THE MOLECULAR ARCHITECTURE OF TWO MICROBIAL SUPERANTIGENS A.C. Papageorgiou¹, H.S. Tranter², R.D. Brehm² & K.R. Acharya¹. ¹School of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK. ²Developmental Production Department, Production Division, Centre for Applied Microbiology and Research, Porton Down, Salisbury SP4 OJG, UK.

Staphylococcal enterotoxins (SEs) and toxic shock syndrome toxin-1 (TSST-1) are a family of structurally related proteins that are produced by Staphylococcus aureus and have dramatic effects on the immune system. Studies with SEs and TSST-1 have revealed these to be highly polyclonal activators of T-cells in the presence of cells having class II antigens of the major histocompatibility complex (MHC class II). These toxins act at nanomolar concentrations and are not processed internally like with normal antigens. Each toxin type is capable of stimulating subpopulations of peripheral T lymplocytes possessing a specific variable [[beta]] (V[[beta]] segment of the T-cell receptor (TcR) and have been classified as superantigens. We have determined the 3D crystal structure of TSST-1 and SEC2 at 2.5Å and 2.0Å resolution, respectively (Acharya et al., 1994; Papageorgiou et al., 1995). The overall architecture of these molecules is similar to other known superantigen structures, namely SEB (Swaminathan et al., 1992) and SEA (Schad et al., 1995). A detailed comparison of the different modes of MHC class II and TcR binding adapted by this family of molecules will be presented.

Acharya, K.R. et al. (1994) Nature 367, 94-97.

Papageorgiou, A.C. et al. (1995) Structure 3, 769-779.

Schad, E. et al. (1995) EMBO J. 14, 3292-3301.

Swaminathan, S. et al. (1992) Nature 359, 801-806.