Patent ID: 8541005

Claim:
An N-terminal cysteine-tagged Streptococcal protein G variant, represented by the following formula: Met x -(Cys)n-L y -protein G-Q z 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.