Analysis of Heterogeneity of IgG-Binding Proteins Expressed by Group A Streptococci

Methods for analyzing the functional heterogeneity of type II IgG-binding proteins expressed by group A streptococci are described. Evidence for two major antigenic classes of type II IgG-binding proteins is presented. Heterogeneity in functional binding profiles was found to be associated with proteins belonging to either antigenic class. The antigenic class of IgG-binding protein was found to correlate with the antigenic class of M protein expressed by the same group A isolate. For certain group A isolates, the IgG-binding protein and M protein were shown to be a single molecule.