture contained 0.5mg Cellulon per ml^_。

FIG. 8 CBD-protein A fusion protein binds to cellulose and IgG. 1M acetic acid selectively releases CBD-protein A IgG "linkages", but not CBD-protein A: cellulose is "bonded".

FIG. 9 adsorption of CBD proteins on water-insoluble substrates.

FIG. 10 overexpression and purification of CBD.

FIG. 11: a signal amplification system is illustrated in which labeled CBD-detects cellulose or chitin bound to CBD fusion products. The substance of interest is bound, which in turn binds to the chimeric probe.

FIG. 12: the scheme shows that where the substance of interest binds to the ternary CBD fusion product: signal amplification system on CBD-protein a (igg).

FIG. 13: IgG was purified with CBD-protein a-cellulose as demonstrated by examining the samples according to gel electrophoresis. Lane a is human serum. Lane b is human serum protein which does not bind to CBD-protein A-cellulose. Lane c is the first PBS eluate of the sample showing unbound protein after IgG has bound to protein a. Lane d is the IgG fraction recovered by washing with acetic acid.

Fig. 14A and 14B: it was demonstrated that the CBD treated cellulose fibers remained intact, i.e., the CBD was not active in breaking the amorphous state. Fig. 14A shows cotton fibers treated with CBD. Fig. 14B shows untreated cottonfibers (control).

FIG. 15: the effect of pH and NaCl concentration on the ability of CBD-protein A to bind cellulose was demonstrated.

FIG. 16: binding of CBD to A.niger was demonstrated. Lane a is A.niger with CBD added. Lane b is A.niger without CBD (control). Lane c is a mono-CBD.

FIG. 17: binding of CBD to Spodoptera Littoralis was demonstrated. Lane a is the midgut membrane of Spodoptera Littoralis without CBD (control). Lane b is the midgut membrane of Spodoptera Littoralis with CBD added.

FIG. 18: binding of CBD to Heliotbis armigera was demonstrated. Lane a is the midgut membrane of Heliothis armigera without CBD (control). Lane b is the midgut membrane of Heliothis armigera supplemented with CBD.

FIG. 19: the effect of CBD and BSA (as controls) on pollen tube growth was demonstrated.

FIG. 20: demonstration of the effect of CB) on the cell wall composition of pollen tubes stained with a white fluorescent brightener (calcofluor). FIG. 20A shows that CBD treated pollen tube produced an amorphous pollen tube tip as indicated by the absence of a bright color on the tip zone band. FIG. 20B shows that the tip of the control pollen tube contains more crystalline cell wall components as indicated by the bright color.

Fig. 21A and 21B: gold immunolabeling of CBD-treated pollen tubes was demonstrated. FIG. 21A demonstrates that in pollen treated with CBD, the gold marker is along the pollen tube but preferably appears in the apical zone as indicated by the strong dark spot on the apical zone. Fig. 21B shows control, i.e. pollen without CBD treatment.

FIG. 22: the effect of CBD on root growth of Arabidopsis thaliana (Arabidopsis thaliana) seedlings was demonstrated. Different letters indicate statistically significant differences (p.ltoreq.0.05) between root length values.

FIG. 23: gold immunolabeling of CBD-treated Arabidopsis thaliana (Arabidopsis thaliana) seedlings was demonstrated. The figure shows that the gold mark is limited to the root and the stem does not show a mark.

FIG. 24: staining of Arabidopsis seedlings (Arabi dopsis thaliana) with a white fluorescent brightener (calcofluor) was demonstrated. The figure demonstrates that only the roots are stained, indicating that they are accessible to cellulose.

The present invention relates to the identification of Cellulose Binding Domain (CBD) proteins capable of binding to cellulose with high affinity and in a reversible manner CBDs of the invention are useful, for example, for the biological immobilization of biologically active molecules on cellulose. CBDs of the invention can be fused to a second protein to form a CBD fusion protein where the presence of the CBD protein can be readily and selectively purified by incubation with cellulose. examples of the second protein include protein A, protein G, streptavidin, avidin, Taq polymerase and other polymerases, alkaline phosphatase, ribonuclease (RNase), deoxyribonuclease (DNase), various restriction enzymes, peroxidase, glucanases such as endo-1, 4- β -glucanase, endo-1, 3- β -glucanase, chitosanase, and β and α glucosidase, β and α -glucoronidase, starch translatory enzymes, transferases such as transglycosyltransferases, phosphotransferases, chloramphenicol-acetyltransferase, chloramphenicol-modified acetyltransferase, β -glycosyltransferase, and other proteases, and antibiotic membrane-degrading enzymes, particularly, for the detection of proteins, antigens, proteases, and bacterial membrane-degrading hormones.

Thus, for example, CBD and HSP antigenic factors can be used to test body fluids for the presence of specific antibodies (e.g., Heat Shock Protein (HSP) antibodies). In contrast, CBD-HSP antibody fusion proteins can be used to detect HSP proteins, cross-reactive HSP-related proteins or antigenic proteins thereof.

The term "CBD" or "CBD protein" or "cellulose binding domain protein" refers to a protein comprising the amino acid sequence shown in figure 1, and includes functional homologues and functional derivatives thereof, provided that the functional homologues or functional derivatives have the ability to bind cellulose with high affinity and in a reversible manner. The CBD of the invention is substantially free of other proteins with which it is naturally associated, for example the remainder of the major CbpA protein discussed above. In addition, one or more predetermined amino acid residues in the polypeptide may be substituted, inserted or deleted, for example, to produce a CBD with improved biological properties, or to achieve different binding and expression levels. Certain desired CBD proteins falling within the scope of the present invention may have covalent or non-covalent modifications to the naturally occurring molecules, including but not limited to glycosylation modifications. The CBD protein of the invention having deletions, substitutions and/or insertions of residues may be prepared by altering the nucleic acid encoding it using recombinant DNA techniques. Modifications and mutations that can be made at the DNA level encoding the CBD of the invention do not necessarily alter the reading frame and preferably do not result in complementary regions that will give rise to secondary mRNA structures (see European patent publication No. EP75,444).

The CBD proteins of the invention are at least 70% homologous, preferably 80% homologous, more preferably at least 90% homologous, and most preferably at least 95% homologous to the amino acid sequences shown in FIG. 1. The term "X% homology" is not limited to sequences that are X% homologous over the entire length of the protein. 70% homologyalso includes the X% homology that occurs in the identified functional regions within the CBD protein shown in FIG. 1. Examples of functional regions may be a defined set of amino acids with the ability to bind cellulose in a reversible manner with high affinity. Such protein homologues are also referred to herein as "CBD functional homologues". In one embodiment of the invention, such a functional region may have about 100 amino acids. In another embodiment of the invention, such a functional region may have about 50 amino acids. The most preferred CBD protein of the invention is a protein consisting of the amino acid sequence shown in FIG. 1.

The term "functional derivative of a CBD" as used herein refers to any "fragment", "variability", "analogue", or "chemical derivative" of the amino acid sequence of the CBD protein shown in figure 1, which retains the ability to bind to cellulose in a reversible manner with high affinity, and which is preferably between about 2 and 160 amino acids, more preferably between about 25 and 125 amino acids, and most preferably between about 50 and 100 amino acids in length.

The term "fragment" refers to a CBD protein derived from the CBD protein shown in FIG. 1 and having a naturally occurring sequence. Such fragments may be produced by proteolytic cleavage of the full length protein. Alternatively, the DNA sequence encoding the CBD protein may be suitably modified to produce such fragments recombinantly by deletion of one or more amino acids at one or more sites within the C-terminal, N-terminal, and sequence of the native sequence. The identity or utility of a functional derivative can be determined based on its ability to bind cellulose with high affinity and in a reversible manner to screen fragments of CBD proteins.

The term "variant" as used herein refers to a molecule in which the amino acid sequence, glycosylation pattern, or other characteristic of thenative molecule has been modified, covalently or non-covalently, and is intended to include mutants. Some variants falling within the scope of the present invention have amino acid substitutions, deletions and/or insertions provided that the final construct has the desired ability to bind cellulose in a reversible manner with high affinity. Amino acid substitutions in CBD proteins may be made based on similarity of polarity, charge, solubility, hydrophobicity, hydrophilicity, and/or the amphipathic nature of the residues involved. For example, negatively charged amino acids include aspartic acid and glutamic acid; positively charged amino acids include lysine and arginine; amino acids having uncharged polar center groups or non-polar key groups with similar hydrophilicity values include: leucine, isoleucine, valine; glyconic acid, propionic acid; asparagine, glutamine, serine, threonine; phenylalanine, tyrosine. Also included within the definition of variants are those proteins having additional amino acids at the N-terminus, C-terminus, and at one or more sites within the native CBD sequence, provided that the variants retain the ability to bind cellulose with high affinity and in a reversible manner.

The term "chemical derivative" refers herein to a CBD protein produced by chemically modifying a naturally occurring CBD protein or a variant thereof. Illustrative examples of chemical modifications would be the replacement of H by an alkyl, acyl, or amino group.

The phrase "binds cellulose with high affinity" refers herein to the ability of a CBD protein to bind cellulose with a Kd value in μ M ranging from about 1.5 to 0.5, preferably from about 1.4 to 0.8. More preferably, high affinity binding refers to the ability of the ready-made CBD to bind crystalline cellulose with a Kd value of about 1.1 or less, and most preferably about 1.0 or less.

The phrase "binds cellulose in a reversible manner"refers herein to the ability to release CBD protein from a cellulose-CBD protein binding complex via a releasing agent or solution, such as 6M urea, 6M guanidine hydrochloride, and other denaturing agents, including nonionic surfactants. However, it is preferred to use denaturing agents which allow the released CBD or fusion product to be reconstituted. For example, a denatured protein may be subjected to renaturation conditions as described in sections 6.1.4, 7.1.1, 7.2.1, and 8.1.4 below to reconstitute a CBD from material treated with 6M urea or 6M guanidine hydrochloride.

The term "CBD fusion protein" as used herein refers to the joining together of at least two proteins, a CBD protein and a second protein. In certain embodiments of the invention, examples of the second protein include enzymes, such as nucleic acid modifying enzymes, proteases, hormones or hormone precursors, polypeptides, peptides, antibodies, antigens, epitopes and variants thereof. In certain preferred embodiments of the invention, the second protein is protein a; in other preferred embodiments of the invention, the second protein is an HSP protein. A preferred embodiment of the invention is a fusion protein consisting of a CBD protein, protein A or an anti-HSP recombinant IgG. The CBD fusion proteins of the invention may comprise an enzymatic or chemical cleavage site upstream and preferably adjacent to the N-terminus of the second protein, and/or an enzymatic or chemical cleavage site downstream and preferably adjacent to the C-terminus of the second protein, thereby providing a means for recovering the second protein from the CBD fusion protein using a cleavage reagent.

The term "CBD fusion protein-cellulose binding complex" as used herein refers to a complex formed when cellulose binds to a CBD protein in a CBD fusion protein.

"nucleic acid" refers to a nucleotide sequence, which may be an RNA or DNA sequence, comprising a series of nucleicacids joined in phosphodiester linkages in the 5 'to 3' direction. If the nucleic acid is DNA, the nucleotide sequence is single-stranded or double-stranded. The nucleic acid encoding the CBD protein is RNA or DNA which encodes a CBD protein capable of binding cellulose with high affinity, is complementary to, or hybridizes to, a nucleic acid sequence encoding such a CBD protein and remains stably bound thereto under stringent conditions.

The phrase "nucleic acid encoding a CBD protein of the invention" includes nucleic acids of genomic, cDNA, and synthetic and semisynthetic origin, which are not related to any polynucleotide portion with which it is naturally associated, depending on its source or operation, and may be linked to a polynucleotide other than the polynucleotide to which it is naturally linked, and includes single-or double-stranded polymers of ribonucleotides, deoxyribonucleotides, nucleotidase analogs, or combinations thereof, so long as the encoded CBD retains its ability to bind cellulose with high affinity. The phrase also includes a variety of different modifications known in the art, including but not limited to radioactive and chemical labels, methylation, capping, intranucleotide modifications such as those via charged (e.g., phosphorothioate, phosphorodithioate, etc.) and uncharged (e.g., methyl phosphonate, phosphotriester, phosphoramidate, carbamites, etc.), and modifications containing a docking moiety, an intercalating moiety, a chelator, etc., provided that the CBD encoded by the nucleic acid retains the ability to bind cellulose with high affinity and in a reversible manner.

A nucleic acid encoding a CBD may be used to construct a recombinant expression vector capable of expressing a CBD protein or CBD fusion protein of the invention. A nucleic acid construct is capable of expressing a protein if it contains a nucleotide sequence that includes transcriptional and translational regulatory information and the sequence is "operably linked" to a nucleotide coding sequence. "operably linked" refers to a linkage in which the regulatory DNA sequence and the DNA sequence to be expressed are linked in a manner that permits transcription and ultimately transcription.

In constructing a CBD fusion protein expression vector, the nucleic acid encoding the CBD protein will be linked to the nucleic acid encoding the second protein such that the open reading frame of the CBD protein and the second protein remains intact, allowing translation of the CBD fusion protein. CBD nucleic acids are available from a variety of cellular sources that produce cellulose binding regions that bind cellulose with high affinity and in a reversible manner, or produce CBD-encoding mRNA. A preferred source of CBD-encoding ribozymes is Clostridium cellulovorans (Clostridium cellulovorans). Nucleic acids encoding CBDs may be prepared as described in section 6.1.

The nucleic acid encoding the CBD protein of the invention may be prepared from isolated and purified DNA of cellular origin, or by genomic cloning. Cloned cDNA or genomic libraries may be prepared using techniques known in the art, and a particular CBD-encoding nucleic acid may be screened using nucleotide probes that are substantially complementary to any portion of the gene. If it is desired to detect conserved nucleotide regions encoding CBD proteins, the nucleotide probes should be based on the interspecies conserved CBD nucleotide sequences. If it is desired to detect a unique nucleotide region encoding a CBD protein, the nucleotide probe should be based on a unique CBD nucleotide sequence. Alternatively, cDNA or genomic DNA may be used as a template for PCR cloning with the appropriate oligonucleotide primers. Full-length clones, i.e., clones containing the entire coding region of the desired CBD protein, can be screened for use in constructing expression vectors, or overlapping cDNAs can be ligated together to form the complete coding sequence. Alternatively, the DNA sequence encoding the CBD may be synthesized in whole or in part by chemical synthesis using standard techniques known in the art.

There are many vectors available and the selection of an appropriate vector can be made based on several factors: 1) whether it is used for nucleic acid amplification or nucleic acid expression, 2) the size of the nucleic acid to be inserted into the vector, and 3) to which cell the host cell to be transformed by the vector belongs. Each vector contains different components depending on its function (either the amplified nucleic acid or the expressed nucleic acid) and compatibility with its host cell.

The term "host cell" refers to a cell that is capable of growing in culture and is capable of expressing a CBD protein or CBD fusion protein. Host cells of the invention include cells in vitro culture and include prokaryotic, eukaryotic, and insect cells. Host cell lines may be selected that regulate the expression of the inserted sequences, or modify and process the gene product in the particular manner desired. Expression driven by certain promoters can be increased in certain inducers, such as zinc and cadmium ions for metallothionein promoters. Thus, the expression of the CBD protein or CBD fusion protein can be controlled. The ability to control expression will be important if the CBD protein or CBD fusion protein is lethal to the host cell. Modification and processing of protein products are important for the function of the protein. Different host cells have their characteristic or specific mechanisms for post-translational processing and modification of proteins. An appropriate cell line or host system may be selected to ensure proper modification and processing of the expressed CBD protein or CBD fusion protein. The host cell should secrete minimal amounts of proteolytic enzymes.

In thepresent invention, host cells are provided which contain a nucleic acid encoding a CBD protein or CBD fusion protein of the invention which is capable of binding cellulose with high affinity. Preferred host cells for cloning and expressing the CBD proteins of the invention are prokaryotic cells. Prokaryotic cells are particularly useful for rapidly producing large quantities of nucleic acid, for generating single-stranded nucleic acid templates for site-specific mutagenesis, for simultaneously screening a number of mutants, and for determining the nucleic acid sequence of the mutants produced. An example of a prokaryotic cell for cloning and expression of a CBD protein according to the invention is E.coli XL1-blue strain supplied by Stratagene. Another example of a prokaryotic cell used for cloning and expression of a CBD fusion protein is Staphylococcus aureus. Yet another example of a system for cloning and expressing a CBD protein or CBD fusion protein is the Pichia pastoris (Pichia) expression kit of Invitrogen Corporation (San Diego, Calif.).

For recombinant expression of the CBD protein and the CBD fusion protein, a person skilled in the art can equally well utilize various expression vector/host systems. These systems include, but are not limited to, microorganisms such as bacteria transformed with recombinant phage DNA, plasmid DNA, or cosmid DNA expression vectors containing the desired CBD coding sequences; yeast transformed with a recombinant yeast expression vector comprising the desired CBD coding sequence; insect cell systems infected with recombinant viral expression vectors (e.g., baculovirus) containing the desired CBD coding sequences; plant cell systems infected with a recombinant viral expression vector containing the desired CBD coding sequence (e.g., cauliflower mosaic virus CaMV, tobacco mosaic virus TMV), or transformed with a recombinant plasmid expression vector containing the desired CBD coding sequence (e.g., Ti plasmid); or animal cell systems infectedwith recombinant viral expression systems (e.g., adenovirus, vaccinia virus), including cell lines engineered to contain multiple copies of stably amplified CBD nucleic acid (e.g., CHO/dnfr, CHO/glutamine synthetase) or cell lines containing multiple copies of CBD nucleic acid that are not stably amplified in a two-disc chromosome (e.g., mouse cell lines).

Carrier components generally include, but are not limited to, one or more of the following: a signal sequence, an origin of replication, one or more marker genes, an enhancer element, a promoter, and a transcription termination sequence. The expression elements of these vectors vary in both their length and specificity. Any suitable transcription and translation element may be used, depending on the host/vector system utilized. For example, when cloning in a prokaryotic cell system, a promoter isolated from the genome of a prokaryotic cell (e.g., a bacterial tryptophan promoter) may be used. Promoters produced by recombinant DNA or synthetic techniques may also be used to drive transcription of the inserted sequence.

The signal sequence may be a component of the vector, or may be part of a CBD nucleic acid inserted into the vector. The signal sequence may be a naturally occurring sequence preceding the CBD sequence, or a non-naturally occurring sequence. The signal sequence should be recognized and processed by the host cell. Origin of replication refers to the unique site of origin of replication of the host organism. It is desirable that the cloning and expression vectors contain a selection gene, also referred to as a selectable marker. The gene encodes a protein necessary for the survival or growth of the transformed host cell in a selective medium. Host cells that have not been transformed with a vector containing the selection gene cannot survive in this medium. Typical selection genes encode proteins that confer resistance to antibiotics or other toxins, such as ampicillin resistance, auxotrophic deficiencies in supplementation; or to provide important nutrients not available from complex media. An example of a selection scheme is the use of certain drugs to prevent the growth of host cells. These cells successfully transformed with the heterologous gene can express a protein conferring drug resistance and thus can survive the selection system.

Expression and cloning vectors typically contain a promoter that is recognized by the host organism and is operably linked to a nucleic acid encoding a polypeptide of interest. A promoter is a non-translated sequence (usually in the range of about 100 to 1000 bp) located upstream (5') of the start codon of a structural gene that controls the transcription and translation of a particular nucleic acid sequence operably linked thereto, such as a nucleic acid sequence encoding a CBD protein or CBD fusion protein. Such promoters generally fall into two categories, inducible and structural. Inducible promoters are promoters that initiate increasing levels of transcription of nucleic acids under their control in response to certain changes in culture conditions, such as the presence or absence of a certain nutrient, or a change in temperature. At present, many promoters recognized by a variety of potential host cells are known. Restriction enzymes can be used to remove promoters from the starting nucleic acids and to insert isolated promoter sequences into vectors to operably link these promoters to nucleic acids encoding polypeptides of interest. Naturally occurring promoter sequences and a number of heterologous promoters may be used to direct amplification and/or expression of the polypeptide of interest. However, it is preferred to use heterologous promoters because they generally allow for greater strength of transcription and higher levels of production of the expressed polypeptide of interest than naturally occurring promoters. For these hosts, plasmid vectors containing promoter and control sequences derived from species compatible with the host cell are typically used. The vectors typically carry an origin of replication and a marker sequence capable of providing phenotypic selection in the transformed cells. For example, Escherichia coli is generally transformed using plasmid pBR322 derived from Escherichia coli (Bolivar, et al, Genen 2:95[1977]). The pBR322 plasmid contains ampicillin and tetracycline resistance genes and thus provides an easy tool for identifying transformed cells. The pBR322 plasmid or other microbial plasmid must also contain, or be modified to contain, promoters and other control elements commonly used in recombinant DNA construction.

Promoters suitable for use with prokaryotic hosts include β -lactamase and lactose promoter systems (Chang et al, Nature,275:615 (1978); Goeddel et al, Nature 281:544(1979)), alkaline phosphatase, tryptophan (trp) promoter systems (Goeddel, Nucleic Acids Res,8:4057(1980)), and EPO application No.36,776), as well as hybrid promoters such as the tac promoter (H.de Boere et al, Proc.Natl.Acad.Sci USA 80:21-25(1983), but also other functional bacterial promoters are suitable, their nucleotide sequences are generally known, enabling the skilled artisan to provide any desired restriction sites using linkers or adaptors, operably linking them to Nucleic Acids encoding pro-relaxin (Siebenlist et al, 20: Cell 269) (1980) the promoters used in bacterial systems also contain a pro-relaxin coding Nucleic acid sequence (Dalgar S).

Expression vectors for prokaryotic host cells will also contain sequences necessary for termination of transcription and for stabilization of mRNA. Appropriate vectors containing one or more of the above-described components and including the required coding and control sequences are constructed using conventional ligation techniques. The isolated plasmid or nucleic acid fragment is cleaved, spliced, and religated intothe desired form to produce the desired plasmid.

Particularly useful in the practice of the present invention are expression vectors suitable for expressing nucleic acids encoding CBD proteins in prokaryotic cells. In general, expression involves the use of an expression vector that is capable of efficient replication in a host cell, such that many copies of such expression vector are accumulated in the host cell and the desired polypeptide encoded by the expression vector is synthesized and levels therefrom.

The host cells are transfected and preferably transformed with the above-described expression or cloning vectors of the present invention and cultured in a conventional nutrient medium with the composition appropriately changed for inducing a promoter, transformants are selected, or a gene encoding a desired sequence is amplified.

"transformation" refers to the introduction of a nucleic acid into an organism such that the nucleic acid is replicated as an extrachromosomal element or through chromosomal integration. Unless otherwise indicated, the methods used herein to transform host cells are calcium treatment methods using calcium chloride as described by Cohen, F.N. et al (Proc. Natl. Acad. Sci. (USA)69:2110 (1972)).

In order to confirm the presence of correctly inserted sequences on the plasmids constructed, the ligation mixture was used to transform E.coli K12 strain 294(ATCC 31446) and successfully obtained transformants were selected on the basis of ampicillin or tetracycline resistance. Plasmids from these transformants were prepared, subjected to restriction analysis and/or sequence determination using the Methods described by Messing et al (Nucleic acids ds Res.9:309(1981)) or Maxam et al (Methods in Enzymology 65:499 (1986)).

Host cells can be transformed with the expression vector of the present invention and cultured in a modified conventional nutrient medium suitable for inducing a promoter, and then transformants or amplified genes are selected. Culture conditions of temperature, pH, etc. are previously suitable for the host cell selected for expression and will be apparent to those of ordinary skill in the art.

Prokaryotic cells for producing the polypeptide of the present invention are cultured in an appropriate medium as described in Sambrook et al ((1989) electrophoresis buffers in Molecular Cloning (Nolan, C.ed.), Cold Spring Harbor Laboratory Press, NY, pp.B.23-24; Sambrook et al (1989) Bacterial Media in Molecular Cloning (Nolan, C.ed.) Cold Spring Harbor Laboratory Press, NY, pp.A.1-4).

The choice of host cells producing a CBD protein or CBD fusion protein of the invention can be identified in at least 4 general ways:

(a) DNA-DNA, DNA-RNA or RNA-antisense RNA hybridization: the presence or absence of a nucleic acid encoding a CBD protein of the invention may be detected by nucleic acid hybridization using hybridization probes and/or PCR reaction primers comprising nucleotides homologous to the CBD coding sequence.

(b) Presence or absence of "marker" gene function: host cells carrying a nucleic acid encoding a CBD protein of the invention may be identified and selected based on the presence or absence of certain marker gene functions, such as antibiotic resistance. For example, if the sequence encoding the CBD is inserted into the sequence of a marker gene of a cloning or expression vector, transformants containing the coding sequence can be identified by the loss of function of the marker gene. Alternatively, the marker gene may be placed in tandem with a CBD nucleic acid sequence under the control of the same or a different promoter used to control expression of the CBD coding sequence. Expression of the marker gene in response to induction or selection indicates expression of the sequence encoding the CBD.

(c) By detecting expression of CBD protein or CBD fusion protein mRNA transcripts in the host cells, the transcript levels were estimated: the transcriptional activity of the CBD coding region can be estimated by hybridization assays. For example, polyadenylated RNA can be isolated and analyzed by Northern blotting using probes homologous to the CBD coding sequence or to a specific portion of the same. Alternatively, total nucleic acid from the host cell can be extracted and hybridization to these probes detected; and

(d) the CBD protein or CBD fusion protein is detected by immunoassay or is determined by the ability of the protein to bind cellulose with high affinity and in a reversible aqueous manner. Expression of the CBD protein may be estimated immunologically, for example by Western blotting or immunological detection methods such as the RIA method. Expression of CBD proteins can be estimated from the ability of the expressed protein to bind cellulose with high affinity and in a reversible manner.

The terms "cell" and "cell culture" are used interchangeably and all include progeny and ancestors thereof. It should also be clear that the DNA content of all progeny may not be identical and therefore there may be mutations prepared or occurring by chance. Mutant progeny that have the same function or biological activity are obtained when the cells are screened.

The term "stringent conditions" as used herein refers to hybridization conditions: (1) using low ionic strength and high washing temperatures, for example in 0.015M NaCl/0.0015M sodium citrate/0.1% SDS at 50 ℃; (2) during hybridization using denaturing agents such as formamide, e.g., 50% (v/v) formamide with 0.1% bovine serum albumin/0.1% Ficoll/0.1% polyvinylpyrrolidone/50 mM sodium phosphate buffer (pH6.5) plus 750mM NaCl, 75mM sodium citrate at 42 ℃; or (3) by using50% formamide, 5 XSSC (0.75M NaCl, 0.075M sodium pyrophosphate) 5 XDenhardt's solution, sonicated salmon sperm DNA (50. mu.g/ml), 0.1% SDS and 10% dextran sulfate at 42 ℃ and washing in 0.2 XSSC and 0.1% SDS at 42 ℃.

As used herein, the term "recovering" refers to the ability to release the CBD protein from the cellulose-CBD protein binding complex under conditions which include the use of a releasing agent, such as a denaturing agent such as 6M urea or 6M guanidine hydrochloride. Any releasing agent that has the ability to release the CBD protein from the cellulose-CBD protein binding complex may be used. The CBD is preferably temporarily denatured and not irreversibly degraded by treatment with a release agent. Thus, CBD can be recovered by reconstituting the eluted protein as described in sections 7.1.1, 7.2.1, and 8.1.4.

The term "cleaving agent" as used herein refers to a substance that specifically cleaves a CBD protein or CBD fusion protein to provide release or cleavage of certain components as desired. A second protein, such as a CBD fusion protein. Suitable cleavage agents include enzymes such as endoproteases, prohormone convertases, e.g. PC1, PC2, furin (furin) Kex2, subtilisins, or mutants thereof; and chemical agents such as organic and inorganic acids, hydroxylamine, N-bromosuccinimide and cyanogen bromide. The following documents teach methods for the enzymatic hydrolysis of peptide bonds using various proteolytic enzymes: the Enzymes,3rd Edition, Boyer, Ed., Academic Press, Vol. III (1971); enzymology, Vol. XI X, Perlman and Lorand, Ed., New York, Academic Press (1970); meth.enzymol., Vol.XL V, Lorand, Ed., New York: Academic Press (1976); drapeau, J.biol.chem.,253: 5899-. A more extensive list of chemical cleavage agents is available in the literature, see Witcop, Advances in Protein Chemistry, Anfinsen et al, ed.,16:221-321, Academic Press, New York (1961), including Table III on page 226 thereof. Othercleavage agents suitable for use in the present invention will be apparent to those skilled in the art and may be selected depending on the cleavage requirements and whether the agent is capable of acting as a reduced or oxidized CBD fusion protein. The conditions used to cleave the CBD fusion protein will depend on the cleaving agent used, and one skilled in the art can determine the cleavage conditions depending on the cleaving agent used.

The CBD fusion proteins of the invention are designed and constructed to include codons necessary to accomplish cleavage with the desired cleavage agent at the desired location (i.e., upstream, preferably at the N-terminus of the second protein in the adjacent CBD fusion protein; or downstream, preferably at the C-terminus of the adjacent second protein; or at both adjacent termini when the second protein in the fusion protein is an internal amino acid of the fusion protein).

The term "glycosylation" and grammatical derivations as used herein refers to the process of post-translational modification by adding a series of sugar residues to a protein to produce a glycoprotein. Glycosylation can occur in the mammalian cytoplasm, endoplasmic reticulum, or golgi apparatus. Alternatively, glycosylation can be accomplished synthetically, for example by providing an appropriate glycosyl donor (see, e.g., Kahne et al, J.am.chem.Soc.,111:6881-2 (1989)).

The invention also relates to diagnostic assays for proteins of interest in test samples, particularly biological samples such as tissue extracts, or body fluids such as serum or urine, using the CBD fusion proteins of the invention. The biological sample is preferably of mammalian origin, and most preferably of human origin. Preferred proteins of interest in a mammalian biological sample to be detected are HSP proteins, HSP antibodies, cross-reactive HSP-related proteins, or antigenic portions thereof. Thepresence of HSP antibodies in a biological sample from a mammal may be predictive or indicative of Insulin Dependent Diabetes Mellitus (IDDM). In one embodiment of the invention, a CBD-protein a fusion protein comprising a third protein, e.g., an IgG antibody against HSP, is used to detect the presence of an antigen, e.g., HSP, in a biological sample, e.g., by various immunoassays known in the art. Alternatively, antibodies recognizing an epitope can be detected using a second protein that is a CBD fusion protein comprising the epitope. Preferred epitopes are HSP proteins.

Protein a is a protein found in the cell wall of staphylococcus aureus that binds to the Fc portion of IgG molecules and thus precipitates antibodies. Proteins have utility in immunoassays, such as RIA or ELISA, which can be used to isolate antibodies or antigen-antibody complexes.

In the present invention, protein a is a preferred second protein of the CBD fusion protein. The CBD-protein a fusion protein can be used in diagnostic immunoassays to detect the presence of, or determine the amount or concentration of, antibodies or antibody-antigen complexes.

The CBD-protein A fusion proteins of the invention may also be used in diagnostic kits comprising cellulose and a CBD fusion protein, wherein the CBD fusion protein component retains its ability to bind to IgG, e.g. an antigen-antibody complex or an antibody, of the cellulose and the second component. The CBD fusion proteins of the invention may also be used as a tool for affinity purification of antibodies or epitopes. Preferred epitopes of the invention are HSP proteins, related proteins or antigenic portions thereof. Preferred second proteins of the CBD fusion protein include HSP proteins or anti-HSP IgG. In the present invention, the CBD-HSP epitope fusion protein can be used in an immunoassay for quantitatively detecting HSP antibodies in human serum.

In another embodiment of the invention, the CBD fusion protein comprises a CBD component that retains its ability to bind cellulose or chitin, and a second component that is an enzyme that retains its catalytic activity. The CBD fusion proteins of this embodiment may be used as a tool for performing enzyme-catalyzed reactions on cellulose or chitin solid phase substrates. As described above, the purified CBD may be linked to a pure enzyme preparation by conventional chemical methods, or the nucleic acids encoding the CBD and the enzyme may be expressed recombinantly to produce a CBD-enzyme fusion protein. In one example of this embodiment of the invention, the second component of the CBD fusion protein is heparinase (heparanase). CBD-heparinase may be immobilized on a cellulose substrate and catalyses the conversion of heparin into sugar components.

Another aspect of the invention relates to the ability of the CBD to alter the growth of plant tissue based on the ability to be suitable for use in agriculture, such as might be expected to promote pollen tube growth and/or root growth. In addition, because of the ability of high concentrations of CBD to inhibit root growth, it can be used to prevent the growth of undesirable plants, such as "weeds". In another example, CBD may be used to enhance the growth of fungi such as mushrooms, where CBD binds chitin and stimulates the growth and/or development of developing basidiomycetes or fruiting bodies.

Yet another aspect of the invention relates to the ability of CBDs to bind to chitin on insect exoskeletons or other insect parts including the midgut. This capability is suitable for the use of CBD as a biological pesticide, where the CBD is linked to a microorganism for controlling pests, such as Bacillus Thuringiensis (BT) or a microorganism expressing the BT toxin gene, or to a fungus that secretes chitinase. The function of the CBD is to bind the microorganism tothe chitin portion of the insect, where the toxins or enzymes produced by the microorganism cause death of the pest. In one example of this embodiment of the invention, the CBD-microorganism complex may be applied directly to a plant part that may be infested or at risk of infestation by pests, or the CBD-microorganism complex may be immobilised at a bait station located in an infested field, or on a plant infested by pests. In another example of this embodiment of the invention, the CBD-microbial complex is applied to wood or cellulose-based products to prevent or control infestation by wood-destroying pests. For example, a CBD-microorganism complex is applied to telephone poles or wood or cellulose-containing building members, wherein the CBD component is tightly bound to invading insects, and the microorganisms in the complex are effective for controlling pests.

Yet another aspect of the invention relates to the ability of the CBD to bind to fungi, including chitin, which are suitable for bioremediation or degradation of toxic environmental pollutants. According to one example of this embodiment, a CBD fusion protein is used in which the second component is an enzyme that degrades environmental pollutants. The CBD-enzyme fusion protein may be immobilized on a cellulosic substrate and the tool used to remove environmental contaminants via enzymatic degradation, for example, the tool may be placed in a stream of surface or groundwater. According to another alternative embodiment of this embodiment of the invention, the CBD is bound to a fungus that secretes enzymes for bioremediation, i.e. degradation of environmental pollutants such as pesticides. The CBD-fungal complex is then immobilized on a cellulosic substrate and provides a means suitable for enzymatic degradation of environmental contaminants (such as pesticides including DDT, or wood-containing products remaining from logging or sawing operations). In an illustrative embodiment, the CBD is complexed with a white spoilagefungus, such as Phanerochaete chrysosporium, to produce lignin peroxidase, manganese peroxidase and degrade the pesticide DDT. The CBD-fungus complex is suitable for bioremediation, such as the removal of pesticides like DDT from the environment.

The term "antibody" as used herein includes polyclonal antibodies, monoclonal antibodies (MAbs), humanized or chimeric antibodies, single chain antibodies, anti-idiotypic (anti-Id) antibodies, as well as epitope-binding fragments of such antibodies. An epitope refers to an antigenic determinant of an antigenic molecule.

The term "IgG" refers to a class of antibodies. IgG is a tetramer containing two light chains and two heavy chains representing 80% of all immunoglobulins.

The term "detectable label" as used herein refers to any label that directly or indirectly provides a detectable signal and includes enzymes, radiolabeled molecules, fluoresceins, particles, chemiluminescent agents, enzyme substrates or cofactors, enzyme inhibitors, magnetic particles. Enzymes useful as detectable labels in the present invention include alkaline phosphatase and horseradish peroxidase. The detectable label can be attached to the protein of interest in a variety of ways, for example, an enzyme such as horseradish peroxidase can be attached to the protein of interest using a bifunctional reagent such as 4,4 '-difluoro-3, 3' -dinitro-diphenyl sulfone. The linked enzyme is then reacted with a substrate to produce a detectable reaction product.

Also included within the scope of the invention are signal amplification methods wherein a detectable label consisting of a CBD protein is used that allows the detection of nanomicrgram quantities of the substance of interest. In the method, a first CBD protein that is part of a CBD fusion product is incubated with cellulose fibers under conditions suitable for the formation of a cellulose-CBD fusion product binding complex. Excess labeled CBD, e.g., CBD fused or bound to an enzyme such as horseradish peroxidase or alkaline phosphatase or fluorescein or a chemical dye, is incubated with the cellulose-CBD fusion product binding complex under conditions suitable for binding of excess labeled CBD. Efficient binding of excess labeled CBD to the cellulose-CBD fusion product binding complex allows detection of very low amounts of the substance of interest. In the signal amplification method of the present invention, the preferred cellulose fiber is a pebble-milled cellulose fiber. The pebbled, milled cellulose fibers may be stained with various chemical dyes or mixed with a fluorescent whitening agent, calcofluor, whereby the cellulose is bound and produces a strong bright blue fluorescence upon irradiation with ultraviolet light.

Also included within the scope of the invention is a solid phase Polymerase Chain Reaction (PCR) wherein a first CBD protein that is part of a CBD fusion product is incubated with cellulose fiber under conditions suitable for forming or cellulose-CBD fusion product binding complexes, and wherein a thermocycling amplification reaction occurs on the binding complexes.

It is also within the scope of the present invention to use a streptavidin/biotin detection system. Biotin is capable of forming a tight, substantially irreversible complex with streptavidin. In this aspect of the invention, a CBD fusion product comprising a CBD protein fused to a superior streptavidin is provided. The nucleotides or proteins are biotinylated using techniques known to those skilled in the art to form biotinylated chimeric probes capable of binding to the substance of interest. The biotinylated probe is incubated with the substance of interest, CBD-streptavidin is incubated with the biotinylated probe, and the biotinylated probe is detected with a detectable label and the substance of interest is subsequently detected. The detectable label may be a label as described above in the signal amplification method, or any other label such as fluorescein or a chemical dye.

Also included within the scope of the invention are therapeutic or diagnostic applications of the CBD fusion products, wherein the CBD fusion subject is a monoclonal antibody. For example, a CBD fusion product comprising (i) a CBD capable of binding cellulose with high affinity and substantially free of other proteins with which it is naturally associated, and (ii) a monoclonal antibody capable of binding antigen, may be used in a method of targeting a drug/cellulose complex or an imaging agent/cellulose complex directed against a cancer cell producing the antigen. In this embodiment, the CBD-monoclonal antibody (or an equivalent antibody fragment, scFv fragment or antigen-binding region thereof) fusion product is administered to a mammal. Simultaneously or after the CBD fusion product is applied, a drug/cellulose or imaging agent/cellulose complex is applied. The binding of the drug/cellulose or imaging agent/cellulose complex to the CBD fusion product is localized at the site of the antigen target, and the drug or imaging agent exerts the desired therapeutic or diagnostic activity at the relevant site.

Example (b): experiments to clone the putative cellulose binding region

Bacterial strains and plasmids

All cloning experiments used the blue strain of E.coli Xl1 from StrateGene (La Jolla, Calif.). Studier et al (J.mol.biol.,189:113-130(1986)) describe E.coli BL21(DE3) and pET-8 c.

Material

PC buffer, pH7, containing 50mM KH₂PO₄、10mM Na₃3C₅H₅O₇(sodium citrate) and 1mM NaN₃. The TEDG buffer (Chang et al, J.Bacteriol.172:3257-3263(1990)) contained 10mM Tris, pH7,0.1mM EDTA,0.1mM dithiothreitol, and 5% (v/v) glycerol. Although Tris has a low buffering capacity at pH7, this buffer is suitable because neither hydrogen ions are produced nor used. Restriction endonucleases all other chemicals used were obtained from BRL (Bethesda, Md.) as commercial reagents of highest purity. Crystalline fibre Avicel^_PH101 (batch #1117) was obtained from FMC corporation (Philadelphia, Pa.). Cotton degreased was obtained from Seamless Rubber Co. (New Haven CT). Cellulon^_Fibers are supplied by Weyerhaeuser (Tacoma, WA). Granular chitin from crab shells was purchased from Sigma. All other binding substrates were purchased from Sigma chemical Co (st. louis, MO). Each polysaccharide was washed twice with PC buffer before use. Removing Aspergillus niger polysaccharide and Cellulon^_And cotton, the quality of polysaccharides all refer to their dry weight as supplied by the manufacturer. All three of these binding substrates have large particle sizes that interfere with detection. The solid of aspergillus niger polysaccharide was dissolved in hot water, filtered and cooled on ice to obtain the recrystallized. Milling with Gifford-Wood for 5 min to reduce Cellulon^_And the size of the cotton fibers.

Cloning of putative cellulose binding regions

A DNA primer complementary to the region of cbpA flanked by the putative CBD (cbpA residues 28-189) (Shoseyov et al, PNAS, USA89: 2482-3487(1992)) was synthesized using Gene Assembler Plus (Pharmacia). The forward primer contained the Nco I recognition site (recognition sequence: CCATGG) in which there was ATG in reading frame with the gene fragment, to serve as a transcription initiation codon when the gene was cloned into the pET-8c vector cloning site. The reverse primer contains a stop codon and a BamHI site. Using 20pmol each of the primers, 200. mu.M dNTP and 1ng of cbpA DNA as a template [ cloned into thevector pGEMEX-1(Promega) (Shoseyov et al, 1992, supra)], a Polymerase Chain Reaction (PCR) was performed in a total volume of 100. mu.l. Wherein Taq polymerase was purchased from Amersham and buffer conditions recommended by the manufacturer were used. PCR was performed for 40 cycles under the conditions described (Innis et al, Optimization of RCRs, PCR Protocols Ed. Innis et al, pub. academic Press, San Diego, pp.3-12 (1990)). The PCR product was purified by extraction with phenol/chloroform, followed by settling with ethanol and washing with 70% ethanol, followed by vacuum drying and resuspension in 27. mu.l of distilled water. The DNA was then cleaved with Nco I and BamH I and electrophoresed on a 2.5% low melting point agarose (Nuseive GTG, FMC) gel in TBE buffer (Sambrook et al, (1989) Electrophoresis buffers in Molecular Cloning (Nolan, C.ed.), Cold Spring Harbor Laboratory Press, NY, pp.B.23-24). The DNA bands stained with ethidium bromide were visualized under long-wave UV light and excised from the gel. The vector plasmid pET-8c was prepared by cleaving 1. mu.g of pET-8c DNA with Nco I/BamH I and cutting a linearized DNA band from the gel. The vector and insert DNA were ligated together using the Takara ligation kit with 100ng vector DNA and 300ng insert. Competent E.coli Xll-Blue strain was transformed with the ligated plasmid and then plated on L B plates containing 100. mu.g/ml ampicillin and 12.5. mu.g/ml tetracycline (Sambrook et al, (1989) Bacterial Media in Molecular Cloning (Nolan, C.ed.), Cold Spring Harbor Laboratory Press, NY, pp.A.1-4). After overnight incubation at 37 ℃, colonies were collected and cultured in liquid LB medium containing ampicillin and tetracycline. Plasmid DNA was obtained from each culture as described (Sambrook et al, (1989), Molecular Cloning (Nolan, C.ed.), Cold Spring Harbor Laboratory Press, NY) and cleaved with restriction enzymes to confirm insertion of the gene fragment. The sequence of the insert was further confirmed by DNA sequence analysis using the method reported by Shoseyor et al (1992) PNAS, USA89: 3483-87).

Expression of CBD

The over-expression vector (pET-CBD) allowed us to overproduce the 17kDa CBD in E.coli strain BL21(DE 3). CBD accumulates in inclusion bodies up to at least 70 mg/l. However, additional amounts of water-soluble CBD of about 20 mg/liter can be recovered from the water-soluble sonic extract of E.coli. Mixing the clarified extract with (Sigmacell 20) cellulose; the CBD-cellulose complex was then washed with 1M NaCl solution and distilled water to remove non-specific proteins, and then pure CBD was eluted with 6M guanidine hydrochloride. The CBD was fully renatured and its ability to bind to cellulose was restored by slow dialysis at room temperature. (FIG. 10, lane 2)

Example (b): purification of CBD proteins

Preparation of CBD proteins

Purification of CBD proteins

Coli BL21(DE3) was transformed with plasmid DNA containing the insert. Plasmid-containing cultures were shake-cultured at 37 ℃ in NZCYM (Sambrook et al, (1989), Molecular Cloning (Nolan, C.ed.) Cold spring harbor Laboratory Press, NY) medium containing ampicillin (100. mu.g/ml) to Klett reading 160 (green filter). At this point IPTG was added to a final concentration of 1 mM. After 4 hours, the cells were harvested by centrifugation, resuspended in 50mM phosphate/12 mM citrate pH7(PC) buffer containing RNAse A (10. mu.g/ml) and DNAse I (1. mu.g/ml), and sonicated on ice with a Biosonic II sonicator at maximum power for 45 seconds; the cells were lysed by cooling for another 15 seconds, and this treatment was repeated 4 times. The insoluble fraction of 1 liter of cell culture was collected by centrifugation (4 ℃,12,000g,30 min) and resuspended in 20ml of 6M guanidine hydrochloride. The suspension was placed on ice for 30 minutes with intermittent agitation to separate the pellet mass. Insoluble debris was removed by centrifugation (4 ℃,12,000g,30 min) and the soluble guanidine hydrochloride extract was gradually diluted to a total volume of 400ml with tegg renaturation buffer over a 2 hour period at 4 ℃. Ammonium sulfate was added to 80% saturation. After standing at 4 ℃ for 4 hours, the precipitated protein was collected by centrifugation (4 ℃,12,000g,30 minutes), resuspended in 40ml of PC buffer, and dialyzed against PC buffer.

The CBD protein fragment of cbpA was further purified by affinity chromatography on a cellulose column: 1.0g Avicel was added three times^_PH101 microcrystalline cellulose removes CBD protein from the solution. After each addition the suspension was allowed to equilibrate (slow rotation at room temperature for 1 hour). The cellulose is then collected by centrifugation and removed before the next additionThen, the operation is finished. 3 g of cellulose were washed 1 time with 1M NaCl/PC buffer and 2 times with PC buffer. The purified CBD was eluted from the cellulose 3 times by washing with 10ml 6M urea. The urea eluted fractions were combined and dialyzed against PC buffer (4 ℃ to room temperature). The protein concentration in the final purified fractions was analyzed colorimetrically using a Micro BCA protein assay kit (Pierce, Rockford, IL) with Bovine Serum Albumin (BSA) as standard.

CBD-cellulose dissociation constant and

detection of cellulose binding Capacity

To a 1.5ml microcentrifuge tube containing PC buffer to which 1mg/ml BSA and the required amount of cellulose (typically 1ml stock solution containing 10mg/ml cellulose and 1mg/ml BSA (in PC buffer)) was added a sample of CBD protein (typically 0 to 100. mu.g). A possible competitor, such as cellulose (4mg/ml) or carboxymethylcellulose (CMC,4mg/ml), was included by adding 200. mu.l of a 20mg/ml stock solution (in PC/BSA buffer). Thefinal volume was always 1 ml. Unless otherwise noted, the pH of the buffer was 7.0. As with experiments conducted at other p H values, the pH of the PC/BSA buffer can be adjusted by the addition of concentrated HCl or NaOH.

The test tube was slowly rotated (30RPM) at 37 ℃ for 1 hour to mix the contents. The samples were then centrifuged in a microcentrifuge for 1 minute to precipitate the cellulose and cellulose-protein complexes. After removal of the buffer, the pellet was washed by resuspending in 1ml of PC buffer. The washings were centrifuged and discarded. The pellet was then resuspended in a final volume of 1ml of PC buffer (since [ C]and [ PC]were concentrated to the same extent, the concentration step was not expected to disturb the equilibrium).

After the washing step, only about 0.1. mu.g of non-specifically adsorbed material remained in the original BSA in the test tube (about 1mg/ml), and 10. mu.l of liquid remained in the pellet. Any color development due to this residual BSA was calculated at 0CBD for the control. Aliquots of the well-mixed suspension were removed and assayed for protein using the Micro BCA kit. According to the instructions provided by the manufacturerThe assay was performed but wherein the sample volume was adjusted to 0.5ml with PC buffer and 0.5ml BCA working reagent was added thereto. The assay mixture was incubated at 60 ℃ for 30 minutes. The protein concentration of the clarified supernatant was detected spectrophotometrically at 562nm in a Shimadzu 160U spectrophotometer. The detection tube, to which no CBD protein was added, was used to correct for the small amount of coloration caused by cellulose and residual BSA. The data obtained were compared to BSA standards and adjusted to a dilution appropriate for determining the amount of protein bound to cellulose in each sample. The practical limit of detection for this assay is about 0.2. mu.g/ml. After calibration of the dilution,this corresponds to about 0.034nmol CBD bound to cellulose in the test tube. From the total CBD concentration [ P]added to the tubes]_tSubtracting the bound protein concentration [ PC]]Calculation of free CBD protein concentration [ P]]： $\[P\]={\[P\]}_c-\[\mathrm{PC}\]---\left(1\right)$ A simple equilibrium relationship (Segel,1975) was assumed to analyze the system: wherein the dissociation constant Kd is defined as: $K_d=\frac{K_{-1}}{K_1}=\frac{\[P\]\[C\]}{\[\mathrm{PC}\]}---\left(3\right)$ equations (4)and W are based on 1/[ PC]at different fixed levels of cellulose]For 1/[ P]]Double reciprocal plot of (d): $\frac{1}{\[\mathrm{PC}\]}=\frac{K_d}{\[\mathrm{PC}{\]}_{\max }}\•\frac{1}{\[P\]}+\frac{1}{{\[\mathrm{PC}\]}_{\max }}---\left(4\right)$ and [ PC]]/[P]To [ PC]]Scatchard plot of (a): $\frac{\[P\]\[C\]}{\[P\]}=\frac{-1}{K_d}\[\mathrm{PC}\]+\frac{{\[\mathrm{PC}\]}_{\max }}{K_d}---\left(5\right)$ these data were analyzed.

It must be noted that cellulose is not a soluble component, and [ C]represents the concentration of binding sites on the cellulose surface per unit volume exposed to the buffer. Similarly, [ PC]represents the concentration of binding site-protein complex per unit volume. The straight line fitting each data point was plotted in a least squares method using deltagraphtprofessional plting application (Deltapoint, inc., Monterey, CA). Each point is the average of three independent protein assay data from the same binding assay tube. Experiments were performed in duplicate. Kd and PCmax/g cellulose were determined using at least two different cellulose amounts. The values were averaged to obtain the values listed in table 1, fig. 9.

Experiments were performed to determine the effect of temperature on CBD binding to cellulose. To 300. mu.l of 50mNPC buffer (pH6), 1M NaCl (final concentration) and 1mg cellulose was added 200. mu.l of CBD (40. mu.g). CBD is/are treated at different temperatures (16 to 60 ℃)Several mixtures of cellulose mixtures were incubated for 1 hour and mixed occasionally, and then centrifuged at 10,000g for 5 minutes. The pellet was washed 2 times with a PC buffer pH6 containing NaCl. Add 40. mu.l of 6M guanidine hydrochloride to the centrifuged pellet, suspend and keep the temperature at room temperature for 30 minAnd (3) minutes. After centrifugation, 20. mu.l of the sample was diluted in 780. mu.l ddH₂Protein concentration was determined in O and using theBio Rad kit.

Detection of binding to other polysaccharides

The detection method uses xylan, Aspergillus niger polysaccharide and Sephadex^_G-75 and chitin to determine if they are binding substrates for CBD proteins. In all cases, the same method of detecting binding to cellulose was used. Chitin exhibited a high background in the MicroBCA assay, where the incubation time was scaled up to 60 ℃ and the color development time was reduced to 15 minutes. Because of the high background of chitin, only two broad different protein concentrations were used.

Purification of CBD for binding assays

To selectively generate the predicted CBD region of cbpA (residues 28-189), oligonucleotide primers complementary to bases 67 to 86 and 558 to 579 of cbpA were designed (FIGS. 1A-1B). As shown in FIGS. 2A-2C, these mismatched primers were designed to create an NcoI site and an ATG start codon at one end of the PCR product and a TAG stop codon at the other end followed by a BamHI site. This gene fragment was then cloned into the T7 RNA polymerase expression vector pET-8c, resulting in the plasmid pET-CBD (see Studier, F., and B.A.Moffatt (1986) J.Mol.biol.189: 113-). The cloned gene fragment encodes the methionine at the N-terminus of the CBD, but the remainder of the CBD amino acid sequence corresponds to residues 28 to 189 of CbpA. The molecular weight of the protein fragment is 17634. DNA sequence analysis confirmed that the insertion had been made. The CBD protein was produced from E.coli EL21(DE3) cells carrying pET-CBD. After addition of IPTG, the host strain produced recognizable T7 in pET vectorT7 RNA polymerase of promoter. CBD gene fragment is under the control of this inducible promoter and after induction a large amount of the CBD protein is incorporated (FIG. 3). After the 4 hour production phase, the soluble extract from the lysed cells contained only asmall amount of CBD protein, while most of the CBD protein was found in the non-soluble fraction. The protein is easily dissolved in the concentrateGuanidine hydrochloride, and can be renatured after slow dilution in tegg buffer. It has been found that proteins isolated in this way can bind to Avicel^_Thus confirming that it is a putative CBD. Although this fraction is essentially all CBD protein, the assay described requires that the protein be of high purity. This purity was achieved by a single cellulose affinity binding purification step using the method described in subsection 7.1.1. When stained with Coomassie Brilliant blue, the affinity purified CBD protein was presented as a single band on an acrylamide gel. Approximately 70mg of CBD protein can be recovered from the cells in 1 liter culture.

Time to CBD binding to cellulose

Effect of Process and temperature on bonding

Avicel^_The time course of interaction with CBD (fig. 4) reveals several features of the process:

(a) at 1.0me/ml Avicel^_And starting concentration of 2.0. mu.M CBD (i.e. [ P]]o), an average value of 1.2. mu.M of the complex was achieved over 60 minutes. Separate experiments confirmed that the maximum CBD binding capacity of the cellulose sample was 2.1. mu. mole × g^-1Equivalent to an effective concentration of 2.1. mu.M total cellulose sites (i.e. [ C]]o). Assuming equilibrium is established (as demonstrated below), then it is defined as [ P]][C]/[PC]Has a Kd of about 0.6. mu.M.

(b) Integral velocity equation (Capellos) by reversible Bi Uni reaction&Bielski, 1980; wilkinson,1980) has a calculated secondary rate constant for binding of approximately 2.7X 10⁴M^-1×min^-1(average of points from 5 to 60 minutes). As K¹Kd calculated rate constant of complex dissociation of 1.6X 10^-2×min^-1(t_1/2=43 minutes). Relatively long dissociated t of complex_1/2Allowing one wash out of C + PCPellet was pelleted without significant loss of bound CBD (resuspension and re-centrifugation of the initial pellet was completed in 1 minute-during which less than 3% of bound CBD would be lost). It was also observed that [ PC]measured after prolonged incubation]Decrease, after 18 hours to a level of about 50% of the maximum.Such [ PC]]The reduction may be caused by gradual denaturation of the protein. To minimize the artefact of base due to these effects, we used a minimum incubation time for which the equilibrium appears to be "complete" (further increase in binding after 60 minutes can be obscured by experimental error). The amount of CBD bound to the cellulose was 4.5+/-0.5 mg/g cellulose and was not affected by temperature over a temperature range of about 16 to 60 ℃.

CBD-cellulose binding affinity

Force and binding Capacity analysis

FIGS. 5A-5B show pure CBD and Avicel^_Typical diagnostic plots for microcrystalline cellulose binding. Within the experimental error norm, the plot is linear, giving a Kd value of about 0.6 μ M per gram of Avicel^_CBD-binding [ PC]max was 2.1. mu. moles. The latter value corresponds to about Avicel per gram^_37mg of CBD protein. The linearity of the diagnostic map suggests that only one type of CBD-cellulose interaction is present.

CBD and Avicel were also investigated^_Other types of cellulose binding ability. Table 1, FIG. 9 shows the values of Kd and PCmax determined for each of the different substrates. Sigmacell20 and 50 are described as microcrystalline forms of cellulose; these materials were also found to bind to CBD. Highly crystalline forms of cellulose such as cotton wool and Cellulon^_The fibers (crystalline cellulose from acetobacter xylinum) were able to bind substantially more CBD (up to 6.4 μmol CBD per gram of substrate). However, fibrous or microparticulate cellulose that has been more processed and therefore contains less cellulose in its native crystalline form has been found to bind a smaller amount of CBD. All forms of cellulose have approximately the same CBD-cellulose dissociation constant, while PCmax values differ by a factor of 30.

Binding site competition

To determine whether soluble carbohydrates were reacted with Avicel^_Competition for binding to the CBD protein, in some assays contained 4-fold (w/v) in Avicel^_An amount of cellobiose (β -1, 4-linked glucose dimer)And CMC (a soluble derivative of cellulose) (1mg Avicel per ml of test sample)^_4mg cellobiose or CMC). As shown in Table 1, FIG. 9, no significant differences in Kd and PCmax were observed, indicating that these soluble carbohydrates did not affect CBD and Avicel^_In combination with (1).

Effect of pH on dissociation constant

Clostridium cellulolyticum (c. cellulovorans) is a neutrophilic organism that only thrives around pH7 (Sleat et al, 1984), so this pH is used in most binding assays. In the pH range of 5.0 to 8.0, PCmax did not change significantly with pH change. In addition, it should be mentioned that PC buffers up to pH3.5 for a partial acid or up to pH9.5 for a partial base do not pass from Avicel during a 1 minute wash^_The CBD was washed off.

Binding of CBD to other polysaccharides

Using xylan, Sephadex^_G-75, Aspergillus niger polysaccharide, and chitin to test the binding specificity of CBD. Of these polysaccharides, only chitin showed detectable CBD peptide binding (table 1, fig. 9). chitin-CBD Kd and binding capacity are similar to Avicel^_CBD binding capacity values.

Our experimental results show that cbpA contains a region that binds cellulose reliably and that this region can function independently of other regions of cbpA. The fact that the purified protein is functional, because of the denaturation and renaturation steps involved in the purification process, indicates that the CBD protein sequence is such that proper folding of the protein fragment is ensured.

We have found that non-specific binding of CBD to test tubes is a problem in conducting equilibrium binding experiments and have established a test for equilibrating CBD with cellulose in the presence of excess BSA. BSA effectively eliminated the nonspecific interaction of CBD with the tube. After equilibration, the cellulose and cellulose-protein complex are collected and washed, and bound protein is detected. As previously mentioned, no detectable amount of CBD was removed in the fast wash step, because the dissociation of CBD-cellulose was slow.

Bound CBD was detected directly by protein detection and the bound CBD was subtracted from the total CBD to calculate the free CBD as shown in 7.1.2, section equation 1. The advantage of this method is that CBD molecules that are non-specifically adsorbed to cellulose with low affinity can be removed by a washing step, thereby obtaining data that more accurately reflects the specific, high affinity interaction between CBD and the cellulose surface. As shown in FIG. 5, data collected using this type of assay constitutes a (within experimental error) linear diagnostic plot. Double reciprocal mapping is a convenient, routine method of determining binding affinity and capacity for the reversible Bi Uni system. The observation that PCmax increases linearly with the amount of cellulose used, while Kd values are independent of the amount of cellulose supports the effectiveness of the assay. Table 1, fig. 9 shows experimental results obtained with various forms of cellulose and other carbohydrates. These results indicate that cellulose described as "crystalline" type has a higher CBD binding capacity than cellulose that has lost most of its crystallinity due to more processing. The fact that PCmax of cellulose samples varies widely depending on the cellulose type, while Kd remains constant indicates that we have detected a type of strong protein-cellulose interaction that occurs between CBD and cellulose. The lower PCmax of highly processed cellulose reflects the presence of a smaller number of potential protein interaction sites in the sample and appears to be related to the crystallinity of the sample. While not wishing to be bound by theory, this result would suggest that crystalline cellulose has certain specific properties that make it acceptable as a binding substrate, whereas non-crystalline cellulose does not.

To further determine the substrate specificity of CBD, we examined the effect of added soluble substrate (cellobiose or CMC) on cellulose binding. As shown in Table 1, FIG. 9, excess cellulose or CMC is on CBD-Avicel^_Kd or PCmax had no effect. This is achieved byA lack of competition suggests that the CBD recognition site is more complex, structure-specific than the simple repetitive glucose or cellobiose moiety, and further suggests that perhapsA specific three-dimensional spatial arrangement of the cellulose chains is required.

The specificity of CBD for crystalline cellulose suggests that chitinase, which is known to bind tightly to chitin, a polymer of acetyl glucosamine linked by β -1,4 bonds, is also classified into a number of different forms, as is cellulose, depending on its source and the purification method used in its isolation (Cabib (1988) Methods enzymol.161: 460. beta. 462: Blackwell (1988) Methods Enzymol,161: 435. 442.) chitin used for affinity purification of chitinase is α -chitin, in which the chains arearranged in an antiparallel manner. this form of chitin is crystalline, which has a structure similar to native crystalline cellulose (commonly known as cellulose I) as opposed to cellulose II, in which the chains are arranged in an antiparallel conformation, cellulose I is in a form in which the cellulose chains are arranged in parallel bundles. processing cellulose under harsh conditions can lead to destruction to produce cellulose II, which is widely associated with the formation of cellulose II, which is found to the two forms of cellulose I.this is also known to be more closely related to the crystalline cellulose-the binding of chitin-CBD- α -A. this form of cellulose-it is also found to be more closely related to the crystalline cellulose-the bonding of chitin-CBD-A. the substrate-CBD- α -the crystalline cellulose-A. this form-it is also found to be more closely related to the crystalline cellulose-the bonding of chitosan-cellulose-the chitosan-A. the crystalline cellulose-A. it is also found to be similar to the crystalline cellulose-A. it is also found that the crystalline cellulose-A. it is similar to the crystalline cellulose-A. it is similar to be similar to the crystalline cellulose-A. it is found that^_G-75(α -1,6 glucose with α -1,3 branches) (Coutinho et al (1992) mol. Microbiol.6:1243-1252), but CBD did not show detectable results with either of them under non-assay conditions.

Although this is intended to be part of the factor favoring tight cellulose binding, recent studies (Din et al (1991) Bio/Teehnol.9: 1096-.

With Aspergillus niger, Spodoptera littoralis

And Heliothis armigera binding CBD

Aspergillus niger mycelia (ca. 20mg) were incubated with 400. mu.l of CBD (120. mu.g) in 20mM Tris-HCl (pH7) for 1 hour at room temperature, the mycelia were washed twice with the same buffer, and the pellet was resuspended in SDS-PAGE loading buffer containing β -mercaptoethanol and SDS, the mixture was boiled for 5 minutes and the proteins were fractionated by SDS-PAGE, FIG. 16 shows that CBD binds to Aspergillus niger mycelia.

The midgut membranes of Spodoptere littoralis and Heliothiargigera (the major insect pathogen in agriculture) were separated under a microscope, approximately 20mg were incubated with 400. mu.l of 20mM Tris-HCl (pH7) containing CBD (120. mu.g) for 1 hour at room temperature, the chitin-containing membranes were washed once with 1M NaCl in the same buffer, then twice with the same buffer without NaCl, and the pellet was resuspended in SDS-PAGE loading buffer containing β -mercaptoethanol and SDS, the mixture was boiled for 4 minutes and the proteins were analyzed by SDS-PAGE, the results are shown in FIGS. 17 and 18.

Construction of CBD-ProtA Gene and its expression in E.coli

Enzymes and chemical reagents

Chemical reagents were purchased from Sigma Chemicals inc. Restriction enzymes were purchased from New England Biolabs Inc. Taq polymerase was purchased from Promega, Inc.

Plasmids and bacteria

Cbd was amplified by PCR using plasmid pCB1(Shoseyov et al, 1992) carrying cbpA. The fusion gene was constructed using the expression vector pRIT2(Nilsson et al (1985) EMBJ.4 (4): 1075-1080). Coli strain XL1-blue (Strategene) was used for the initial transformation. CBD-ProtA was expressed in a strain containing the temperature sensitive repressor, 2097. In addition, E.coli strain N4830-1 carries the temperature-sensitive repressor cj857, which is equivalent to E.coli strain 2097. Coli strain N4830-1 is available from Pharmacia, inc.

Cloning of CBD-ProtA

CBD was amplified by PCR using the cbpA gene as template. Primer a (N-terminal primer;

5 '-GGGGGAATTCCATGGCAGCGACAT-3') contains an EcoRI site, primer B

(C-terminal primer: 5 '-GGGGGGATCCTATGGTGCT-3') containing a termination code

A BamH I site follows. Design and design a new design capable of forcing EcoRI/BamHI 500bp

Cloning of the DNA fragment into a plasmid "in reading frame" fused to the C-terminal part of the protein A Gene

These primers were synthesized in the manner described in pRIT 2. PCR conditions were as described by Innis and Gelfand (1990)

The following changes are made: 2ng of template DNA (cbpa) and

1mM MgCl₂. Using programmable thermal controllers (M)&J Research Inc.)

The reaction is carried out. According to Sambrook et al, in Molecular Cloning (Nolan, C.ed.,

cold Spring Harbor Laboratory Press, NY) by the method described in

Standard DNA manipulations. The PCR amplified product was digested with EcoRI and BamHI and QIAEX was used

Gel extraction kit (Qiagen Inc.) the desired product was isolated from a 1.5% agarose gel

A 500bp DNA fragment (FIGS. 1A-1B). This EcoRI/BamHI fragment was ligated into pRIT2 which had been linearized with EcoRI/BamHI using T4 ligase. XLL-Blue competent cells were transformed with the ligation mixture and transformed colonies were selected on LB agar plates containing 100mg/L ampicillin. The successfully obtained construct containing the DNA insert was designated pCBD-ProtAl.

Expression and purification of CBD-ProtA

Expression of the fusion protein was carried out as described in the literature (Nilsson et al (1985) EMBO J.4(4): 1075-1080). 400ul of E.coli strain 2097 containing pCBD-ProtAl was inoculated overnight into 40ml of LB containing 50mg/L ampicillin. The cultures were grown to 100Klett (green filter) at 30 deg.C, incubated 45 minutes at 42 deg.C with temperature change, and then incubated for an additional 2 hours at 40 deg.C. Cells were harvested by centrifugation at 2,000g for 10 minutes and then resuspended in 10ml of 20mM Tris-HCl buffer (pH 7). Sonication was performed using a W-385 sonicator (Heat Systems-ultrasonics, Inc.) at maximum power for 1 minute, followed by cooling for 30 seconds, and this was repeated 3 times to disrupt the cells. The lysate was centrifuged (4,000g,10 min) to give a clear solution and 500mg of cellulose particles (Sigmacell 20, average particle size 20 μm) were added. The suspension was incubated at room temperature for 10 minutes and centrifuged (2,000g,10 minutes). The supernatant was removed and the pellet was washed 1 time with 5ml of 1M NaCl to remove non-specifically bound proteins and then 2 times with 10ml of deionized water. CBD-ProtA was removed from cellulose with 5ml 6M guanidine hydrochloride. After centrifugation (2,000g,10 min), the resulting solution was dialyzed against 20mM Tris-HCl buffer (pH7) and the proteins were analyzed on 12.5% SDS-PAGE as described by Laemmli (1970).

Binding assay for CBD-ProtA

CBD-ProtA was tested for binding to IgG as follows: mu.l of a suspension of rabbit IgG (H + L) -Sepharose (8mg/ml, Bio-Makor Inc.) which had been prewashed with PBS (phosphate buffered saline pH7.4) was mixed with 1ml of isolated CBD-ProtA (50. mu.g/ml). The mixture was incubated at 8 ℃ for 1 hour and then centrifuged (2,000g,5 min). The supernatant was removed and the pellet was washed twice with 500. mu.l PBS. Then, CBD-ProtA was eluted with 200. mu.l of 1M acetic acid. The pellet was mixed with 15. mu.l of loading buffer (SAB; 125mM Tris-HCl pH6.8, 4% SDS, 20% glycerol and 0.002% bromophenol blue), and 15. mu.l of samples of the different fractions were mixed with 15. mu.l of SAB, then boiled for 5 minutes and analyzed on SDS-PAGE.

The binding of CBD-ProtA to cellulose was tested as follows: 20mg of cellulose (Sigmacell 2D) was mixed with 200. mu.l of isolated CBD-ProtA (50. mu.g/ml). The mixture was incubated at room temperature for 15 minutes and centrifuged at 2,000g for 5 minutes. After washing the pellet with 200. mu.l of 1M acetic acid, it was resuspended in 40. mu.l of SAB. The suspension was boiled with 15. mu.l of wash (mixed with 15. mu.l of SAB) and analyzed on SDS-PAGE.

The results show that CBD-ProtA can be expressed in E.coli and purified in a one-step purification using cellulose. The fusion protein has the desired molecular size, i.e. 45kDa (fig. 3). CBD-ProtA retains its affinity for cellulose and IgG. 1M acetic acid has been shown to isolate the CBD-ProtA IgG linkage but not the CBD-ProtA: a cellulose linkage.

Using the expression vector, we were able to produce 6mg of CBD-ProtA per liter of culture, and our experience with the T7 overexpression system was able to produce more than 10 times more pure CBD (70mg/L, FIG. 9).

Cloning of CBD-HSP fusion proteins.

An example of cloning a CBD-NSP fusion protein is as follows: PCR primers for amplifying HSP genes were prepared using plasmid SJ60 as a template. This plasmid is described by Jendal et al (1989) mol.cell.biol.9: 2279). The primers contained a KpnI site at the N-terminus of the HSP and a stop codon at the C-terminus followed by a BamHI site.

A forward primer: 5' -ACGGTACCACTTCGGTTACCCACAGTC-3

Reverse primer: 5' -GGGGATCCTACATGCCACCTCCCATTAG-

To enable the C-terminal transcriptional fusion of the CBD to the N-terminus of the HSP, we introduced a KpnI site at the 3' end, which was used to perform CBD PCR amplification using PET-CBD as template and the following primers:

a forward primer: 5' -GTATACCAGCCATGGCAGCG-3

Reverse primer: 5' -GTACATCTGGATCCTATGGTACCGT-3

The amplified DNA was digested with Nco I and BamH I and ligated into Nco I/BamH I predigested pET-8c vector. XLL-Blue was then transformed with the ligation mixture and the new plasmid was named pET-CBDK. This plasmid was digested with KpnI/BamHI and ligated with HSP-PCR amplified fragment restricted with KpnI/BamHI: transformation into XLL-Blue and, after further confirmation, transformation of BL21(DE3) with this construct to overproduce CBD-HSP.

NH₂-VH-VL-CBD-CO₂Construction of

Cloning of the required V Using the "Recombi antibody System" ("Recombi antibody body System") (Pharmacia Inc.)_H-V_LFusion of the CBD with the recombinant antibody was completed. Using the resulting carrier V_H-V_LThe pCANTAB5 plasmid was used as a template for PCR amplification with the following primers:

a forward primer: 5' -AGCCATGGCGGCCCAGC-3

Reverse primer: 5' -GGGGTACCAACAGTTTGTGCGGCC-3

These primers introduce an NcoI site at the 5 'end of VH-VL and an NcoI site at the 3' end

The KpnI site was inserted. The amplified fragment was digested with Nco I and Kpn I and used in CBD as follows

In expression vectors fused at the C-terminus.

To transcriptionally fuse the N-terminal part of the CBD to V_H-V_LAt the C-terminal part of (i)

These introduced a KpnI site at the 3' end of the cbd gene. This introduction was accomplished by PCR amplification ofCBD using pET-CBD as template and the following primers:

a forward primer: 5' -GGGCCATGGCAGGTACCTCATCA-3

Reverse primer: 5' -GTACATCTGGATCCTATGGTGCTGT-3

These primers introduce a KpnI site into cbd gene after the 5 'terminal NcoI site, and retain the 3' terminal stop codon, followed by a BamHI site, and the amplified DNA was digested with NcoI and BamHI and ligated to NcoI/BamHI digested pETSC vector. The connecting mixture is used to transferXLlBlue was digested and this new plasmid was named pET-KCBD. The plasmid was digested with NcoI and KpnI and with NcoI/KpnI restriction enzyme V_H-V_LThe amplified fragments were ligated and converted to XLlBlue. Once this structure has been confirmed, it can be used to convert BL21(DE3) to produce excess V_H-V_L-CBD) fusion protein.

From the above disclosed and generally known in the art perspectives, it is apparent to one of ordinary skill in the art that a variety of CBD fusion products comprising a CBD and a second known sequence of a protein can be prepared.

IgG purification with CBD-ProtA cellulose

This example demonstrates the purification of IgG using CBD. Human serum (500. mu.l, 1:10) diluted in Phosphate Buffered Saline (PBS) (pH7.4) was added to 20mg of CBD-ProtA-cellulose suspension (4. mu.g/mg). The mixture was incubated at 8 ℃ for 1 hour, then rapidly centrifuged and washed twice with 500. mu.l PBS to remove unbound protein. IgG was recovered by washing with 200. mu.l of 1M acetic acid (15 min at room temperature), while CBD-ProtA remained bound to cellulose.

Characterization of CBDs

This example demonstrates that CBD does not destroy cellulose. CBD has no activity for cellulose destruction/amorphization to occur. Approximately 1mg of CBD was mixed with 10mgeach of two different types of cellulose (cotton and Cellulon) in 20mM Tris-HCl buffer pH7^_) Incubate at 37 ℃ overnight. The cellulose samples were coated with gold and observed under scanning electron microscopy. FIGS. 14A and 14B clearly demonstrate that CBD treated fibers compared to control untreated cottonThe cellulose remains intact.

The effect of pH and NaCl concentration on the binding capacity of CBD-ProtA on cellulose was examined. Mu.l of CBD-ProtA (100. mu.g) were added to tubes containing 550. mu.l of different buffers containing different concentrations of NaCl, i.e.0, 0.25, 0.5, 1M NaCl, 1mg cellulose (Sigmacell 20) and 1mg BSA. The tubes were incubated at 37 ℃ for 1 hour with occasional mixing and were weighed at 10,000g for 5 minutes. The precipitates were washed twice with their respective buffers. Add 40. mu.l of 6M guanidine hydrochloride to the suspended pellet and incubate at room temperature for 30 minA clock. After centrifugation, 780. mu.l of ddH was used₂20 μ l samples were diluted O and protein concentration was determined using the BioRad kit. FIG. 15 shows that at low pH, increasing NaCl concentrations increased the binding of CBD-ProtA to cellulose, so as to reach 70mg/g cellulose.

CBD alters growth of plant tissue

Plant material

Flowers of peaches (Prunus persica CV. Texas) were obtained from Rehovot's nursery. Anthers gathered from flowers were cut off from the filaments on day 1 of the flowering period and dehydrated at 30 ℃ for at least 24 hours. The released pollen can be used fresh or stored at-20 ℃. Seeds of Arabidopsis thaliana were obtained from University Stock.

In vitro pollen germination

Pollen grains were germinated in Eppendorf tubes containing 100. mu.l each of a liquid culture of growth medium. The growth medium was prepared as follows: subjecting the peach pollen grains to a treatment comprising 15% (w/v) sucrose, 100. mu.g/ml H3BO3, 200. mu.g/ml MgSO₄7H₂O and 200. mu.g/ml Ca (NO)₃)₂·4H₂And O in growth medium. Various concentrations of CBD or BSA were added to the tubes. The number of pollen grains in each tube was about 1,000. Each treatment was performed in triplicate. After incubation overnight at 25 ℃ in a dark chamber,pollen was tested in a population of a minimum of 100 pollen grains in each sample (300 grains per treatment).

Seed germination

Washing the seeds of Arabidopsis thaliana in distilled water. About 100 seeds of each treatment were immersed in 1ml of distilled water added to a glass culture tube having a diameter of 2cm and a length of 10 cm. The culture tubes were placed in a growth chamber at a constant temperature of 25 ℃ and a light/dark period of 16/8 hours, respectively, was applied. After 4 days, the length of the seedlings, stems, roots and root hairs (longest in each seedling) was measured to examine the effect of the different treatments on the plant organs.

Histochemical study

The overnight growth medium was fixed with 4% glutaraldehyde in 0.1M phosphate buffer (pH7.4) at 10,000g for 1 minute, and the cultured peach pollen tube with or without CBD was washed out from the growth medium. The pollen tube was washed with the same buffer and then carefully suspended in the same volume of 4% glutaraldehyde in the same buffer and left overnight at 4 ℃. The pollen tube was again centrifuged, washed with the same buffer, then with distilled water, and then with a fluorescent whitening agent (calcofluor, 0.1% at 0.1M K)₃PO₄) Staining to reveal crystalline cell wall components. Microscopic observation was performed with a yellow light microscope (RA Zeiss Oberkochen). Arabidopsis (Arabidopsis) seedlings were treated in the same manner, but the solution was changed so that no precipitation occurred.

Peach pollen tubes and arabii dopsis seedlings were examined by immunogold-silver staining (IGGSS) to demonstrate the binding of CBD to cellulose. First, the mixture was added to PBST (phosphate buffered saline TWEEN 2)^TM) The plant material was fixed overnight with 4% glutaraldehyde (v/v). The samples were washed with PBST for 1 hour, soaked in 1% skim milk for 1 hour, and then incubated with polyclonal rabbit anti-CBD antibody diluted 1: 500 in PBST for 1 hour. Samples were washed for 3X 10 minutes in PBST and then incubated for 1 hour with goat anti-rabbit IgG-linked with 5nm gold particles diluted 1: 100 in PBST. The samples were washed with PBST for 2X 10 minutes and then 1 time in water. The reaction was terminated using a silver staining kit (BioCell Research Laboratories)And (4) developing color. The sample was immersed in the combined solution of the kit for about 10 minutes and then washed with enough distilled water. The samples were observed under an optical microscope.

Effect of CBD on pollen tube growth

FIG. 19 shows the effect of CBD on pollen tube length compared to BSA (control protein). Different letters indicate a substantially significant difference between the pollen tube length values (P ≦ 0.05). This demonstrates that CBD promotes pollen tube growth. BSA may inhibit pollen tube growth by osmosis. In this respect, the results obtained at a concentration of 50. mu.g/ml are most pronounced, wherein CBD-treated pollen produced pollen tube growth that was almost 2 times that of pollen treated with 50. mu.g/ml BSA.

In an attempt to examine the mode of action of CBD, pollen tubes (CBD treated and control) were stained with fluorescent whitening agent (calcofluor) to reveal crystalline cell wall components. FIGS. 20A and 20B demonstrate that CBD treated pollen tubes produced non-crystalline pollen tube apical buds as shown by the absence of bright color in the apical bud region. The absence of a rigid crystalline cell wall in the apical bud region may facilitate pollen tube elongation. Gold-immunolabeling of CBD-treated pollen tubes demonstrated that CBD was bound along the pollen tube as evidenced by dense dark spots on the apical bud region. In addition, it is strongly suggested that the absence of a rigid crystalline cell wall in the apical bud region is due to CBD. One possible mechanism is that the CBD intercalates with the cellulose fibers formed, thereby inhibiting the crystallization process.

Effect of CBD on root and root Hair growth

The effect of CBD on root growth of Arabidopsis thaliana (Arabidopsis thaliana) seedlings was examined, and the results are shown in FIG. 22. At high concentrations, CBD significantly reduced root length, while a smaller concentration (100 μ g/ml) of BSA had no effect. Different letters indicate a substantially significant difference between root length values (<0.05). The effect on stem length showed a similar trend, but was not as pronounced as the effect on roots and was not of substantial significance. Gold-immunolabeling of CBD-treated Arabidopsis thaliana seedlings (FIG. 23) showed that gold labeling was restricted to roots, whereas no labeling was shown on shoots. Staining of Arabidopsis thaliana (Arabidopsis thaliana) seedlings with a fluorescent whitening agent (calcofluor) showed that only accessible cellulose roots were stained (fig. 24). The lack of bright color on the stem indicates that the stain did not penetrate the waxy cuticle, explaining why CBD was effective on roots and not on stems.

High concentration (1X 10)^-6To 1X 10^-4μ g/ml) the inhibitory effect of CBD on root elongation can be explained as a steric hindranceof the cellulose, preventing it from accessing enzymes like endo-glucanase or xyloglucanotransferase or proteins regulating cell elongation by loosening the strong cellulose fiber network. At low concentrations, CBD may increase the crystallinity of the cell wall, orThis interferes with the xyloglucan cellulose interaction, thereby preventing cross-linking of the cellulose network.

These results described herein clearly demonstrate that CBD fusion proteins can be used for affinity purification of proteins and enzymes using cellulose as a soluble solid phase matrix. Furthermore, based on the above disclosure, it will be apparent to those of ordinary skill in the art that CBD fusion products have a wide range of potential applications, including but not limited to affinity purification methods and use in diagnostic kits.

Deposit of microorganisms

The following microorganisms were deposited at the American Type Culture Collection (ATCC) (12301 Parklawn Drive, Rockville, Md.) at 12.4.1993 and given the accession numbers indicated below:

microbial registration number

-- --

E.coli pCBD-ProtA1/2097 69283

F.coli pET-CBD/BL21(DE3) 69282

E.coli pCBD-ProtA1 75443

E.coli pET-CBD 75444

The invention described and claimed herein is not to be limited in scope by the specific embodiments, which are intended as illustrations of several aspects of the invention. Any equivalent embodiments will also fall within the scope of the present invention. In addition to the examples shown and described herein, various modifications will be apparent to those skilled in the art from the foregoing description. Such modificationsare intended to fall within the scope of the appended claims.

It is also understood that all given nucleotide and peptide base pair and amino acid residue numbers and sizes are approximate and are used for descriptive purposes only.

Many of the references cited herein are incorporated by reference in their entirety as if fully set forth herein.

International Application No:PCT/

Form PCT/RO/134 (January 1981)

International Application No:PCT//

Form PCT/RO/134(cont.)

American Type Culture Collection

12301 Parklawn Drive

Rockville,MD 20852

US

Accession No. Date of Deposit

69283 April 12,1993

75443 April 12,1993

75444 April 12,1993

Claims (31)

1. A diagnostic kit for detecting a substance of interest comprising:

(a) a Cellulose Binding Domain (CBD) fusion product comprising (i) a CBD,

the amino acid sequence of which consists of the amino acid sequence of FIGS. 1A-1B, or ATCC accession

The vector, designated No.75444, is encoded and is capable of binding with high affinity to cellulose,

and substantially free of other proteins with which it is naturally associated; and (ii) capable of combined feel

A second protein of the substance of interest;

(b) a detectable label; and

(c) cellulose.

2. A diagnostic kit according to claim 1 wherein said cellulose is replaced by chitin.

3. A diagnostic kit according to claim 1 or 2 wherein said second protein is protein a or an enzyme.

4. A diagnostic kit according to claim 1 or 2, wherein said second protein is an HSP protein, an HSP antibody, an HSP-related protein, a peptide or antigenic parts thereof.

5. A diagnostic kit according to claim 1 or 2, wherein said cellulose binding domain fusion product further comprises a ligand that binds with affinity to said second protein, said ligand being capable of binding said substance of interest.

6. A diagnostic kit according to claim 5 wherein said ligand is an antibody.

7. A method of detecting the presence of a substance of interest in a test sample, the method comprising:

(a) in the area (CBD) allowing the binding of said substance of interest to said cellulose

The fusion product will likely contain the substance of interest under conditions in which the second protein binds

Is incubated with a sufficient amount of a CBD fusion product comprising

(i) a cellulose binding domain having an amino acid sequence corresponding to the amino acid sequence of figures 1A-1B

Or at least 80% as compared to the CBD expressed by the vector with ATCC accession number 75444

And is capable of binding to cellulose or chitin with high affinity, and

substantially free of other proteins with which it is naturally associated, and (ii) capable of associating with said

A second protein to which the substance of interest binds;

(b) combining the test sample and the cellulose binding domain fusion product with an amount of cellulose or

Contacting chitin effective to bind to an amount of said CBD fusion product used in step (a) to provide a bound complex of insoluble cellulose-cellulose or chitin-cellulose binding domain fusion products;

(c) separating said insoluble cellulose-cellulose or chitin-cellulose binding domain fusion product bound complex from unbound components;

(d) incubating said insoluble cellulose-cellulose or chitin-cellulose binding domain fusion product binding complex with a sufficient amount of a detectable label capable of binding said substance of interest; and

(e) separating said insoluble cellulose-cellulose or chitin-cellulose binding domain fusion product binding complex of step (d) from unbound components and determining the presence or absence of said label to provide an indication of the presence or absence of said substance of interest in said test sample.

8. A method of detecting the presence of a substance of interest in a test sample, the method comprising:

(a) contacting a test sample which may contain a substance of interest with an insoluble matrix capable of immobilizing said substance of interest;

(b) incubating said insoluble substrate with a sufficient amount of a CBD fusion product under conditions which permit binding of said immobilized substance of interest to said second protein of said Cellulose Binding Domain (CBD) fusion product, wherein said fusion product comprises (i) a cellulose binding domain having an amino acid sequence which has at least 80% sequence similarity to the amino acid sequence of figures 1A-1B, or CBD expressed from the vector having ATCC accession No.75444, and which is capable of binding cellulose or chitin with high affinity and is substantially free of other proteins to which it naturally binds, and (ii) a second protein capable of binding said immobilized substance of interest;

(c) separating said insoluble matrix of step (b) from unbound components;

(d) incubating said insoluble matrix of step (c) with a detectable label capable of binding to said substance of interest, said CBD fusion product or cellulose or chitin under conditions permitting binding of said label to said substance of interest or said CBD fusion product or cellulose or chitin; and

(e) separating said insoluble matrix of step (d) from unbound fractions and determining the presence or absence of said label to provide an indication of the presence or absence of said substance of interest in said test sample.

9. The method of claim 8, further comprising after step (C): contacting the insoluble matrix of step (c) with a sufficient amount of cellulose or chitin under conditions permitting binding of said cellulose or chitin to said cellulose-binding domain fusion product to form a bound complex of cellulose-cellulose or chitin-cellulose binding domain fusion product, and (ii) separating the insoluble matrix of step (i) from unbound components, including unbound cellulose or chitin.

10. The method according to claim 8, wherein said label iscapable of binding to said substance of interest or to said cellulose binding domain fusion product.

11. The method according to claim 9, wherein said label is capable of binding to cellulose or chitin in a substance of interest or in a binding complex of said cellulose-cellulose or chitin-cellulose binding domain fusion protein.

12. The method of claim 7,8, 9, 10 or 11, wherein said test sample comprises a bodily fluid.

13. A method according to claim 8 or 9, wherein said insoluble matrix is an electrophoretic gel blot.

14. The method according to claim 7,8 or 11, wherein said substance of interest is a protein or peptide and said second protein is an antibody against said protein or peptide.

15. The method according to claim 7,8 or 11, wherein said substance of interest is an antibody and said second protein is protein a.

16. The method according to claim 7,8 or 11, wherein said substance of interest comprises a biotinylated probe bound to a protein, peptide, hormone, nucleic acid or other detectable target probe molecule, and said second protein is streptavidin.

17. The method according to claim 7,8, 9 or 11, wherein said label comprises a radioisotope, a fluorescent molecule, an enzyme, a chemiluminescent agent, an enzyme substrate or cofactor, an enzyme inhibitor or a particle.

18. The method according to claim 11, wherein said label comprises a cellulose bindingdomain fusion product comprising a cellulose binding domain and alkaline phosphatase.

19. The method according to claim 11, wherein said label comprises a fusion product of a cellulose binding domain comprising a cellulose binding domain and horseradish peroxidase.

20. The method according to claim 18 or 19, further comprising adding a sufficient amount of a substrate for said enzyme, said substrate being converted by said enzyme to a detectable compound.

21. A method of detecting the presence of a substance of interest in a test sample, the method comprising:

(a) in a zone (CBD) allowing the binding of said substance of interest to said cellulose

Combining the test sample with a sufficient amount of said second protein of the fusion product under conditions such that said second protein binds to said test sample

Incubating the CBD fusion product together, wherein said fusion product comprises (i) a cellulose nodule

A synthetic region having an amino acid sequence corresponding to the amino acid sequence of FIGS. 1A-1B, or ATCC

The CBD expressed by the vector with accession number 75444 has an amino acid sequence of at least 80%

Sequence similarity and ability to bind with high affinity to cellulose or chitin, and

substantially free of other proteins with which it is naturally associated, and (ii) capable of binding said

A second protein of the substance of interest;

(b) combining the test sample and the cellulose binding domain fusion product withan amount of cellulose or a shell

Contacting the polysaccharide so that it effectively binds a quantity of said CBD used in step (a)

Fusing the product to provide insoluble cellulose-cellulose or chitin-cellulose binding domains

A binding complex of a domain fusion product;

(c) separating said insoluble cellulose-cellulose or shell from unbound components

A binding complex of a polysaccharide-cellulose binding domain fusion product;

(d) combining said insoluble cellulose-cellulose or chitin-cellulose domains

The binding complex of the fusion product is incubated with a sufficient amount of a detectable label, said label

The label comprises a substance of interest which is labelled, said label being capable of binding to said cellulose

Any second protein that binds to the domain fusion product, which does not bind to the substance of interest;

and

(e) separating said insoluble cellulose of step (d) from unbound components

A binding complex of cellulose or chitin-cellulose binding domain fusion product, and a polypeptide derived from the same

The signal observed in the test sample is compared to the signal observed from the control sample.

22. A method according to claim 7, wherein said cellulose binding domain fusion product is contained in a dip stick (dip stick).

23. A signal amplification kit comprising:

(a) a first Cellulose Binding Domain (CBD) fusion product comprising:

CBDs having amino acid sequences represented by the group of amino acid sequences shown in FIGS. 1A-1B

To make, and

(ii) a second protein capable of binding to a chimeric probe capable of binding to a second protein

Capable of further binding to a protein of interest;

(b) a chimeric probe;

(c) a second CBD fusion product comprising (i) a CBD whose amino acid sequence is as shown

1A-1B, and (ii) capable of acting on a substrate to produce

An enzyme capable of detecting the compound.

24. A signal amplification kit according to claim 23, further comprising a substrate for said enzyme in said second CBD fusion product.

25. A signal amplification kit comprising:

(a) a Cellulose Binding Domain (CBD) fusion product comprising:

a CBD whose amino acid sequence consists of the amino acid sequence of figures 1A-1B,

and

(ii) a second protein capable of binding to a chimeric probe, said probe being capable of binding to

Binding the substance of interest in one step; and

(b) a labelled CBD, the amino acid sequence of which consists of the amino acids of figures 1A-1B

The amino acid sequence.

26. A signal amplification kit comprising a Cellulose Binding Domain (CBD) fusion product, comprising:

a CBD whose amino acid sequence consists of the amino acid sequence of figures 1A-1B, and

(ii) a second protein capable of binding a third protein, said third protein

Capable of further binding to a protein of interest, and

(iii) a third protein.

27. A signal amplification kit according to claim 26, further comprising a labeled CBD, the amino acid sequence of said CBD consisting of the amino acid sequences of figures 1A-1B.

28. A signal amplification kit according to claim 23, 25 or 26, further comprising pebbled milled cellulose.

29. The signal amplification kit according to claim 23, wherein said probe is biotinylated and said second protein is streptavidin.

30. A signal amplification kit according to claim 23, wherein said enzyme in said second fusion product is selected from the group consisting of alkaline phosphatase and horseradish peroxidase.

31. A signal amplification kit according to claim 25 or 26, wherein the labelled CBD comprises a CBD and a radioisotope, fluorescent molecule or enzyme.

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