CN108129557B

CN108129557B - Cadmium binding protein A2XYI5 and application thereof

Info

Publication number: CN108129557B
Application number: CN201711387982.4A
Authority: CN
Inventors: 魏帅; 郭波莉; 魏益民; 孙倩倩
Original assignee: Institute of Food Science and Technology of CAAS
Current assignee: Institute of Food Science and Technology of CAAS
Priority date: 2017-12-20
Filing date: 2017-12-20
Publication date: 2021-10-29
Anticipated expiration: 2037-12-20
Also published as: CN108129557A

Abstract

The invention discloses a cadmium binding protein A2XYI5 and application thereof. The invention firstly discloses rice-derived cadmium binding protein A2XYI5, the amino acid sequence of which is shown in SEQ ID No. 1. The invention further discloses a gene for coding the cadmium binding protein, and the nucleotide sequence of the gene is shown in SEQ ID No. 2. The cadmium-binding protein A2XYI5 gene is heterologously expressed in escherichia coli, and the recombinant strain can quickly and efficiently reduce the content of cadmium under the condition of the presence of heavy metal cadmium. The invention further discloses application of the metal cadmium binding protein or the coding gene thereof in the aspects of repairing cadmium-polluted soil, cultivating a new plant variety with improved cadmium resistance, cultivating a new plant variety with cadmium super-enrichment, reducing cadmium content in rice and the like.

Description

Cadmium binding protein A2XYI5 and application thereof

Technical Field

The invention relates to a rice (Oryza sativa) sourced cadmium binding protein, and also relates to application of the cadmium binding protein in adsorption and degradation of cadmium, remediation of cadmium contaminated soil and reduction of cadmium content in rice, belonging to the field of separation and application of the rice sourced cadmium binding protein.

Background

Cadmium is one of heavy metals with the strongest toxicity, and the cadmium pollution problem of grains and vegetables is increasingly prominent due to the fact that farmland soil in some regions is polluted to different degrees due to human activities. Statistically, about 114 million hectares of land in China are contaminated with cadmium, with a cultivated area of 1.3 million hectares, involving 25 areas of 11 provinces (cities). The 2010 statistics yearbook data shows that the annual output of the Chinese paddy is about 2 hundred million tons, the produced rice is about 1.3 hundred million tons, and if the cadmium of 10 percent of rice exceeds the standard according to early sampling inspection, the cadmium of 1300 ten thousand tons of rice exceeds the standard. The serious cadmium exceeding problem of the rice becomes a serious hidden danger and a grain safety risk of grain safety and even social stability. The research aiming at the cadmium pollution of rice mostly focuses on soil improvement, low-enrichment rice variety screening, later-period processing of cadmium-polluted rice and the like. Among them, the soil improvement technology is the most important repair method in the top stream. At present, the main soil improvement technology adopts a physical and chemical remediation technology, which is often accompanied by the problems of high energy consumption, high cost, secondary pollution and the like, so that the method is not suitable for the remediation of the large-scale polluted soil. In recent years, bioremediation methods for remedying contaminated soil by using plants and microorganisms have attracted much attention because of their advantages of environmental friendliness, high efficiency, low cost, and the like.

Plants and microorganisms with super-enriched heavy metals are often used in bioremediation methods, but most plants enriched in heavy metals grow slowly and require a specific growth environment, and the super-enriched microorganisms face competition with soil indigenous microorganisms in the soil contaminated by the addition of heavy metals. Therefore, the problem can be solved by utilizing a genetic engineering method to heterologously express the metal binding protein gene in plants and microorganisms with good growth vigor and strong adaptability, so that the plants and microorganisms which are not originally super-enriched in heavy metals become the plants and microorganisms super-enriched in heavy metals. For example, in 2000, Valls et al, which displayed the mouse-derived metallothionein gene (mts) on the surface of the bacterium Ralstonia eutropha CH34, constructed an engineered strain to immobilize heavy metal ions in soil, showed that the engineered strain could immobilize 70% of cadmium in soil so that it was not absorbed by plants when the soil cadmium concentration was 150. mu. mol (Valls, Nature biotechnology, 2000). Metallothionein MTs are one of metal binding proteins, and are called metallothionein because of low molecular weight and high sulfhydryl content, and can bind a large amount of heavy metal ions. MTs were first isolated from the kidney of horses in 1957 by Margoshes and Vallee, Harvard university, USA, after which the protein was found to be widespread in animals, plants and microorganisms.

MTs are generally found to have a high degree of amino acid sequence similarity, due to the structural features of MTs including homocysteine and the lack of aromatic amino acids, and cysteine residues responsible for their high affinity binding capacity to metal ions. The cadmium binding protein derived from rice is separated and identified, the cadmium content in rice is reduced by using a heterologous expression cadmium binding protein gene, and the method is safe and reliable.

Disclosure of Invention

The first technical problem to be solved by the invention is to provide a rice-derived cadmium binding protein and a coding gene thereof;

the second technical problem to be solved by the invention is to provide the application of the rice-derived cadmium binding protein in reducing the cadmium content in rice.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

the invention firstly discloses rice-derived cadmium binding protein A2XYI5, the amino acid sequence of which is shown in SEQ ID No. 1.

Metallothionein MTs have been found to have generally high amino acid sequence similarity. The protein sequence and amino acid composition of the rice-derived cadmium metal binding protein A2XYI5 are greatly different from those of the existing MTs.

The invention further discloses a gene for coding the cadmium metal binding protein A2XYI5, wherein the polynucleotide sequence of the gene is shown in (a), or (b) or (c):

(a) and a polynucleotide sequence shown in SEQ ID No. 2; or

(b) A polynucleotide sequence which hybridizes with the complementary sequence of SEQ ID No.2 under stringent hybridization conditions, wherein the polynucleotide encodes a protein which still has the function or activity of binding cadmium; or

(c) Polynucleotide sequence with at least more than 80% homology with the polynucleotide sequence of SEQ ID No.2, and the protein coded by the polynucleotide still has the function or activity of binding cadmium; preferably, the polynucleotide sequence has at least more than 85% homology with the polynucleotide sequence of SEQ ID No.2, and the protein coded by the polynucleotide still has the function or activity of binding cadmium; more preferably, the polynucleotide sequence has at least 90% homology with the polynucleotide sequence of SEQ ID No.2, and the protein encoded by the polynucleotide still has the function or activity of binding cadmium.

The invention also discloses a recombinant vector containing the gene for coding the cadmium metal binding protein A2XYI 5. The recombinant vector is a recombinant expression vector or a recombinant cloning vector.

The invention also discloses a recombinant host cell or a recombinant bacterium containing the gene for coding the metal cadmium binding protein A2XYI 5. Wherein, the recombinant bacteria include but are not limited to recombinant Escherichia coli.

In order to further verify whether the separated and identified cadmium metal binding protein A2XYI5 has the function of binding cadmium, the invention constructs a protein gene sequence on an escherichia coli expression vector, transfers the protein gene sequence into an escherichia coli expression strain to construct a recombinant strain A2xyi5-pET30a: delta zntA-BL21, and evaluates the function of the gene by measuring the cadmium removal capacity of the recombinant strain. Meanwhile, the coding gene mt of mouse-derived metallothionein MTs is used as a reference gene to construct a recombinant strain mt-pET30a: delta zntA-BL 21. The results showed that the control strain had a cadmium removal rate of 13.61% while the recombinant strains a2xyi5-pET30a: Δ znA-BL 21 and mt-pET30a: Δ znA-BL 21 had cadmium removal rates of 50.78% and 47.47%, respectively, under the same culture conditions. The metallothionein MTs and the metal binding protein A2XYI5 both have cadmium binding capacity, and the binding capacity of the metal binding protein A2XYI5 from rice in Escherichia coli is stronger than that of the metallothionein MTs from mice, so that the metal binding protein A2XYI5 separated from rice can also play a role in cadmium binding.

To enter intoThe method comprises the steps of exploring the maximum binding capacity of the recombinant strain a2xyi5-pET30a delta zntA-BL21 cadmium, and measuring the residual amount of the cadmium under different cadmium concentration conditions. The results showed that the recombinant E.coli a2xyi5-pET30a: Δ zntA-BL21 was CdCl at 0.01mM, 0.03mM, 0.05mM, 0.07mM and 0.09mM₂Under the conditions, the cadmium binding concentration was 0.00647mM, 0.0185mM, 0.0268mM, 0.0265mM, and 0.0225mM, respectively. As a result, the maximum binding concentration of cadmium in the recombinant strain was about 0.026mM, and the medium was saturated with 0.05 mM.

Therefore, the separated metal cadmium binding protein or the encoding gene thereof can be applied to adsorbing or degrading heavy metal cadmium in soil, and the following application modes are provided specifically for reference:

(1) transforming the encoding gene of the metal cadmium binding protein A2XYI5 into a microbial strain to construct a recombinant engineering strain, and applying the recombinant engineering strain to soil to adsorb or degrade heavy metal cadmium in the soil; for example, the encoding gene of the cadmium metal binding protein A2XYI5 of the invention can be operably connected with a prokaryotic expression vector to construct a prokaryotic expression vector, the constructed prokaryotic expression vector is transformed into a microbial strain to obtain an engineering strain with cadmium binding performance, and the recombinant engineering strain is applied to soil containing cadmium to effectively adsorb or degrade the heavy metal cadmium in the soil, thereby achieving the effect of soil remediation.

(2) Cultivating a new cadmium-resistant plant variety: the metal cadmium binding protein A2XYI5 coding gene is transformed into plant cells or tissues, and a new plant variety with enhanced cadmium resistance is obtained by cultivation and screening; for example, the cadmium metal binding protein A2XYI5 encoding gene of the invention can be operably connected with a plant expression vector and then transformed into plant cells or tissues, and a new plant variety with enhanced cadmium resistance is obtained by breeding and screening; the plant comprises a monocotyledon or a dicotyledon; for example, it may be a crop such as corn, rice, barley, wheat, sorghum, etc.

(3) Cultivating a new plant variety with cadmium super-enrichment: the encoding gene of the metal cadmium binding protein A2XYI5 is transformed into plant cells or tissues, and a new plant variety capable of effectively enriching or adsorbing cadmium in soil is obtained by cultivation and screening; planting the new plant varieties with the cadmium super-enrichment property into the soil containing cadmium, and degrading or adsorbing the cadmium in the soil in a phytoremediation mode; for example, the cadmium metal binding protein A2XYI5 coding gene can be operably connected with a plant expression vector and then transformed into plant cells or tissues, new plant varieties with strong cadmium enrichment and large transport coefficient are obtained through cultivation and screening, and the new plant varieties with cadmium super-enrichment are planted in soil isolated from pollution to achieve the effect of soil remediation; the plant includes monocotyledons or dicotyledons.

In the present invention, any plant transformation method can be used to introduce the recombinant plant expression vector constructed in the present invention into cells, tissues or organs of a target plant to obtain a transformant; then regenerating the transformant by a plant tissue culture method to obtain a complete plant and a clone or a descendant thereof; the transformation method comprises the following steps: agrobacterium-mediated transformation, protoplast transformation, Ti plasmids, Ri plasmids, plant viral vectors, microinjection, electroporation, particle bombardment, and the like.

The chimeric gene or the expression cassette obtained by the chimeric or connected gene shown in SEQ ID No.2 of the invention and other genes belongs to the protection scope of the invention. The recombinant expression vector containing the chimeric gene or the expression cassette also belongs to the protection scope of the invention.

The transgenic plant cells and plants obtained by the methods disclosed herein may also be used further in subsequent transformation procedures, for example to introduce other chimeric genes.

The metal cadmium binding protein A2XYI5 derived from rice is derived from rice, and the metal cadmium binding protein gene is expressed by a heterologous way to reduce the cadmium content in rice, so that the method is safe and reliable.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

the invention discloses a rice-derived cadmium metal binding protein A2XYI5 with binding affinity for heavy cadmium metal. The invention expresses the cadmium binding protein gene in escherichia coli in a heterologous way, and can quickly and efficiently reduce the content of cadmium under the condition of heavy metal cadmium. The protein sequence and amino acid composition of the metal cadmium binding protein A2XYI5 from rice are greatly different from those of the existing metallothionein MTs, the protein is derived from rice, the cadmium content in rice is reduced by heterologously expressing the metal cadmium binding protein gene, and the protein is safe and reliable.

Definitions of terms to which the invention relates

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods, devices, and materials are now described.

The term "homology" refers to sequence similarity to a native nucleic acid sequence. "homology" includes a nucleotide sequence having preferably 85% or more, more preferably 90% or more, and most preferably 95% or more identity to the nucleotide sequence of the regulatory fragment of the present invention. Homology can be assessed visually or by computer software. Using computer software, homology between two or more sequences can be expressed as a percentage (%), which can be used to assess homology between related sequences.

The term "complementary" as used herein refers to two nucleotide sequences comprising antiparallel nucleotide sequences capable of pairing with each other upon hydrogen bonding between complementary base residues of the antiparallel nucleotide sequences. It is known in the art that the nucleotide sequences of two complementary strands are reverse complementary to each other when the sequences are viewed in both 5 'to 3' directions. It is also known in the art that two sequences that hybridize to each other under a given set of conditions do not necessarily have to be 100% perfectly complementary.

The term "stringent hybridization conditions" means conditions of low ionic strength and high temperature as known in the art. In general, Probes hybridize to their target sequences to a greater extent than to other sequences under stringent conditions (e.g., at least 2-fold over background. stringent Hybridization conditions are sequence-dependent and will differ under different environmental conditions, longer sequences hybridize specifically at higher temperatures. target sequences that are 100% complementary to Probes can be identified by controlling the stringency or wash conditions of Hybridization. for an exhaustive guidance of Nucleic acid Hybridization, reference is made to the relevant literature (Tijssen, Techniques in Biochemistry and Molecular Biology-Hybridization with Nucleic acid Probes, "Overview of primers of Hybridization and the analysis of Nucleic acid assays.1993. more specifically, stringent conditions are generally selected to be about 5-10 ℃ below the thermal melting point (Tm) of a specific sequence at a defined ionic strength pH. the temperature at which 50% of a probe is 50% complementary to a target sequence in equilibrium (the ionic strength at the specified ionic strength), pH and nucleic acid concentration) (50% of the probes are occupied at equilibrium at Tm because the target sequence is present in excess). Stringent conditions may be as follows: wherein the salt concentration is less than about 1.0M sodium ion concentration, typically about 0.01 to 1.0M sodium ion concentration (or other salt) at pH 7.0 to 8.3, and the temperature is at least about 30 ℃ for short probes (including but not limited to 10 to 50 nucleotides) and at least about 60 ℃ for long probes (including but not limited to greater than 50 nucleotides). Stringent conditions may also be achieved by the addition of destabilizing agents such as formamide. For selective or specific hybridization, the positive signal can be at least two times background hybridization, optionally 10 times background hybridization. Exemplary stringent hybridization conditions may be as follows: 50% formamide, 5 XSSC and 1% SDS, incubated at 42 ℃; or 5 XSSC, 1% SDS, incubated at 65 ℃, washed in 0.2 XSSC and washed in 0.1% SDS at 65 ℃. The washing may be for 5, 15, 30, 60, 120 minutes or more.

The terms "mutation" and "mutant" have their usual meanings herein, and refer to a genetic, naturally occurring or introduced change in a nucleic acid or polypeptide sequence, which has the same meaning as is commonly known to those of skill in the art.

The term "host cell" or "recombinant host cell" means a cell comprising a polynucleotide of the invention, regardless of the method used for insertion to produce the recombinant host cell, e.g., direct uptake, transduction, f-pairing or other methods known in the art. The exogenous polynucleotide may remain as a non-integrating vector, such as a plasmid, or may integrate into the host genome.

The term "polynucleotide" or "nucleotide" means deoxyribonucleotides, deoxyribonucleosides, ribonucleosides, or ribonucleotides and polymers thereof in either single-or double-stranded form. Unless specifically limited, the term encompasses nucleic acids containing known analogs of natural nucleotides that have binding properties similar to the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise specifically limited, the term also means oligonucleotide analogs, which include PNAs (peptide nucleic acids), DNA analogs used in antisense technology (phosphorothioates, phosphoramidates, and the like). Unless otherwise specified, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (including, but not limited to, degenerate codon substitutions) and complementary sequences as well as the sequence explicitly specified. In particular, degenerate codon substitutions may be achieved by generating sequences in which the 3 rd position of one or more selected (or all) codons is substituted with mixed base and/or deoxyinosine residues (Batzer et al, Nucleic Acid Res.19:5081 (1991); Ohtsuka et al, J.biol.chem.260: 2605-S2608 (1985); and Cassol et al (1992); Rossolini et al, Mol cell. probes 8:91-98 (1994)).

The term "operably linked" refers to a functional spatial arrangement of two or more nucleic acid regions or nucleic acid sequences. For example, a promoter region may be positioned relative to a nucleic acid sequence encoding an expression product of interest such that transcription of the nucleic acid sequence is directed by the promoter region. Thus, a promoter region is "operably linked" to the nucleic acid sequence.

The term "transformation" as used herein refers to a process for introducing heterologous DNA into a plant cell, plant tissue, or plant. Transformed plant cells, plant tissues, or plants are understood to include not only the end product of the transformation process, but also the progeny thereof.

The terms "transformation", "transgene", and "recombinant" herein refer to a host cell or organism, such as a bacterial or plant cell (e.g., a plant), into which a heterologous nucleic acid molecule has been introduced. The nucleic acid molecule may be stably integrated into the genome of the host, or the nucleic acid molecule may also be present as an extrachromosomal molecule. Such an extrachromosomal molecule may be self-replicating. Transformed cells, tissues or plants are understood to include not only the end product of the transformation process, but also transgenic progeny thereof. A "untransformed", or "non-recombinant" host refers to a wild-type organism, such as a bacterium or a plant, which does not comprise a heterologous nucleic acid molecule.

The term "heterologous" refers to a relationship between two or more nucleic acid or protein sequences derived from different sources. For example, a promoter is heterologous with respect to an operably linked nucleic acid sequence (e.g., a coding sequence) if such a combination does not normally occur in nature. In addition, a particular sequence may be "heterologous" with respect to the cell or organism into which it is inserted (i.e., not naturally occurring in such particular cell or organism). For example, a chimeric gene disclosed herein is a heterologous nucleic acid.

The term "promoter" refers to any of the following nucleic acid sequences (e.g., DNA sequences): such sequences are recognized by DNA-dependent RNA polymerase during transcription initiation and bind (directly or indirectly) resulting in the production of RNA molecules complementary to the transcribed DNA; such regions may also be referred to as "5' regulatory regions". Promoters are typically located upstream of the 5' untranslated region (UTR) present in front of the coding sequence to be transcribed and have regions that serve as binding sites for RNA polymerase II and other proteins such as transcription factors to initiate transcription of an operably linked gene. The promoter itself may contain sub-elements (i.e., promoter motifs) such as cis-elements or enhancer domains that regulate transcription of an operably linked gene. The promoter and the linked 5' UTR are also referred to as "promoter regions".

Drawings

FIG. 1 is a flow chart of the construction of recombinant vector a2xyi5-pET30 a.

Detailed Description

The invention will be further described with reference to specific embodiments, and the advantages and features of the invention will become apparent as the description proceeds. It is to be understood that the described embodiments are exemplary only and are not limiting upon the scope of the invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be within the scope of the invention.

Example 1 isolation and characterization of Rice-derived cadmium binding protein A2XYI5

Rice seed (autumn field Xiaoting, provided by Shenyang agriculture university Rice research institute) Jing H₂O₂Soaking in 10% and 0.1% NaClO for 30min and 10h, respectively, cleaning with deionized water, placing in incubator at 30 deg.C, and culturing for 24 h. And (3) continuously culturing the seedlings in a quartz sand tray, and when a third leaf appears, selecting the seedlings with similar plant heights and transplanting the seedlings into 30L (30 multiplied by 40cm) soil pots, wherein each pot has 3 holes and each hole has 2 plants. The cadmium content of the soil is 100 mg/kg. After the rice is conventionally cultivated in a greenhouse to be mature, the rice roots are harvested. Cleaning, drying, grinding into powder, weighing 15g of dried root sample powder at room temperature, and extracting soluble protein with 150ml of aqueous solution of Tris-HCl.

Manufacturing a cadmium affinity column: the metal chelating affinity chromatography is an effective protein separation and purification method and the principle is to utilize Cu²⁺、Zn²⁺、Ni²⁺、Cd²⁺The transition metal ions are coordinated and combined with histidine, tryptophan or cysteine on the surface of the protein. The experiment adopts a metal chelating medium Ni-IDA, and uses a strong chelating agent 0.1mol/L EDTA solution to chelate Ni on the metal chelating medium²⁺Washing, and placing the medium without chelated metal ions in 0.05mmol/L Cd (NO)₃)₂Chelating Cd to the medium in the solution, washing off the free Cd with deionized water²⁺Obtaining the metal chelating medium Cd-IDA.

Loading the prepared Cd-IDA metal chelating medium into a column (

CV is 10.0mL), connecting to a chromatographic system, washing 5 column volumes by using IMAC equilibrium buffer solution, loading the prepared rice root protein sample at the flow rate of 0.5mL/min, stopping loading after the flow-through liquid is saturated, and removing buffer solution by using IMAC (0.05mol/L Tris-HCl +0.15mol/L NaCl)⁺0.5mol/L imidazole, pH 7.4), and the peak of the eluted protein was collected and, after further identification and analysis by mass spectrometry, the protein numbered A2XYI5 (the amino acid sequence of which is shown in SEQ ID No. 1) was obtained, which had a molecular weight of 27.306kDa and accounted for 5.32% of the total amount of rice root cadmium binding protein, and was a protein of unknown function (the uniprot database showed that purified unbound protein OS was organized zasatva subsp. japonica GN — OsI _17759PE 4SV 1).

Example 2 expression of cadmium binding protein Gene a2xyi5 in E.coli

In order to further verify whether the separated and identified cadmium-binding protein A2XYI5 has the function of binding cadmium, a protein gene sequence is constructed on an escherichia coli expression vector pET30a, the escherichia coli expression vector is transferred into an escherichia coli expression strain delta znA-BL 21, and whether the gene has the function is evaluated by measuring the cadmium removal capacity of a recombinant strain.

The protein sequence is subjected to transmembrane helix prediction before construction (prediction website http:// www.cbs.dtu.dk/services/TMHMM /), and amino acids 1 to 4 of the protein sequence are found in the membrane, transmembrane helix regions 5 to 27 are found, and regions 28 to 258 are located outside the membrane. In order to avoid difficult expression of membrane protein, a protein A2XYI 528-258 region is selected for synthesis, a gene sequence for coding the protein is synthesized in Nanjing Kingsler company after being optimized, and the gene sequence is shown as SEQ ID No. 2.

The synthesized gene a2xyi5 (the nucleotide sequence of which is shown in SEQ ID No. 2) is subjected to double digestion by restriction enzymes Kpn I and Xho I, meanwhile, the vector pET30a is subjected to double digestion by Kpn I and Xho I, and the recovered target fragment a2xyi5 and the vector pET30a are connected by T4DNA ligase. The specific construction process is shown in FIG. 1. The ligation system was transformed into E.coli competent cells TOP10 and positive clones were picked and sequenced by the sequencer. And (3) converting the clone seed extraction plasmid with correct sequencing into an escherichia coli expression strain delta znTA-BL21, and carrying out positive identification again. The obtained recombinant strain a2xyi5-pET30a: delta znA-BL 21 is used for evaluating the cadmium removal rate in the next step.

At the same time, the gene mt encoding mouse-derived metallothionein MTs, which is obtained from Valls, M., Atrian, S., de Lorenzo, V., Fern' e dez, L.A.engineering a mouse metallothionein on the cell surface of Ralstonia eutropha CH34for immunization of heav. biological in soil. biological technology 18,661 665 (2000). The gene is synthesized by Nanjing Kinshiri company after being optimized, and the gene sequence is shown as SEQ ID No. 3.

The recombinant strain mt-pET30a: delta znA-BL 21 is constructed at the same time according to the construction process of the recombinant strain a2xyi5-pET30a: delta znA-BL 21, and is also used for the next step of evaluating the cadmium removal rate.

In addition, the recombinant strain pET30a: delta znA-BL 21 is used as a negative control and is also used for evaluating the cadmium removal rate in the next step.

Example 3 evaluation of cadmium removal efficiency of recombinant E.coli a2xyi5/mt-pET30 a. DELTA. zntA-BL21

The recombinant strains a2xyi5-pET30a: Δ znA-BL 21 and mt-pET30a: Δ znA-BL 21 were inoculated in 3mL of 50 μ g/mL Kana-resistant LB liquid medium, cultured overnight at 37 ℃ at 200rpm, transferred to 50mL of 50 μ g/mL Kana-resistant LB liquid medium with an inoculum size of 1% the following day, and cultured with shaking at 37 ℃ at 200rpm for about 2h to OD₆₀₀Approximately equal to 0.6, the mixture is taken out, and added with IPTG at the final concentration of 0.1mM and CdCl at the final concentration of 0.05mM₂And taking out a proper amount of bacterial liquid after uniform mixing, immediately centrifuging at 13000rpm for 10min, and reserving the supernatant for measuring the cadmium content (the measured cadmium content is the initially added cadmium concentration). And (3) inducing the residual bacterial liquid at 30 ℃ and 200rpm for 12h, taking out and measuring the OD value and the cadmium residual content of the culture medium supernatant (the measured cadmium content is the cadmium residual concentration of the culture medium supernatant induced for 12 h). The cadmium content detection mode is as follows: taking a proper amount of thallus, centrifuging at 13000rpm for 10min, taking supernate, diluting the supernate with 0.6mM HCl with proper concentration, and measuring the residual cadmium content of the supernate by an atomic absorption spectrophotometer. Each treatment was 3 replicates.

The cadmium removal rate calculation formula is as follows:

cadmium removal rate C-100-A/B100

A is the residual cadmium concentration of the culture medium supernatant after 12h of induction;

b is the concentration of cadmium initially added to the medium.

The results are shown in Table 1.

TABLE 1 cadmium removal Rate of recombinant E.coli a2xyi5/mt-pET30 a:. DELTA.zntA-BL 21

As can be seen from Table 1, the control strain pET30a,. DELTA.zntA-BL 21, exhibited a cadmium removal rate of 13.61%, whereas the recombinant strain a2xyi5-pET30a,. DELTA.zntA-BL 21 and mt-pET30a,. DELTA.zntA-BL 21, exhibited cadmium removal rates of 50.78% and 47.47%, respectively, under the same culture conditions. The metallothionein MTs and the metal binding protein A2XYI5 both have cadmium binding capacity, and in Escherichia coli, the binding capacity of the metal binding protein A2XYI5 from rice is stronger than that of the metallothionein MTs from mice, so that the metal binding protein A2XYI5 from rice can also play a role in cadmium binding.

Example 4 evaluation of cadmium binding Capacity of recombinant E.coli a2xyi5-pET30 a. DELTA. zntA-BL21 under different cadmium concentrations

In order to further explore the maximum binding capacity of the recombinant strain a2xyi5-pET30a: Δ zntA-BL21 cadmium, the residual amount of cadmium under different cadmium concentrations was determined. The recombinant strain was first inoculated into 50. mu.g/mL Kana-resistant LB liquid medium, cultured overnight at 37 ℃ at 200rpm, transferred to 50mL 50. mu.g/mL Kana-resistant LB liquid medium with an inoculum size of 1% the next day, and cultured with shaking at 37 ℃ at 200rpm for about 2 hours to OD₆₀₀About.0.6, adding CdCl with final concentration of 0.1mM IPTG and final concentrations of 0.01mM, 0.03mM, 0.05mM, 0.07mM and 0.09mM respectively₂And taking out a proper amount of bacterial liquid after uniform mixing, immediately centrifuging at 13000rpm for 10min, and reserving the supernatant for measuring the cadmium content (the measured cadmium content is the initially added cadmium concentration). And (3) inducing the residual bacterial liquid at 30 ℃ and 200rpm for 12h, taking out and measuring the OD value and the cadmium residual content of the culture medium supernatant (the measured cadmium content is the cadmium residual concentration of the culture medium supernatant induced for 12 h). The cadmium content detection mode is as follows: taking appropriate amount of thallus, centrifuging at 13000rpm for 10min, taking supernatantThe residual cadmium content was determined by atomic absorption spectrophotometer after dilution with 0.6mM HCl at the appropriate concentration. Each treatment was 3 replicates.

The cadmium binding concentration calculation formula is as follows:

cadmium binding force D ═ A-B

b is the concentration of cadmium initially added to the medium.

The results are shown in Table 2.

TABLE 2 recombinant E.coli a2xyi5-pET30 a. DELTA. zntA-BL21 cadmium binding force under different cadmium concentrations

As can be seen from Table 2, recombinant E.coli a2xyi5-pET30a: Δ zntA-BL21 has CdCl at 0.01mM, 0.03mM, 0.05mM, 0.07mM and 0.09mM₂The cadmium binding concentrations under the conditions were 0.00647mM, 0.0185mM, 0.0268mM, 0.0265mM and 0.0225mM, respectively. As a result, the maximum binding concentration of cadmium in the recombinant strain was about 0.026mM, and the medium was saturated with 0.05 mM.

SEQUENCE LISTING

<110> institute for agricultural product processing of Chinese academy of agricultural sciences

<120> cadmium binding protein A2XYI5 and uses thereof

<130> BJ-2010-171107A

<160> 3

<170> PatentIn version 3.5

<210> 1

<211> 231

<212> PRT

<213> Rice

<400> 1

Thr Cys Gly Asp Gly Thr Tyr Glu Gln Gly Ser Ala Tyr Glu Asn Asn

1 5 10 15

Leu Leu Asn Leu Ala Leu Thr Leu Arg Asp Gly Ala Ser Ser Gln Glu

20 25 30

Ile Leu Phe Ser Thr Gly Ser Asn Gly Ala Ala Pro Asn Thr Val Tyr

35 40 45

Gly Leu Leu Leu Cys Arg Gly Asp Ile Ser Arg Ala Ala Cys Tyr Asp

50 55 60

Cys Gly Thr Ser Val Trp Arg Asp Ala Gly Ser Ala Cys Arg Arg Ala

65 70 75 80

Lys Asp Val Ala Leu Val Tyr Asn Glu Cys Tyr Ala Arg Leu Ser Asp

85 90 95

Lys Asp Asp Phe Leu Ala Asp Lys Val Gly Pro Gly Gln Leu Thr Thr

100 105 110

Leu Met Ser Ser Thr Asn Ile Ser Ser Gly Ala Asp Val Ala Ala Tyr

115 120 125

Asp Arg Ala Val Thr Arg Leu Leu Ala Ala Thr Ala Glu Tyr Ala Ala

130 135 140

Gly Asp Ile Ala Arg Lys Leu Phe Ala Thr Gly Gln Arg Val Gly Ala

145 150 155 160

Asp Pro Gly Phe Pro Asn Leu Tyr Ala Thr Ala Gln Cys Ala Phe Asp

165 170 175

Ile Thr Leu Glu Ala Cys Arg Gly Cys Leu Glu Gly Leu Val Ala Arg

180 185 190

Trp Trp Asp Thr Phe Pro Ala Asn Val Asp Gly Ala Arg Ile Ala Gly

195 200 205

Pro Arg Cys Leu Leu Arg Ser Glu Val Tyr Pro Phe Tyr Thr Gly Ala

210 215 220

Pro Met Val Val Leu Arg Glu

225 230

<210> 2

<211> 693

<212> DNA

<213> Rice

<400> 2

acctgtggcg atggtactta cgagcagggc agtgcttatg aaaataatct gttgaacctg 60

gcattaacat tacgcgacgg ggcttcaagc caggagatac tattttccac cggcagcaac 120

ggcgctgcac cgaacacggt ttacggtctg ttgctgtgtc ggggtgacat ttcccgtgcc 180

gcctgctatg actgtggaac ctctgtctgg cgtgacgccg gttccgcctg tcgtagagcg 240

aaagacgttg cgctggtcta taacgaatgt tatgctcgtc tgtctgataa agacgatttt 300

cttgctgata aagtcggtcc aggtcagctc accaccttga tgagttccac aaacatatcc 360

tctggagcgg acgtcgccgc atacgacaga gcggtaacaa ggctactggc agcgacagcc 420

gaatatgctg ctggagacat tgcgcggaaa ctgtttgcga ccggtcagcg cgttggcgca 480

gacccgggct tcccgaatct ctatgctact gcgcaatgcg cttttgatat cacccttgaa 540

gcatgccgcg gttgtctgga aggattggtg gctcgctggt gggatacctt ccccgcaaat 600

gtcgatggtg cacgtatagc cggtccgaga tgtttactac gtagcgaagt ttatcctttc 660

tataccgggg ctccgatggt ggtgctgcgc gaa 693

<210> 3

<211> 186

<212> DNA

<213> mice

<400> 3

atggatccga actgcagttg ttccaccggc ggttcctgca cctgtacgag ctcttgcgcc 60

tgtaaaaatt gcaaatgtac gagctgcaaa aaatcatgct gttcgtgctg tccggtgggc 120

tgctctaaat gtgcacaggg ctgcgtttgt aagggtgcgg ccgacaaatg tacctgctgt 180

gcttaa 186

Claims

1. An application of cadmium binding protein derived from rice (Oryza sativa) in reducing cadmium content in cadmium-contaminated soil, wherein the amino acid sequence of the cadmium binding protein is shown as SEQ ID No. 1.

2. Use according to claim 1, comprising: transforming the coding gene of the cadmium binding protein of claim 1 into a microbial strain to construct a recombinant engineering strain, and applying the recombinant engineering strain to cadmium-polluted soil.