METHOD FOR FUSION EXPRESSION OF ION CHANNEL PROTEIN AND TRANSPORT PROTEIN AND PROTEIN FRAGMENT USED THEREFOR

Abstract

The present invention provides a protein fragment for fusion expression of ion channel protein and transport protein. The protein fragment is a Bril protein fragment or a T4L protein fragment. Also provided is a method for preparing a fusion protein by inserting a Brit protein fragment or T4L protein fragment into the N-terminal, C-terminal or intramembrane loop region of the ion channel protein and transport protein so as to improve its, in-vitro stability and crystallizability.

Claims

1. A protein fragment for fusion expression of ion channel protein and transport protein, characterized in that the protein fragment is a Bril protein fragment or a protein having a sequence homology of greater than 90% with this fragment, or a T4L protein fragment or a protein having a sequence homology of greater than 90% with this fragment.

2. The protein fragment for fusion expression of ion channel protein and transport protein according to claim 1, characterized in that said Bril protein fragment or the protein having a sequence homology of greater than 90% with this fragment has an amino acid sequence as set forth in SEQ ID NO.1.1 and a coding gene sequence as set forth in SEQ ID NO.2.1; and the said T4L protein fragment or the protein having a sequence homology of greater than 90% with this fragment has an amino acid sequence as set forth in SEQ ID NO.1.2 and a coding gene sequence as set forth in SEQ ID NO.2.2.

3. A method for fusion expression of ion channel protein and transport protein according to claim 1, characterized in that the amino acid sequence of the protein fragment as defined in claim 1 is inserted into the N-terminal, C-terminal or intramembrane loop region of the ion channel protein or transport protein to construct a fusion protein.

4. The method for fusion expression of ion channel protein and transport protein according to claim 3, characterized in that said Bril protein fragment and an ASIC1 are subjected to fusion expression to obtain a fusion protein having an amino acid sequence as set forth in SEQ ID NO.3.1; or said T4L protein fragment and an ASIC1 are subjected to fusion expression to obtain a fusion protein having an amino acid sequence as set forth in SEQ ID NO.3.2.

5. The method for fusion expression of ion channel protein and, transport protein according to claim 3, characterized in that an ASIC1 fusion expression plasmid constructed with the Bril gene has a gene sequence as set forth in SEQ ID NO.4.1; or an ASIC1 fusion expression plasmid constructed with the T4L gene has a gene sequence as set forth in SEQ ID NO.4.2.

6. The method for fusion expression of ion channel protein and transport protein according to claim 3, characterized in that said Bril protein fragment and a GLUT1 are subjected to fusion expression to obtain a fusion protein having an amino acid sequence as set forth in SEQ ID NO.3.3; or said T4L protein fragment and a GLUT1 are subjected to fusion expression to obtain a fusion protein having an amino acid sequence as set forth in SEQ ID NO.3.4.

7. The method for fusion expression of ion channel protein and transport protein according to claim 3, characterized in that a GLUT1 fusion expression plasmid constructed with the Bril gene has a gene sequence as set forth in SEQ ID NO.4.3; or a GLUT1 fusion expression plasmid constructed with the T4L, gene has a gene sequence as set forth in SEQ ID NO.4.4.

8. The fusion expression plasmid according to claim 5, characterized in that the fusion expression plasmid can be expressed in insect cells or can be expressed in mammalian cells.

9. The method for fusion expression of ion channel protein and transport protein according to claim 5, characterized in that the gene sequence as set forth in SEQ ID NO.4.1 or SEQ ID NO.4.2 described in claim 5 is constructed into an expression vector, such as pFastBac1, PcDNA3.1, PET21b and the like, for protein expression in different expression systems.

10. The method for fusion expression of ion channel protein and transport protein according to claim 7, characterized in that the gene sequence as set forth in SEQ ID NO.4.3 or SEQ ID NO.4.4 described in claim 7 is constructed into an expression vector, such as pFastBac1, PcDNA3.1, PET21b and the like, for protein expression in different expression systems.

11. The fusion expression plasmid according to claim 7, characterized in that the fusion expression plasmid can be expressed in insect cells or can be expressed in mammalian cells.

Description

DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 the electropherograms of the two purified ASIC1 fusion proteins, wherein the left spectrum is for the T4L-ASIC fusion protein, and the right spectrum is for the BRIL-ASIC1 fusion protein.

[0027] FIG. 2 the UPLC chromatograms of the two ASIC1 fusion proteins, wherein the left spectrum is for the T4L-ASIC fusion protein, and the right spectrum is for the BRIL-ASIC1 fusion protein.

[0028] FIG. 3 the electropherograms of the two purified GLUT1 fusion proteins, wherein the left spectrum is for the T4L-GLUT1 fusion protein, and the right spectrum is for the BRIL-GLUT1 fusion protein.

[0029] FIG. 4 the UPLC chromatograms of the two purified ASIC1 fusion proteins, wherein the left spectrum is for the T4L-GLUT1 fusion protein, and the right spectrum is for the BRIL-GLUT1 fusion protein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] A person skilled in the art will be able to construct a plasmid for fusion expression of ion channel protein or transport protein comprising a BRIL or T4L protein fragment by using methods well-known in the art, and these methods include in vitro recombination of DNA techniques, DNA synthesis techniques, in vivo recombination techniques. The constructed gene sequence for fusion expression of ion channel protein and transport protein can be effectively connected to an appropriate promoter of different expression vectors to guide the synthesis of mRNA.

[0031] The constructed plasmids can be transfected or transformed into cells by using conventional techniques well known to a person skilled in the art, for example, the PFastBac vector containing the fusion expression gene can be transformed into SF9 cells using the Bac-to-Bac technique for expression. Culture of the transformed cells and collection and passage of viruses, etc., are conventional techniques well known to a person skilled in the art.

EXAMPLE 1

Synthesis of Gene of ASIC1 (Acid-Sensing Ion Channel 1) Fusion Protein

[0032] Chemical synthesis

[0033] BRIL protein fragment (amino acid sequence as set forth in SEQ ID NO.1.1), nucleotide template (SEQ ID NO.2.1)

TABLE-US-00001 (5 GCTGATCTGGAAGACAATTGGGAAACTCTGAACGACAATCTCAAGG TGATCGAGAAGGCTGACAATGCTGCACAAGTCAAAGACGCTCTGACCAAG ATGAGGGCAGCAGCCCTGGACGCTCAGAAGGCCACTCCACCTAAGCTCGA GGACAAGAGCCCAGATAGCCCTGAAATGAAAGACTTTCGGCATGGATTCG ACATTCTGGTGGGACAGATTGATGATGCACTCAAGCTGGCCAATGAAGGG AAAGTCAAGGAAGCACAAGCAGCCGCTGAGCAGCTGAAGACCACCCGGAA TGCATACATTCAGAAGTACCTG3), theforwardprimerwas: (5 CCCACCATCGGGCGCGGATCCATGCATCACCATCATCACCACCATC ACGCTGATCTGGAAGACAATTGG3), thereverseprimerwas: (5 CCCCTGAAAGTACAGGTTTTCCAGGTACTTCTGAATGTATGC 3),
the gene of BRIL protein fragment was obtained by means of PCR reaction.

[0034] The ASIC1 nucleotide template was chemically synthesized with reference to human gene codons,

TABLE-US-00002 (5 ATGGAACTGAAGGCCGAGGAGGAGGAGGTGGGTGGCGTCCAGCCGG TGAGCATCCAGGCCTTCGCCAGCAGCTCCACACTGCACGGCCTGGCCCAC ATCTTCTCCTACGAGCGCCTGTCTCTGAAGCGCGCACTGTGGGCCCTGTG CTTCCTGGGCTCCCTGGCTGTGCTGCTGTGTGTGTGCACGGAGCGCGTGC AGTACTACTTCCACTACCACCATGTCACCAAGCTCGACGAGGTGGCTGCC TCTCAGCTTACCTTCCCTGCTGTCACGCTGTGCAACCTCAACGAGTTCCG CTTTAGCCAAGTCTCCAAGAATGACCTGTATCATGCTGGCGAGCTGCTGG CCCTGCTCAACAACAGGTATGAGATACCAGACACACAGATGGCAGATGAA AAGCAGCTGGAGATACTGCAGGACAAAGCCAACTTCCGCAGCTTCAAACC CAAACCCTTCAACATGCGCGAGTTCTACGACCGCGCTGGCCACGACATTC GCGACATGCTGCTCTCCTGCCACTTCCGCGGCGAGGTCTGCAGCGCTGAA GACTTCAAGGTGGTCTTCACACGCTATGGAAAGTGCTACACGTTCAACTC CGGCCGCGATGGCCGCCCGCGCCTGAAGACCATGAAGGGTGGCACGGGCA ATGGCCTGGAAATCATGCTGGACATCCAGCAGGACGAGTACCTGCCTGTG TGGGGCGAGACTGACGAGACGTCCTTCGAAGCAGGCATCAAAGTGCAGAT CCATAGTCAGGATGAACCTCCTTTCATCGACCAGCTGGGCTTTGGCGTGG CCCCAGGCTTCCAGACCTTTGTGGCCTGCCAGGAGCAGCGCCTCATCTAC CTGCCCCCACCCTGGGGCACCTGCAAAGCTGTTACCATGGACTCCGATTT GGATTTCTTCGACTCCTACAGCATCACTGCCTGCCGCATCGACTGTGAGA CGCGCTACCTGGTGGAGAACTGCAACTGCCGCATGGTGCACATGCCAGGC GATGCCCCATACTGTACTCCAGAGCAGTACAAGGAGTGTGCAGATCCTGC TCTGGACTTCCTGGTGGAAAAGGACCAGGAGTACTGCGTGTGTGAAATGC CTTGCAACCTGACCCGCTATGGCAAAGAGCTGTCCATGGTCAAGATCCCC AGCAAAGCCTCAGCCAAGTACCTGGCCAAGAAGTTCAACAAATCTGAGCA ATACATAGGCGAGAACATCCTGGTGCTGGACATAACTTTGAAGTCCTCAA CTATGAGACCATTGAACAGAAGAAGGCCTATGAGATTGCAGGCCTCCTGG GTGACATCGGCGGCCAGATGGGCCTGTTCATCGGCGCCAGCATCCTCACG GTGCTGGAGCTCTTTGACTACGCCTACGAGGTCATTAAGCACAAGCTGTG CCGCCGCGGAAAATGCCAGAAGGAGGCCAAAAGGAGCAGTGCGGACAAGG GCGTGGCCCTCAGCCTGGACGACGTCAAAAGACACAACCCGTGCGAGAGC CTTCGCGGCCACCCTGCCGGCATGACATACGCTGCCAACATCCTGCCTCA CCATCCGGCCCGCGGCACGTTCGAGGACTTTACCTGCTGA3), theforwardprimerwas (5 GAAAACCTGTACTTTCAGGGGTCCACACTGCACGGCCTGGCCCACA 3), thereverseprimerwas (5 CTTGGTACCGCATGCCTCGAGTTACTTGTGCTTAATGACCTCGTAG 3),
and the gene ASIC1 (25-464) was obtained by PCR reaction. The forward primer was (5CCCACCATCGGGCGCGGATCCATGCATCACCATCATCACCACCATCACGA AAACCTGTACTTTCAG 3) the reverse primer was (5CTTGGTACCGCATGCCTCGAGTTACTTGTGCTTAATGACCTCGTAG 3), and the gene 8*His-BRIL(23-128)-TEV-ASIC1(26-464) was obtained by PCR reaction. The gene synthesis was carried out according to the above principle, the forward primer was introduced into the restriction enzyme cleavage site BamHI, and the reverse primer was introduced into the restriction enzyme cleavage site XhoI and the stop codon.

[0035] The T4L protein (amino acid sequence as set forth in SEQ ID NO.1.2 in the sequence listing) and nucleotide template thereof having a sequence as set forth in SEQ ID NO.2.2 in the sequence listing

TABLE-US-00003 (5 AACATCTTCGAGATGCTCCGTATCGACGAGGGCCTCAGGTTGAAGA TCTATAAGGACACAGAGGGCTATTACACCATCGGTATTGGTCATCTCTTG ACTAAGTCGCCTTCACTTAACGCAGCAAAATCCGAACTGGACAAGGCCAT CGGTCGCAATACAAATGGTGTCATTACTAAGGACGAAGCTGAAAAGCTCT TCAACCAGGACGTTGATGCAGCTGTTCGCGGAATCCTGCGCAACGCAAAG CTCAAGCCGGTTTACGATTCTTTGGACGCCGTTCGCCGTGCGGCCTTGAT TAACATGGTGTTTCAGATGGGTGAAACCGGAGTTGCAGGATTTACCAACT CGCTGAGGATGCTGCAACAAAAGAGATGGGACGAAGCCGCTGTGAATCTC GCCAAATCTAGGTGGTACAACCAGACACCCAATCGTGCGAAGAGAGTGAT AACTACATTCCGCACCGGTACTTGGGACGCATAT3), theforwardprimerwas: (5 CCCACCATCGGGCGCGGATCCATGCATCACCATCATCACCACCATC ACAACATCTTCGAGATGCTCCGT3), thereverseprimerwas: (5 CCCCTGAAAGTACAGGTTTTCATATGCGTCCGTACCGGTG3),
and the gene of the T4L protein fragment was obtained by means of PCR reaction.

[0036] The ASIC1 nucleotide template was chemically synthesized with reference to human gene codons,

TABLE-US-00004 (5 ATGGAACTGAAGGCCGAGGAGGAGGAGGTGGGTGGCGTCCAGCCGG TGAGCATCCAGGCCTTCGCCAGCAGCTCCACACTGCACGGCCTGGCCCAC ATCTTCTCCTACGAGCGCCTGTCTCTGAAGCGCGCACTGTGGGCCCTGTG CTTCCTGGGCTCCCTGGCTGTGCTGCTGTGTGTGTGCACGGAGCGCGTGC AGTACTACTTCCACTACCACCATGTCACCAAGCTCGACGAGGTGGCTGCC TCTCAGCTTACCTTCCCTGCTGTCACGCTGTGCAACCTCAACGAGTTCCG CTTTAGCCAAGTCTCCAAGAATGACCTGTATCATGCTGGCGAGCTGCTGG CCCTGCTCAACAACAGGTATGAGATACCAGACACACAGATGGCAGATGAA AAGCAGCTGGAGATACTGCAGGACAAAGCCAACTTCCGCAGCTTCAAACC CAAACCCTTCAACATGCGCGAGTTCTACGACCGCGCTGGCCACGACATTC GCGACATGCTGCTCTCCTGCCACTTCCGCGGCGAGGTCTGCAGCGCTGAA GACTTCAAGGTGGTCTTCACACGCTATGGAAAGTGCTACACGTTCAACTC CGGCCGCGATGGCCGCCCGCGCCTGAAGACCATGAAGGGTGGCACGGGCA ATGGCCTGGAAATCATGCTGGACATCCAGCAGGACGAGTACCTGCCTGTG TGGGGCGAGACTGACGAGACGTCCTTCGAAGCAGGCATCAAAGTGCAGAT CCATAGTCAGGATGAACCTCCTTTCATCGACCAGCTGGGCTTTGGCGTGG CCCCAGGCTTCCAGACCTTTGTGGCCTGCCAGGAGCAGCGCCTCATCTAC CTGCCCCCACCCTGGGGCACCTGCAAAGCTGTTACCATGGACTCCGATTT GGATTTCTTCGACTCCTACAGCATCACTGCCTGCCGCATCGACTGTGAGA CGCGCTACCTGGTGGAGAACTGCAACTGCCGCATGGTGCACATGCCAGGC GATGCCCCATACTGTACTCCAGAGCAGTACAAGGAGTGTGCAGATCCTGC TCTGGACTTCCTGGTGGAAAAGGACCAGGAGTACTGCGTGTGTGAAATGC CTTGCAACCTGACCCGCTATGGCAAAGAGCTGTCCATGGTCAAGATCCCC AGCAAAGCCTCAGCCAAGTACCTGGCCAAGAAGTTCAACAAATCTGAGCA ATACATAGGCGAGAACATCCTGGTGCTGGACATTTTCTTTGAAGTCCTCA ACTATGAGACCATTGAACAGAAGAAGGCCTATGAGATTGCAGGCCTCCTG GGTGACATCGGCGGCCAGATGGGCCTGTTCATCGGCGCCAGCATCCTCAC GGTGCTGGAGCTCTTTGACTACGCCTACGAGGTCATTAAGCACAAGCTGT GCCGCCGCGGAAAATGCCAGAAGGAGGCCAAAAGGAGCAGTGCGGACAAG GGCGTGGCCCTCAGCCTGGACGACGTCAAAAGACACAACCCGTGCGAGAG CCTTCGCGGCCACCCTGCCGGCATGACATACGCTGCCAACATCCTGCCTC ACCATCCGGCCCGCGGCACGTTCGAGGACTTTACCTGCTGA3), theforwardprimerwas (5 GAAACCTGTTACTTTCAGGGGTCCACACTGCACGGCCTGGCCCACA 3), thereverseprimerwas (5 CTTGGTACCGCATGCCTCGAGTTACTTGTGCTTAATGACCTCGTAG 3),
and the gene ASIC1 (25-464) was obtained by PCR reaction. The forward primer was (5CCCACCATCGGGCGCGGATCCATGCATCACCATCATCACCACCATCACGA AAACCTGTACTTTCAG 3), the reverse primer was (5CTTGGTACCGCATGCCTCGAGTTACTTGTGCTTAATGACCTCGTAG 3), and the gene 8*His-T4L(2-161)-TEV-ASIC1(25-464) was obtained by PCR reaction. The gene was synthesized according to the above principle, the forward primer was introduced into the restriction enzyme cleverage site BamHI, and the reverse primer was introduced into the restriction enzyme cleverage site XhoI and the stop codon.

[0037] The PCR reaction conditions were as lows: 0.2 M of an amplification primer was added to a 50 L of reaction system (PCR Buffer, 1.5 mM MgSO.sub.4, 200 M dNTPs), and PCR cycle was started after a thorough mixing: denaturation at 94 C. for 5 minutes, denaturation at 94 C. for 30 seconds, annealing at 55 C. for 30 seconds, and elongation at 68 C. for 2 minutes; total 30 cycles were carried out, and finally the temperature was kept at 68 C. for 10 minutes. The PCR products were identified by 1.2% agarose gel electrophoresis, and recovered for cloning.

EXAMPLE 2

Construction of Plasmid for an ASIC1 (Acid-Sensing Ion Channel 1) Fusion Protein

[0038] The PCR fragment obtained in Example 1 was ligated with the vector pFastBac1 (purchased from Invitrogen) double-cleaved with the two restriction enzymes EcoRI and XhoI. The ligated product was transformed into the competent E. coli (Escherichia coli) DH5 and the volume thereof should not exceed 10% of the competent cells. The contents were homogenously mixed by gently rotating for several times, the tubes with contents were cooled in an ice bath for 30 minutes, and the tubes were placed in a 42 C. water bath and subjected to thermal shock for 60 seconds. The tubes were quickly transferred to an ice bath and stood for 120 seconds so as to cool the cells. 400 l of LB culture medium was added to each tube and and the tube was incubated at 37 C. for 60 minutes under slowly shaking so that the bacteria were resuscitated to express a plasmid-encoded antibiotic resistance marker gene was expressed, and centrifuged at low speed for 2 minutes. The supernatant was removed, leaving about 100 l of culture medium in the centrifuge tube, and re-suspending bacteria, and the solution of bacteria was homogenously spread with a glass spatula on an agar plate. The plate was inverted in a constant temperature incubator at 37 C., and colonies might emerge after 12-16 hours. The positive clones were picked and identified after application on the plate.

EXAMPLE 3

Expression of the ASIC1 (Acid-Sensing Ion Channel 1) Fusion Protein

[0039] The recombinant plasmid obtained in Example 2 was transformed into DH10Bac E. coli competent cells, and the volume thereof should not exceed 5% of the competent cells. The contents were homogenously mixed by gently rotating, for several times. The tubes with contents were cooled in an ice bath for 30 minutes, and the tubes were placed in a 42 C. water bath and subjected to thermal shock for 90 seconds. The tubes were quickly transferred, to an ice bath and stood for 120 seconds so as to cool the cells. 800 l of LB culture medium was added to each tube and the tube was incubated at 37 C. for 4 hours under slowly shaking so that the bacteria were resuscitated to express a plasmid-encoded antibiotic resistance marker gene. 30 l of the solution of bacteria was homogenously spread with a glass spatula on an agar plate. The plate was inverted in a constant temperature incubator at 37 C., and positive blue and white spot colonies emerged after 30-48 hours, The positive white spot colonies were picked into 5 ml of resistant LB, and incubated for 12-16 hours under slowly shaking, and the bacteria were identified by PCR. The results showed that bacmid recombination was correct. The recombinant bacmid was transfected into insect cells with a transfection reagent. After 4-5 days, the cell supernatant was collected as the first generation baculovirus. The second generation virus for expressing the fusion polypeptide was obtained after 72 hours of infection of the insect cells with the first generation baculovirus. The insect cells sf9 with a density of 210.sup.6/ml were infected by the second generation virus at a volume ratio of 1:100. After 72 hours of further incubation, cells were harvested by centrifugation and washed with PBS for once.

EXAMPLE 4

Purification of the ASIC1 (Acid-Sensing Ion Channel 1) Fusion Protein

[0040] 1 L of cells were re-suspended in 100 ml of a precooled lysate (25 mM Tris pH 8.0 10 mM MgCl.sub.2, 20 mM KCl), homogenized on ice using a homogenizer, and centrifuged with an ultracentrifuge for 45 minutes after homogenization; the supernatant was removed; the washing step was repeated for three times, and then the washing step was repeated with a high-salt solution for three times. The extracted cell membrane was dissolved with a lysis solution containing glycerol, quickly frozen with liquid nitrogen, and stored in a 80 C. refrigerator, The cell membrane was thawed and defrosted on ice. After 30 minutes, a buffer for dissolving membranes was added to the cell me b in an amount of 100 ml per 1 L of the cell membrane, and then the dissolved membranes were placed on ice overnight, and centrifuged in, an ultracentrifuge at 100,000 g of of centrifugal force for 1 hour. The precipitate was removed, and the supernatant was then incubated overnight with 1 mL of Talon IMAC resin balanced with a balance buffer. In the next day, the supernatant was removed, and an appropriate amount of balance buffer was added to re-suspend packing. The packing was transferred to a gravity column, and washed with 10 column volumes of a rinse buffer 1 (25 mM Tris pH8.0; 150 mM NaCl, 0.05% DDM; 5 mM MgCl.sub.2), 10 column volumes of a rinse buffer 2 (25 mM Tris pH8.0; 150 mM NaCl, 0.05% DDM; 5 mM MgCl.sub.2; 25 mM Imid), and 5 column volumes of a rinse buffer 3 (25 mM Tris pH8.0; 150 mM NaCl; 0.05% DDM; 5 mM MgCl; 50 mM Imid), and then the proteins of interest were eluted with 5 column volumes of elution buffer (25 mM Tris pH8.0; 150 mM NaCl; 0.05% DDM; 5 mM MgCl.sub.2; 250 mM Imid). The purified proteins of interest were stored at 80 C. The results of electrophoresis of the three fusion proteins were shown in FIG. 1.

[0041] As viewed from yield, the yield of the three purified membrane proteins exceeded 1 mg/L cells, suggesting a high yield.

EXAMPLE 5

Detection of Homogeneity of the Inventive ASIC1 (Acid-Sensing Ion Channel 1) Fusion Protein

[0042] The detection was carried out by using Acquity H-Class Bio UPLC system from Wasters Company, wherein the column used in the detection was a Sepax EC250 molecular sieve column. Prior to sample application, the column was washed with a balance buffer (25 mM Tris pH 5.0; 150 mM NaCl; 0.05% DDM; 5 mM MgCl.sub.2) until the baseline was not much changed, and then a sample to be detected was added into a special 96-hole plate. The integration treatment was performed by softwares of the instrument per se.

[0043] The three fusion proteins were detected according to the above-described method and the results were shown in FIG. 2. The results showed that the three fusion proteins have good homogeneity, a monomer peak of the fusion proteins is detectable, and the monomer accounts for a majority of the protein sample.

EXAMPLE 6

Synthesis of Gene of GLUT1 (Glucose Transporter) Fusion Protein

[0044] The T4L protein (amino acid sequence as set forth in SEQ ID NO.1.2 in the sequence listing) and nucleotide template thereof having a sequence as set forth in SEQ ID NO.2.2 in the sequence listing

TABLE-US-00005 (5 AACATCTTCGAGATGCTCCGTATCGACGAGGGCCTCAGGTTGAAGA TCTATAAGGACACAGAGGGCTATTACACCATCGGTATTGGTCATCTCTTG ACTAAGTCGCCTTCACTTAACGCAGCAAAATCCGAACTGGACAAGGCCAT CGGTCGCAATACAAATGGTGTCATTACTAAGGACGAAGCTGAAAAGCTCT TCAACCAGGACGTTGATGCAGCTGTTCGCGGAATCCTGCGCAACGCAAAG CTCAAGCCGGTTTACGATTCTTTGGACGCCGTTCGCCGTGCGGCCTTGAT TAACATGGTGTTTCAGATGGGTGAAACCGGAGTTGCAGGATTTACCAACT CGCTGAGGATGCTGCAACAAAAGAGATGGGACGAAGCCGCTGTGAATCTC GCCAAATCTAGGTGGTACAACCAGACACCCAATCGTGCGAAGAGAGTGAT AACTACATTCCGCACCGGTACTTGGGACGCATAT3), theforwardprimerwas: (5 CCCGTTTCTGCTAGCAAGCTTACATGATCTCGAGATGCTCCGTATC 3), thereverseprimerwas: (5 CAGCTTCTTGCTGCTGGGCTCCATATATGGTCCCAAGTACCGGTGC 3),
and the gene of the T4L protein fragment was obtained by PCR reaction.

[0045] The GLUT1 nucleotide template was chemically synthesized with reference to human gene codons.

TABLE-US-00006 (5 ATGGAGCCCAGCAGCAAGAAGCTGACGGGTCGCCTCATGCTGGCCG TGGGAGGAGCAGTGCTTGGCTCCCTGCAGTTTGGCTACAACACTGGAGTC ATCAATGCCCCCCAGAAGGTGATCGAGGAGTTCTACAACCAGACATGGGT CCACCGCTATGGGGAGAGCATCCTGCCCACCACGCTCACCACGCTCTGGT CCCTCTCAGTGGCCATCTTTCTGTTGGGGGCATGATTGGCTCCTTCTCTG TGGGCCTTTTCGTTAACCGCTTTGGCCGGCGGAATTCAATGCTGATGATG AACCTGCTGGCCTTCGTGTCCGCCGTGCTCATGGGCTTCTCGAAACTGGG CAAGTCCTTTGAGATGCTGATCCTGGGCCGCTTCATCATCGGTGTGTACT GCGGCCTGACCACAGGCTTCGTGCCCATGTATGTGGGTGAAGTGTCACCC ACAGCCCTTCGTGGGGCCCTGGGCACCCTGCACCAGCTGGGCATCGTCGT CGGCATCCTCATCGCCCAGGTGTTCGGCCTGGACTCCATCATGGGCAACA AGGACCTGTGGCCCCTGCTGCTGAGCATCATCTTCATCCCGGCCCTGCTG CAGTGCATCGTGCTGCCCTTCTGCCCCGAGAGTCCCCGCTTCCTGCTCAT CAACCGCAACGAGGAGAACCGGGCCAAGAGTGTGCTAAAGAAGCTGCGCG GGACAGCTGACGTGACCCATGACCTGCAGGAGATGAAGGAAGAGAGTCGG CAGATGATGCGGGAGAAGAAGGTCACCATCCTGGAGCTGTTCCGCTCCCC CGCCTACCGCCAGCCCATCCTCATCGCTGTGGTGCTGCAGCTGTCCCAGC AGCTGTCTGGCATCAACGCTGTCTTCTATTACTCCACGAGCATCTTCGAG AAGGCGGGGGTGCAGCAGCCTGTGTATGCCACCATTGGCTCCGGTATCGT CAACACGGCCTTCACTGTCGTGTCGCTGTTTGTGGTGGAGCGAGCAGGCC GGCGGACCCTGCACCTCATAGGCCTCGCTGGCATGGCGGGTTGTGCCATA CTCATGACCATCGCGCTAGCACTGCTGGAGCAGCTACCCTGGATGTCCTA TCTGAGCATCGTGGCCATCTTTGGCTTTGTGGCCTTCTTTGAAGTGGGTC CTGGCCCCATCCCATGGTTCATCGTGGCTGAACTCTTCAGCCAGGGTCCA CGTCCAGCTGCCATTGCCGTTGCAGGCTTCTCCAACTGGACCTCAAATTT CATTGTGGGCATGTGCTTCCAGTATGTGGAGCAACTGTGTGGTCCCTACG TCTTCATCATCTTCACTGTGCTCCTGGTTCTGTTCTTCATCTTCACCTAC TTCAAAGTTCCTGAGACTAAAGGCCGGACCTTCGATGAGATCGCTTCCGG CTTCCGGCAGGGGGGAGCCAGCCAAAGTGACAAGACACCCGAGGAGCTGT TCCATCCCCTGGGGGCTGATTCCCAAGTGTGA3), theforwardprimerwas (5 ATGGAGCCCAGCAGCAAGAAGCTG3), thereverseprimerwas (5 ATGATGGTGGTGATGGTGGTGATGGTGGTGTGTCTTGTCACTTTGG CTGGCTC3),
and the gene GLUT1(1-478) was obtained by PCR reaction. The forward primer was (5CCCGTTTCTGCTAGCAAGCTTACCATGAACATCTTCGAGATGCTCCGTATC 3), the reverse primer was (5GGTCGAGGTCGGGGGATCCTTAATGATGGTGGTGATGGTGGTGATG 3), and the gene T4L-GLUT1(1-478)-10*His was obtained by means of PCR reaction. The gene was synthesized according to the above principle, the forward primer was introduced into the restriction enzyme cleverage site HindIII, and the reverse primer was introduced into the restriction enzyme cleverage site BamHI and the stop codon.

[0046] BRIL protein fragment (amino acid sequence as set forth in SEQ ID NO.1.1), nucleotide template (SEQ ID NO.2.1)

TABLE-US-00007 5 GCTGATCTGGAAGACAATTGGGAAACTCTGAACGACAATCTCAAGGT GATCGAGAAGGCTGACAATGCTGCACAAGTCAAAGACGCTCTGACCAAGA TGAGGGCAGCAGCCCTGGACGCTCAGAAGGCCACTCCACCTAAGCTCGAG GACAAGAGCCCAGATAGCCCTGAAATGAAAGACTTTCGGCATGGATTCGA CATTCTGGTGGGACAGATTGATGATGCACTCAAGCTGGCCAATGAAGGGA AAGTCAAGGAAGCACAAGCAGCCGCTGAGCAGCTGAAGACCACCCGGAAT GCATACATTCAGAAGTACCTG3), theforwardprimerwas: (5 GCTGATCTGGAAGACAATTGGGAAAC3), thereverseprimerwas: (5 CAGGTACTTCTGAATGTATGCATTC),
and the gene of the BRIL protein fragment was obtained by means of PCR reaction.

[0047] The GLUT1 nucleotide template was chemically synthesized with reference to human gene codons,

TABLE-US-00008 (5 ATGGAGCCCAGCAGCAAGAAGCTGACGGGTCGCCTCATGCTGGCCG TGGGAGGAGCAGTGCTTGGCTCCCTGCAGTTTGGCTACAACACTGGAGTC ATCAATGCCCCCCAGAAGGTGATCGAGGAGTTCTACAACCAGACATGGGT CCACCGCTATGGGGAGAGCATCCTGCCCACCACGCTCACCACGCTCTGGT CCCTCTCAGTGGCCATCTTTCTGTTGGGGGCATGATTGGCTCCTTCTCTG TGGGCCTTTTCGTTAACCGCTTTGGCCGGCGGAATTCAATGCTGATGATG AACCTGCTGGCCTTCGTGTCCGCCGTGCTCATGGGCTTCTCGAAACTGGG CAAGTCCTTTGAGATGCTGATCCTGGGCCGCTTCATCATCGGTGTGTACT GCGGCCTGACCACAGGCTTCGTGCCCATGTATGTGGGTGAAGTGTCACCC ACAGCCCTTCGTGGGGCCCTGGGCACCCTGCACCAGCTGGGCATCGTCGT CGGCATCCTCATCGCCCAGGTGTTCGGCCTGGACTCCATCATGGGCAACA AGGACCTGTGGCCCCTGCTGCTGAGCATCATCTTCATCCCGGCCCTGCTG CAGTGCATCGTGCTGCCCTTCTGCCCCGAGAGTCCCCGCTTCCTGCTCAT CAACCGCAACGAGGAGAACCGGGCCAAGAGTGTGCTAAAGAAGCTGCGCG GGACAGCTGACGTGACCCATGACCTGCAGGAGATGAAGGAAGAGAGTCGG CAGATGATGCGGGAGAAGAAGGTCACCATCCTGGAGCTGTTCCGCTCCCC CGCCTACCGCCAGCCCATCCTCATCGCTGTGGTGCTGCAGCTGTCCCAGC AGCTGTCTGGCATCAACGCTGTCTTCTATTACTCCACGAGCATCTTCGAG AAGGCGGGGGTGCAGCAGCCTGTGTATGCCACCATTGGCTCCGGTATCGT CAACACGGCCTTCACTGTCGTGTCGCTGTTTGTGGTGGAGCGAGCAGGCC GGCGGACCCTGCACCTCATAGGCCTCGCTGGCATGGCGGGTTGTGCCATA CTCATGACCATCGCGCTAGCACTGCTGGAGCAGCTACCCTGGATGTCCTA TCTGAGCATCGTGGCCATCTTTGGCTTTGTGGCCTTCTTTGAAGTGGGTC CTGGCCCCATCCCATGGTTCATCGTGGCTGAACTCTTCAGCCAGGGTCCA CGTCCAGCTGCCATTGCCGTTGCAGGCTTCTCCAACTGGACCTCAAATTT CATTGTGGGCATGTGCTTCCAGTATGTGGAGCAACTGTGTGGTCCCTACG TCTTCATCATCTTCACTGTGCTCCTGGTTCTGTTCTTCATCTTCACCTAC TTCAAAGTTCCTGAGACTAAAGGCCGGACCTTCGATGAGATCGCTTCCGG CTTCCGGCAGGGGGGAGCCAGCCAAAGTGACAAGACACCCGAGGAGCTGT TCCATCCCCTGGGGGCTGATTCCCAAGTGTGA3), theforwardprimerwas (5 CCCGTTCTGCTAGCAAGCTTACCATGGAGCCCAGCAGCAAGAAGCT G3), thereverseprimerwas (5 GTTTCCCAATTGTCTTCCAGATCAGCCTTGGCCCGGTTCTCCTCGT TG3)
and the gene GLUT1(1-225) was obtained by PCR reaction; the forward primer was (5GAATGCATACATTCAGAAGTACCTGGAGAAGAAGGTCACCATCCTGGAGC 3), the reverse primer was (5ATGATGGTGGTGATGGTGGTGATGGTGGTGCACTTGGGAATCAGGCCCC A 3), and the gene GLUT1(254-492) was obtained by PCR reaction. The forward primer was (5CCCGTTTCTGCTAGCAAGCTTACCATGGAGCCCAGCAGCAAGAAGCTG 3), the reverse primer was (5GGTCGAGGTCGGGGGATCCTTAATGATGGTGGTGATGGTGGIGATG and the gene GLUT1(1-225)-BRIL(130-233)-TEV-GLUT1(254-492)-10*His was obtained by PCR reaction. The gene was synthesized according to the above principle, the forward primer was introduced into the restriction enzyme cleverage site Hind III, and the reverse primer was introduced into the restriction enzyme cleverage site BamHI and the stop codon.

EXAMPLE 7

Expression of the Inventive GLUT1 (Glucose Transporter) Fusion Protein

[0048] 1 mg of the GLUT1 plasmid in Example 6 was dissolved in 50 ml of Opti-MEM culture medium and homogenously mixed, then further dissolved with 3 ml of PEI (1 mg/ml) in 50 Opti-MEM culture medium and mixed homogenously, incubated at room temperature for 15 minutes, added to 1 L of 293F cells with a cell density of 1.210.sup.6 cells/ml, and cultured at 37 C. in 5% CO.sub.2 for 72 hours, and the cell precipitates were collected.

EXAMPLE 8

Purification of the Inventive GLUT1 (Glucose Transporter) Fusion Protein

[0049] 300 mL of cells were re-suspended in 20 ml of a precooled lysate (50 mM Tris pH7.5, 200 mM NaCl, 5% glycerol), homogenized on ice using a homogenizer, and centrifuged with an ultracentrifuge for 50 minutes after homogenization; the supernatant was removed; the washing step was repeated for three times, and then the washing step was repeated with a high-salt solution (50 mM Tris pH7.5, 1M NaCl, 5% glycerol) for twice. A buffer for dissolving membranes (50 mM Tris pH7.5, 200 mM NaCl, 5% glycerol, 1% DDM) was added to the extracted cell membrane in an amount of 20 ml per 300 mL of cells, homogenized on ice using a homogenizer, the dissolved membranes were stirred using a magnetic stirring apparatus at 4 C. overnight, and centrifuged in an ultracentrifuge at 100,000 g of centrifugal force for 1 hour. The precipitate was removed, and the supernatant was then incubated with 1 mL of Talon IMAC resin balanced with a balance buffer (50 Mm Tris pH7.5, 200 mM NaCl, 5% glycerol, 0.05% DDM) for 3 hours. The supernatant was removed, and an appropriate amount of balance buffer was added to re-suspend packing. The packing was transferred to a gravity column, arid washed with 10 column volumes of a rinse buffer 1 (250 mil Tris pH7.5, 200 nM NaCl, 5% glycerol, 0.05% DDM), 1 column volumes of a rinse buffer 2 (50 mM Tris pH7.5, 200 mM NaCl, 5% glycerol, 0.05% DDM, 20 mM imidazole), and 5 column volumes of a rinse buffer 3 (50 mM Tris pH7.5, 200 mM NaCl, 5% glycerol, 0.05% DDM, 50 mM imidazole), and then the proteins of interest were eluted with 5 column volumes of elution buffer (50 mM Tris pH7.5, 200 mM NaCl, 5% glycerol, 0.05% DDM, 250 mM imidazole). The purified proteins of interest were concentrated to 400 L and stored at 80 C. The results of electrophoresis of the three fusion proteins were shown in FIG. 3.

[0050] As viewed from yield, the yield of the two purified GLUT1 fusion proteins exceeded 0.5 mg/L cells, suggesting a high yield.

EXAMPLE 9

Detection of Homogeneity of the Inventive GLUT1 (Glucose Transporter) Fusion Protein

[0051] The detection was carried out by using Acquity H-Class Bio UPLC system from Wasters Company, wherein the column used in the assay was a Sepax SEC250 molecular sieve column.sub. Prior to sample application, the column was washed with a balance buffer (25 mM Tris pH 8.0; 150 mM NaCl; 0.05% DDM; 5 mM MgCl.sub.2) until the baseline was not much changed, and then a sample to detected was added into a special 96-hole plate. The integration treatment was performed by softwares of the instrument per se.

[0052] The three fusion proteins were detected according to the above-described method, and the results were shown in FIG. 4. The results showed that the two GLUT1 fusion proteins have good homogeneity, a monomer peak of the fusion proteins is detectable, and the monomer accounts for a majority of the protein sample.