JPH0532699A - Molecular weight marker - Google Patents

Abstract

PURPOSE:To obtain the title marker having exact molecular weight, easy to produce, for use in western blotting method etc., by plurally connecting either of IgG domains or several of these domains in protein A, G, or M. CONSTITUTION:With appropriate combination of genes coding protein A, G, or M and using manifestation vector and T4DNA ligase, recombinant plasmid is prepared by ligation reaction and then incorporated into Escherichia coli to make a transformation. The resulting product is incubated in a medium; the bacteria produced is collected, ground, agitated, extracted, and centrifuged. The resulting supernatant is taken, ammonium sulfate being added to the supernatant followed by separation of the resulting a 30-60% giving saturated ammonium sulfate precipitated fraction, thus the objective molecular weight marker protein with, as unit, either of IgG domains or several thereof in protein A, G, or M plurally connected.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a marker protein which can be widely used for Western blotting and various other purposes.

[0002] With the progress of biotechnology, the need for protein separation and identification has further increased, and various techniques have been developed. Among them, for example, SDS-
Polyacrylamide gel electrophoresis is commonly used for assaying protein purity and estimating its molecular weight. At that time, the molecular weight of the target protein is calculated on the basis of the mobility of the marker proteins simultaneously electrophoresed.
In the immunoblotting method using a specific antibody against the target protein, the target protein transferred onto the membrane is specifically stained even if other contaminant proteins are mixed. The marker protein is used as a molecular weight marker for the protein transcribed on such a membrane.

The present invention relates to a marker protein used as such a molecular weight marker. Therefore, the present invention plays an important role in the technical fields of protein engineering, biochemistry, genetic engineering and other biotechnology. is there.

[0004]

2. Description of the Related Art Several marker proteins have been known so far. For example, known molecular weight marker proteins for SDS-polyacrylamide gel electrophoresis include myosin (H chain), β-galactosidase, phosphorylase b, bovine. It is a mixture of proteins having appropriate molecular weights such as serum albumin, ovalbumin, carbonic anhydrase, soybean trypsin inhibitor and lysozyme. In Western blotting, the marker protein transferred onto the membrane is cleaved from the target protein lane and stained with a dye such as amide black.
In addition, there is a marker protein (a colored marker) which is made visible by the binding of an appropriate dye to these marker proteins, and these are directly transferred onto the membrane. Further, as a molecular weight marker for Western blotting, there is a marker that biotinizes the above protein and reacts with avidin-horseradish peroxidase (HRP) to develop a color (biotin labeled marker).

[0005]

The conventionally used marker protein is a mixture of various proteins, so that the staining properties and stability of each band vary.
Especially, there was a band that became thinner during storage. The mobility of the colored marker changes due to the binding of a dye, which is not suitable for accurate estimation of the molecular weight, and the band is generally broad. Biotin labeled marker is avidin-HR
It requires P and is not common.

In addition, the conventionally used marker proteins often lack the accuracy because the molecular weight is not constant, and the desired marker protein can be freely and efficiently designed by changing the molecular weight. I couldn't do anything.

[0007]

The present invention was made for the purpose of solving such problems, and as a result of investigations from various aspects, attention was paid to genetic engineering, and further research was conducted. As a result, we succeeded in freely amplifying these genes by PCR method (primer-based gene amplification method) using the parts of A and B in the IgG binding domain of protein A as one unit. For the first time, we succeeded in freely producing individual proteins.

The present invention has been completed as a result of further research based on the above-mentioned success, but industrially succeeded in efficiently producing IgG binding domains such as protein A, G, and M by genetic engineering. There are few examples, and in the current state of technology, the technology for increasing the number of domains as desired and freely producing a desired molecular weight has not been industrially established.

Hereinafter, the present invention will be described with respect to protein A, particularly AB domain and D domain thereof, but the same applies to other domains E and C, and protein G, its domains C ₁ , C ₂ and C _{3 are also described.} The same applies to the above, and also to other IgG-binding proteins such as protein M.

[0010]

[Example 1]

[0011]

[(1) Plasmid pTRP-PROT-ABI to VI
Construction of AB domain of protein A as a basic protein having the smallest molecular weight is planned, and the gene thereof is a commercially available protein A fusion protein expression vector pRI.
It was synthesized by PCR using T2T as a template (Fig. 2). At that time, a recognition sequence for the restriction enzyme AccI was introduced at both ends of the gene so that the gene was ligated in a certain direction. A
The recognition sequence of ccI is non-palindromic, and a DNA fragment having such a sequence at both ends is characterized in that it is ligated only in one direction. Other such restriction enzymes include AfLIII, AvaI, BanI, B
anII, HgiAI, etc.

The expression vector has a trp promoter and an AccI site as a cloning site, and for high expression in Escherichia coli, the amino acid next to the N-terminal amino acid Met is set to Lys, and its codon is set to AAA, so-called ATG vector. (PTRPACC) was prepared. The expression vector was inserted with one to six linked genes of the AB domain of protein A as a basic unit. PCR reaction is pRIT2
T was cleaved with HincII as a template, and as a sense primer, 5'-GGTAGACCGCTGATA
ACAATTTTCAACAAA-3 '(FIG. 3, PROT
S) as an antisense primer, 5'-GGT
CTACTTTTGGGTCTTGAGCATCATT
TA-3 ′ (FIG. 3, PPOTAS) and Taq polymerase (2.5 units) at 94 ° C. for 1 minute, 50
The target AB domain gene was amplified by carrying out 30 cycles of 1 minute at 72 ° C and 5 minutes at 72 ° C. A cloning site was also introduced into the expression vector using the same PCR reaction. The sense primer (ACCS) and antisense primer (ACCAS) used in this case are as shown in FIG.

The ligation reaction was carried out using T4 DNA ligase (350 units) at 14 ° C. for 16 hours.
Using this reaction product, E. coli JM109 (recA
l, endAl, gyrA96, thi, hsdR1
7, supE44, relAl, λ-, Δ (lac-p
roAB), [F ', traD36, proAB, la
cIq, lacZΔM15]) and then
L agar medium containing 0.7% of agar as recipient and 100 μg of ampicillin per ml (composition: 10 g of tryptone, 5 g of yeast extract, 10 g of salt per liter,
pH 7.4), and then overlaid on a plate of L agar medium containing agar 1.5% and ampicillin 100 μg / ml, cultured at 37 ° C. for one day, and plasmid DNA was separated by the alkali-SDS method. Agarose gel electrophoresis was performed to select a clone in which the target DNA fragment was inserted. In addition, the obtained plasmid D
By partially digesting NA with AccI, it was examined how many units of the protein A AB domain gene were inserted, and pT
RP-PROT-ABI to pTRP-PROT-AB
I named it VI.

[0014]

[(2) Transformed Escherichia coli JM109 / pTRP-PRO
Cultivation of T-ABI to VI] Plasmid pTRP-PR
E. coli JM109 transformed with OT-ABI to VI was cultured at 37 ° C. for 24 hours in an LB medium containing 100 μg of ampicillin per ml. The cells thus obtained were frozen and stored at -20 ° C.

[0015]

[(3) Crushing of bacteria and purification of each marker protein] After thawing the frozen bacterial cells at room temperature, the amount of 0.1
50 mM containing mM EDTA, 0.15 M NaCl
The cells were suspended in a phosphate buffer (pH 7.5), and the bacteria were crushed with Dynomill. 1/50 volume of 10% Lubr
After adding olPX and stirring at 0 ° C. for 15 minutes,
Centrifuge at 00 rpm for 20 minutes at 4 ° C., add ammonium sulfate to the centrifugation supernatant to make it 30% saturated, add ammonium sulfate to the centrifugation supernatant to make it 60% saturated, and centrifuge to precipitate a 30-60% saturated ammonium sulfate precipitate. Got a minute. Add a small amount of Buffer A (0.1 mM
It was dissolved in 50 mM phosphate buffer containing EDTA, pH 7.5), desalted with a Sephadex G-25 column, and then applied to a DEAE-Sepharose column equilibrated with the buffer A. The target protein is adsorbed on DEAE-Sepharose under this condition. After thoroughly washing the column with buffer A, 0-
Elution was performed with a linear concentration gradient of 1 M NaCl. The target protein was ELI using HRP-conjugated goat anti-rabbit IgG antibody.
Detected by SA. Target protein fraction 0.15M N
aCl, 0.05% Tween 20 in 50 mM Tris-hydrochloric acid buffer, which was applied to an IgG-Sepharose column equilibrated with pH 7.4, and the column was sufficiently washed with the same buffer, and then 0.5 M ammonium acetate buffer (pH 3.
It was eluted in 4). The eluted fraction was precipitated with 80% saturated ammonium sulfate, dissolved with a small amount of buffer A, and then TS equilibrated with 0.1 M phosphate buffer containing 0.2 M NaCl, pH 7.0.
High performance molecular sieve chromatography on a Kgel G3000SW column was performed. The fraction thus obtained showed a single band on SDS-polyacrylamide gel electrophoresis. Proteins showing the respective molecular weights were mixed in equal amounts to prepare a molecular weight marker for Western blotting. The molecular weight of each marker protein is shown in Table 1 below.
One AB domain consists of 116 amino acids and its molecular weight is 13205.24. Each marker protein has 4 amino acids of MetLysValAsp attached to the N-terminus and ThrGlyArgArgPheTh to the C-terminus.
Eight amino acids of rThrSer are attached. Also each AB
The domains are linked by 2 amino acids of ValAsp. Table 1 summarizes the number of AB domain linkages in each marker protein and their molecular weights.

[0016]

[Table 1]

The 6 kinds of molecular weight marker proteins thus prepared were subjected to SDS-polyacrylamide gel electrophoresis and the gel was stained with CBBR.
Got the result. In the figure, Lane M is a molecular weight marker manufactured by BRL, and Lanes 1 to 6 are PROT-ABI according to the present invention.
Although VI and lane 7 are a mixture of lanes 1 to 6, it is clearly recognized that lanes 1 to 7 have a desired predetermined molecular weight.

Similarly, each molecular weight marker protein was subjected to SDS-polyacrylamide gel electrophoresis as described above, and then electroblotted on a PVDF membrane, and rabbit serum was used as a primary antibody and horseradish peroxidase (HRP) was used as a secondary antibody. ) The bound goat anti-rabbit antibody was bound and the color was developed with the color-developing agent 4-chloro-1-naphthol, and the results in FIG. Each lane refers to the same as in Figure 4,
As is clear from FIG. 5, it was demonstrated that the molecular weight marker proteins (lanes 1 to 6) according to the present invention sufficiently function as a molecular weight marker. In addition, lanes 7, 8,
9, 10 are mixtures of lanes 1-6, lanes 9, 1
0 is dyed with Amido Black.

[0019]

Example 2 In the same manner as in Example 1, D of protein A was used.
Various marker proteins were prepared using the domain. The results are shown in Table 2 below. Table 2 summarizes the number of linkages when the D domain is a unit and the molecular weight of each marker protein.

[0020]

[Table 2]

As is clear from the above results, according to the present invention, marker proteins having various molecular weights can be freely prepared according to the purpose. Also Ig of protein A
In addition to A, B, and D described above, the G-binding domain also includes E and C.
(The amino acid sequence thereof is shown in FIG. 1), the target marker protein can be freely prepared between the same or different domains for E and C domains by the same method as described above. be able to.

[0022]

INDUSTRIAL APPLICABILITY The present invention is to produce a marker protein by utilizing a genetic engineering technique,
By selecting and binding each domain, it is possible to freely produce a marker protein having a target accurate molecular weight.

Therefore, the molecular weight marker for western blotting obtained by the present invention can be widely used not only in immunoblotting method but also as a general molecular weight marker in SDS-polyacrylamide gel electrophoresis method.

[Brief description of drawings]

FIG. 1 is a diagram comparing the amino acid sequences of five IgG-binding domains (E, D, A, B, C) of protein A, in which the portions that do not completely match among the five species are not common. Amino acids are underlined.

FIG. 2 is a construction diagram of an expression plasmid according to the present invention.

FIG. 3 shows two primers (PROTS, P) for amplifying the AB domain gene of protein A by PCR.
ROTAS) and the start codon and Ac in the expression vector
Two kinds of primers for introducing the cI site (ACC
S, ACCAS).

FIG. 4: SDS-PAGE of the molecular weight marker protein prepared according to the present invention, and the gel was subjected to CBBR.
It is the drawing dyed with.

FIG. 5: The molecular weight marker protein prepared according to the present invention was subjected to SDS-PAGE, and the gel was subjected to PVDF.
It is the figure which electro-blotted to the membrane and made the serum of a rabbit as a primary antibody and the HRP-conjugated goat anti-rabbit antibody as a secondary antibody couple | bonded, and was made to develop with 4-chloro- 1-naphthol. In FIGS. 4 and 5, each lane indicates the following: Lane M. BRL molecular weight marker;
1, PROT-ABI; 2, PROT-ABII; 3,
PROT-ABIII; 4, PROT-ABIV; 5,
PROT-ABV; 6, PROT-ABVI; 7,8,
9,10, mixture of lanes 2-7. P for CBBR staining
ROT-ABI, II is 1.0 μg, PROT-ABI
II-VI is 0.5 μg, PROT-ABI and II are 0.1 μg and P in Lane 1-7 of the blotted one.
ROT-ABIII-VI was 0.05 μg, lane 8,
In 9, PROT-ABI, II is 0.5 μg, PROT
-ABIII-VI is 0.25 μg, P in lane 10
ROT-ABI, II is 1.0 μg, PROT-ABI
II-VI used 0.5 microgram.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location (C12P 21/02 C12R 1:19)

Claims (7)

[Claims] 1. A marker protein comprising a plurality of IgG binding domains such as protein A, protein G or protein M, or some of them, which are linked to each other. . 2. The marker protein according to claim 1, wherein the IgG binding domain of protein A is E, D, A, B and / or C. 3. The IgG binding domain of protein G is C
_1. C ₁ , C ₂ and / or C ₃
Marker protein. 4. A marker protein comprising one or two or more IgG-binding domains of protein A or some of them as a unit. 5. When the marker protein is detected in Western blotting by the enzyme-antibody method using a specific antibody against the target protein in the Western blotting, the color is developed by the same operation without releasing the marker lane. Claims 1 to 4 characterized in that
The marker protein according to any one of 1. 6. The combination according to any one of claims 1 to 5, which is composed of a combination such that the difference in the molecular weight of each marker protein has a specific interval, and the proteins are of the same kind. Marker protein. 7. An IgG binding domain AB of protein A
Is a unit, and one or a plurality of these AB domains are linked to each other, which is a marker protein.