Substitution of asparagine³²⁴ with aspartic acid in the fc portion of mouse antibodies reduces their capacity for clq binding

The sequence of the heavy chain C region of mouse mutant IgG_2a antibodies with reduced capacity for Clq binding but with retained ability for Fc receptor‐mediated functions was determined by cDNA cloning and by mRNA sequencing. The specific mutation was found to be the substitution of asparagine³²⁴ with aspartic acid. Asparagine³²⁴ represents a new residue relating to the Clq‐binding sites previously described.