IgA-SPECIFIC PROTEINS OF PATHOGENIC BACTERIA
In the present review, data about structure and specificity of bacterial IgA-receptors (IgA-binding M-like proteins Arp4 and Sir22 from serogroup A hemolytic streptococci, P-antigen from serogroup В hemolytic streptococci, and SSL family proteins from Staphylococcus aureus) are surveyed. The principal conclusion derived from the comparison is the fact that all bacterial receptors bind the same site in the IgA molecule overlapped with the binding site of the endogenous human IgA receptor CD89. We speculate that this site composed with spatially close amino acid strands Leu257-Gly259 in domain Ca2 and Pro440-Phe443 in domain Ca3 is subjected to a conformational rearrangement induced with binding of the antigen in the IgA active center.