Single amino acid substitution in the mouse IgG1 Fc region induces drastic enhancement of the affinity to protein A.

The purification of monoclonal antibody sometimes requires a lot of time and involves complicated steps because of the poorer ability of mouse IgG to interact with protein A, or also with protein G, than IgGs from other species such as those of human and rabbit. To resolve this problem, we exchanged one or two amino acid residues of mouse IgG Fc region with that of human IgG. Three mutants (T252M, T254S and T252M-T254S) showed significant improvement in the affinity to protein A. The exchange of the threonine 252 residue to methionine (T252M) was most efficient. This result suggests that a direct and simple modification allows the efficient purification of monoclonal antibody and of fusion protein containing mouse IgG Fc region.