IDENTIFICATION OF AN AMINO-ACID SIGNATURE SEQUENCE PREDICTIVE OF PROTEIN G-INHIBITABLE IGG(3)-BINDING ACTIVITY IN GROUP-A STREPTOCOCCAL IGG-BINDING PROTEINS

Sequence comparison of six known group-A streptococcal IgG-binding pro teins, sharing the common property of protein G-inhibitable IgG(3)-bin ding-activity, identified a highly conserved 35-amino-acid (aa) sequen ce (74-100% similarity) within an EQ-rich central conserved core regio n of each protein. A search of aa sequence databases identified four a dditional proteins with > 50% similarity to this consensus sequence. A ll of these proteins demonstrated protein G-inhibitable IgG(3)-binding activity. Taken together, these results identify a signature sequence that predicts the presence of a protein G-inhibitable IgG(3)-binding domain(s) in group-A streptococcal IgG-binding proteins.