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Nat Struct Biol. 1997 Aug;4(8):635-43.

Crystal structure of the streptococcal superantigen SPE-C: dimerization and zinc binding suggest a novel mode of interaction with MHC class II molecules.

Author information

  • 1Department of Biochemistry, Massey University, Palmerston North, New Zealand.

Abstract

Bacterial superantigens are small proteins that have a very potent stimulatory effect on T lymphocytes through their ability to bind to both MHC class II molecules and T-cell receptors. We have determined the three-dimensional structure of a Streptococcal superantigen, SPE-C, at 2.4 A resolution. The structure shows that SPE-C has the usual superantigen fold, but that the surface that forms a generic, low-affinity MHC-binding site in other superantigens is here used to create a SPE-C dimer. Instead, MHC class II binding occurs through a zinc binding site that is analogous to a similar site in staphylococcal enterotoxin A. Consideration of the SPE-C dimer suggests a novel mechanism for promotion of MHC aggregation and T-cell activation.

PMID:
9253413
[PubMed - indexed for MEDLINE]
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