Multimeric immunoglobulin-binding domain

An immunoglobulin-binding protein as a multimer of immunoglobulin binding domains represented by the following general formula:

• (R1)n-(R2)m, or (R2)m-(R1)n,
• wherein R2 is an immunoglobulin-binding domain occurring at the N-terminus or the C-terminus of the protein, and that includes an amino acid residue that covalently bonds to an insoluble support upon immobilization reaction with the insoluble support, and R1 is an immunoglobulin-binding domain that does not contain an amino acid residue the presence of which in the sequence compared to when it is absent in the sequence reduces the immunoglobulin-binding activity of the support yielded by the immobilization reaction,
• the immunoglobulin-binding domains comprising an amino acid sequence with the left end representing the N-terminus and the right end representing the C-terminus,
• the immunoglobulin-binding protein having properties that satisfy the following conditions, and that allow the immunoglobulin-binding protein to be immobilized on the insoluble support via the amino acid residue of the (R2) domain:
• (1) n is an integer of 5 to 9;
• (2) m is an integer of 1 or 2;
• (3) the n (R1) domains may or may not have the same sequence;
• and
• (4) the total number of domains (n+m) is 6 to 10,
• wherein the immunoglobulin-binding domains (R1) and (R2) each comprise a domain modified from the amino acid sequence of an immunoglobulin-binding domain of Staphylococcus protein A,
• wherein the (R1) domain of the general formula comprises an amino acid sequence of the immunoglobulin-binding domain of Staphylococcus protein A in which the lysine residues originally present in the sequence are substituted with a non-lysine amino acid at 1 to 3 of positions 4, 7, and 35, and without any amino acid substitution with a lysine residue, and
• wherein the (R2) domain of the general formula comprises an amino acid sequence of the immunoglobulin-binding domain of Staphylococcus protein A which includes substitution of 1 to 6 amino acid residues with lysine at positions 40, 43, 46, 53, 54, and 56.