Immunoglobulin-binding protein and affinity support using same

An affinity support, comprising:

• a solid-phase support, and
• an immunoglobulin-binding protein immobilized onto the solid-phase support,
• the immunoglobulin-binding protein comprising a mutant immunoglobulin-binding domain, and
• the mutant immunoglobulin-binding domain consisting of an amino acid sequence having at least 85% identity with an amino acid sequence of any of SEQ ID NOs:
• 1 to 12,
• wherein the amino acid sequence of the mutant immunoglobulin-binding domain has at least one mutation selected from the group consisting of the following mutations (a) to (d):
• (a) a substitution of Lys with another amino acid residue, a deletion of Lys, or an insertion of another amino acid residue at a position before or after Lys at a position corresponding to position 58 of the amino acid sequence of SEQ ID NO:
• 3;
• (b) a substitution of Lys with another amino acid residue, a deletion of Lys, or an insertion of another amino acid residue at a position before or after Lys at a position corresponding to position 50 of the amino acid sequence of SEQ ID NO:
• 3;
• (c) a substitution of Lys with another amino acid residue, a deletion of Lys, or an insertion of another amino acid residue at a position before or after Lys at a position corresponding to position 49 of the amino acid sequence of SEQ ID NO:
• 3;
• and
• (d) a substitution of Lys with another amino acid residue, a deletion of Lys, or an insertion of another amino acid residue at a position before or after Lys at a position corresponding to position 42 of the amino acid sequence of SEQ ID NO:
• 3, and
• the amino acid sequence of the mutant immunoglobulin-binding domain has Lys at at least one position selected from the group consisting of positions corresponding to positions 4, 7, and 35 in the amino acid sequence of SEQ ID NO:
• 3,
• wherein the solid-phase support and the immunoglobulin-binding protein are immobilized via a linker,
• the linker comprises a polyethylene glycol chain and an epoxy group, a carboxy group, a (meth)acrylic group, an aldehyde group, or a succinimidyl group,
• the linker has a length is from 40 to 300, wherein the linker length is the total of a chain length of the polyethylene glycol chain and the number of carbon atoms derived from the epoxy group, carboxy group, a (meth)acrylic group, an aldehyde group, or a succinimidyl group.