Identification of HLA-DRα chain residues critical for binding of the toxic shock syndrome toxin superantigen

Staphylococcal toxic shock syndrome toxin 1 (TSST-1) binds to major histocompatibility complex class II molecules, and the toxin-class II complexes induce proliferation of T ceils expressing Vβ2 sequences. To define the residues involved in TSST-1 binding, a set of transfectants expressing 21 HLA-DRα chain mutants were analyzed for their abilities to bind and present TSST-1 and to present an antigenic peptide. Mutations at DRα positions 36 and 39 markedly decreased the ability of the DR7 molecule to bind and present TSST-1 but did not affect the ability to present an antigenic peptide. These data indicate that DRα residues 36 and 39, predicted to be located on an outer loop, are important in the formation of the TSST-1 binding site on DR molecules. © 1992, Rockefeller University Press., All rights reserved.