Novel modified proteins of the cell membrane extracellular domain of Protein g

PROBLEM TO BE SOLVED: To provide a novel protein, etc. with decreased binding property to the Fc region of immunoglobulin and/or the Fab region thereof in a weakly acidic region and an elution pH shifted to a weakly acidic side.SOLUTION: The present invention provides a protein having binding activity to Fc region of immunoglobulin (IgG). Compared with a protein consisting of G and B domains of a wild-type protein, the binding activity of the protein in a weakly acidic region to the Fc region of IgG is decreased by substituting a positively charged residue of protein G for a residue in the vicinity of the positively charged residue of protein G. The present invention also provides an agent for capturing a protein having IgG or the Fc region or Fab region of IgG, the protein being immobilized on a water-insoluble solid support. The present invention further provides affinity chromatography for purification of the protein having IgG or the Fc region or Fab region of IgG, including such a capture agent and purifying method of the protein having the IgG or the Fc region or Fab region of IgG using the chromatography.SELECTED DRAWING: Figure 6