Localization of Binding Sites of Staphylococcal Enterotoxin B (SEB), aSuperantigen, for HLA-DR by Inhibition with Synthetic Peptides of SEB

摘要

Staphylococcal enterotoxins are major causes of food poisoning and toxic shocksyndrome. Their ability to bind to major histocompatibility complex (MHC) class II molecules has been suggested to be the first step in the mechanism by which they cause illness. By flow cytometric analysis, the sites of interaction of staphylococcal enterotoxin B (SEB) with HLA-DR molecules were probed in the present study by inhibiting the binding of biotinylated SEB with synthetic peptides of SEB. Five peptides of SEB gave significant inhibition of binding: a peptide containing amino acids 9 to 20 SEB(9-20), SEB(30-3a), SEB(61-70), SEB(90-114), and SEB(169-181).One peptide, SEB(39-51), enhanced binding. Among the inhibitory peptides, SEB(90-114), a peptide spanning the entire disulfide loop, showed the most efficient inhibition of binding. Peptides SEB(9-20) and SEB(39-51) include amino acid residues that have been identified by point mutation studies (J.W. Kappler, A. Herman, J. Clements, and P. Marrack, J. Exp. Med. 175:387-389, 1992) as being important in binding to MHC class II. only two of the residues that line the a5 groove, His-12 and Tyr-17, are on a peptide that inhibits binding.