A natural mutation of the amino acid residue at position 60 destroys staphylococcal enterotoxin A murine T-cell mitogenicity.

摘要: A variety of techniques have been used to identify the amino acid residues bacterial superantigens involved in their interactions with major histocompatibility complex (MHC) class II and T-cell receptor (TCR). In this study, we isolated a naturally mutated staphylococcal enterotoxin (SEA) from three different Staphylococcus aureus strains, which at position 60 has changed aspartic (D) asparagine (N). We then studied influence change on immunological activities SEA. Our results demonstrated that mutation does not affect capacity SEA bind MHC molecules consequently activates human monocytes peripheral blood lymphocytes. contrast, failed stimulate proliferation murine splenic lymphocytes two when presented by molecules, it also activate cell line 3DT, expresses SEA-specific TCR V beta element (V 1). These indicate alters interaction between TCR. The reactivity patterns specific anti-SEA monoclonal antibodies suggested observed effect system might be due certain conformational changes molecule introduced upon changing D N. Site-directed mutagenesis N residue or glycine reconstituted ability effects natural cells highlight relevance affinity avidity SEA-TCR function species may reflect difference epitope specificity.