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Superantigens stimulate T cells bearing particular T-cell receptor V beta sequences, so they are extremely potent polyclonal T-cell mitogens. T-cell activation is preceded by binding of superantigens to class II major histocompatibility complex (MHC) molecules. To further the structural characterization of these interactions, the crystal structure of a toxin associated with toxic-shock syndrome, TSST-1, which is a microbial superantigen, has been determined at 2.5 A resolution. The N- and C-terminal domains of the structure both contain regions involved in MHC class II association; the C-terminal domain is also implicated in binding the T-cell receptor. Despite low sequence conservation, the TSST-1 topology is similar to the structure reported for the superantigen staphylococcal enterotoxin B4. But TSST-1 lacks several of the structural features highlighted as central to superantigen activity in the staphylococcal enterotoxin B and we therefore reappraise the structural basis of superantigen action.

Original publication




Journal article



Publication Date





94 - 97


Amino Acid Sequence, Bacterial Toxins, Computer Graphics, Crystallography, X-Ray, Enterotoxins, Histocompatibility Antigens Class II, Molecular Sequence Data, Protein Conformation, Protein Structure, Secondary, Receptors, Antigen, T-Cell, alpha-beta, Staphylococcus aureus, Structure-Activity Relationship, Superantigens