# US 8,541,005 B2 · Cysteine-tagged streptococcal protein G variant > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,541,005 B2 - Document ID: US8541005B2 - Status: Granted - Kind: B2 - Application number: 12/306,903 - Filed: 2007-06-20 - Published: 2010-07-08 - Granted: 2013-09-24 - Earliest claimed: 2006-06-27 - Assignees: Korea Research Institute of Bioscience and Biotechnology - Applicants: Bong Hyun Chung; Jeong Min Lee; Sun-Ok Jung; Yongwon Jung - Inventors: Bong Hyun Chung; Jeong Min Lee; Sun-Ok Jung; Yongwon Jung - Web page: https://patentgrep.com/patent/US8541005B2 ## CPC - C07K 14/31: from Staphylococcus (G) - C07K 17/00: Carrier-bound or immobilised peptides (carrier-bound or immobilised enzymes C12N11/00); Preparation thereof - G01N 33/54366: {Apparatus specially adapted for solid-phase testing} - G01N 33/54393: {Improving reaction conditions or stability, e.g. by coating or irradiation of surface, by reduction of non-specific binding, by promotion of specific binding} - G01N 33/56938: {Staphylococcus} - G01N 33/6854: {Immunoglobulins} - C07K 2319/00: Fusion polypeptide - C07K 2319/20: containing a tag with affinity for a non-protein ligand - G01N 2333/31: from Staphylococcus (G) - G01N 2333/315: from Streptococcus (G), e.g. Enterococci - C07K: PEPTIDES (peptides in foodstuffs A23; obtaining protein compositions for foodstuffs, working-up proteins for foodstuffs A23J; preparations for medicinal purposes A61K; peptides containing beta-lactam rings C07D; cyclic dipeptides not having in their molecule any other peptide link than those which form their ring, e.g. piperazine-2,5-diones, C07D; ergot alkaloids of the cyclic peptide type C07D519/02; macromolecular compounds having statistically distributed amino acid units in their molecules, i.e. when the preparation does not provide for a specific; but for a random sequence of the amino acid units, homopolyamides and block copolyamides derived from amino acids C08G69/00; macromolecular products derived from proteins C08H1/00; preparation of glue or gelatine C09H; single cell proteins, enzymes C12N; genetic engineering processes for obtaining peptides C12N15/00; compositions for measuring or testing processes involving enzymes C12Q; investigation or analysis of biological material G01N33/00) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract The present invention relates to an N-terminal cysteine-tagged Streptococcal protein G variant. Since the variant binds in a directional manner to a surface of a biochip or a biosensor, the variant provides a biochip and a biosensor having an improved antibody-immobilizing capability, compared with an untagged protein G variant. ## Claims ### Claim 1 An N-terminal cysteine-tagged Streptococcal protein G variant, represented by the following formula: Metx-(Cys)n-Ly-protein G-Qz wherein Met is methionine; L is a linker; protein G comprises two antibody-binding domains B1 and B2 of protein G obtained from Streptococcus; Q is a tag for protein purification; x, y and z are each 0 or 1; and n is a number from 1 to 10, wherein the antibody-binding domain B1 is represented by SEQ ID NO: 1, and the antibody-binding domain B2 is represented by SEQ ID NO: 2, and wherein the antibody-binding domain B1 has a deletion of 10 amino acid residues at its N-terminus. ### Claim 2 (depends on 1) The N-terminal cysteine-tagged Streptococcal protein G variant according to claim 1, wherein the cysteine tag consists of 1 to 5 cysteine residues. ### Claim 3 (depends on 1) The N-terminal cysteine-tagged Streptococcal protein G variant according to claim 1, wherein the cysteine tag consists of three cysteine residues. ### Claim 4 (depends on 1) The N-terminal cysteine-tagged Streptococcal protein G variant according to claim 1, wherein the linker consists of four asparagine residues and one lysine residue. ### Claim 5 (depends on 1) A nucleic acid sequence encoding the N-terminal cysteine-tagged Streptococcal protein G variant according to claim 1. ### Claim 6 (depends on 5) An expression vector comprising the nucleic acid sequence according to claim 5. ### Claim 7 (depends on 6) A host cell selected from the group consisting of KCTC 10948BP, KCTC 10949BP, KCTC 10950BP, KCTC 10951BP and KCTC 10952BP, wherein the host cell comprises the expression vector according to claim 6. ### Claim 8 (depends on 7) A method for producing a protein G variant, the method comprising culturing the host cell according to claim 7, and separating the protein G variant therefrom. ### Claim 9 (depends on 1) A biochip or biosensor comprising the N-terminal cysteine-tagged Streptococcal protein G variant according to claim 1, wherein the protein G variant is immobilized on a surface of a solid support. ### Claim 10 (depends on 9) The biochip or biosensor according to claim 9, wherein the solid support is selected from ceramics, glass, polymer, silicone and metal. ### Claim 11 (depends on 10) The biochip or biosensor according to claim 10, wherein the metal is gold. ### Claim 12 (depends on 9) The biochip or biosensor according to claim 9, further comprising an antibody which binds to the cysteine-tagged Streptococcal protein G variant immobilized on the surface of a solid support. ### Claim 13 (depends on 9) The biochip or biosensor according to claim 9, wherein the surface of the solid support is modified with any one group selected from a maleimide group, an epoxy group, a nitrophenol proline group and a methyl iodide group. ### Claim 14 (depends on 13) The biochip or biosensor according to claim 13, wherein the cysteine-tagged Streptococcal protein G variant is covalently bonded through a thiol group to any one of a maleimide group, an epoxy group, a nitrophenol proline group and a methyl iodide group on the surface of the solid support. ### Claim 15 (depends on 12) A method of analyzing an antigen using the biochip or biosensor according to claim 12.