Protein ligand for affinity isolation matrix

A protein, comprising three or more amino acid sequences derived from any domain selected from E, D, A, B, and C domains of Protein A, the amino acid sequences comprising amino acid substitutions for all lysine residues (Lys) in the domains,

• wherein the amino acid sequences are connected to one another through one or more linkers,
• wherein (i) at least two of the linkers contain a lysine residue (Lys) or a cysteine residue (Cys), or
• (ii) at least one of the linkers contains a lysine residue or a cysteine residue, and a region within 4 or less residues from N- or C-terminus of the protein comprises a lysine residue or a cysteine residue,
• at least 90% of the following amino acid residues:
• Gln-9, Gln-10, Phe-13, Tyr-14, Leu-17, Pro-20, Asn-21, Leu-22, Gln-26, Arg-27, Phe-30, Ile-31, Leu-34, Pro-38, Ser-39, Leu-45, Leu-51, Asn-52, Gln-55, and Pro-57 (the residue numbers indicated are corresponding residue numbers of the C domain and the positions of the conserved amino acids for any domain selected from E, D, A and B domains are respectively compared to the C domain positions upon alignment with the C domain of any domain selected from E, D, A and B domains) are conserved in any domain selected from E, D, A, B, and C domains in the protein, and
• the amino acid sequences having at least 80% sequence identity to the amino acid sequences of the E, D, A, B, or C domains before the lysine substitutions.