1sxt
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STAPHYLOCOCCAL ENTEROTOXIN TYPE A (SEA) CO-CRYSTALLISED WITH ZINC
OverviewOverview
Superantigens form complexes with major histocompatibility complex (MHC), class II molecules and T-cell receptors resulting in extremely strong, immunostimulatory properties. Staphylococcus aureus enterotoxin A (SEA), belongs to a subgroup of the staphylococcal superantigens that utilizes, Zn2+ in the high affinity interaction with MHC class II molecules. A high, affinity metal binding site was described previously in SEA, co-crystallized with Cd2+ in which the metal ion was octahedrally, co-ordinated, involving the N-terminal serine. We have now co-crystallized, SEA with its native co-factor Zn2+ and determined its crystal structure at, 2.7 A resolution. As expected for a Zn2+ ion, the co-ordination was found, to be tetrahedral. Three of the ligands are located on the SEA surface on, a C-terminal domain beta-sheet, while the fourth varies with the, conditions. Further analysis of the zinc binding event was performed using, titration microcalorimetry, which showed that SEA binds Zn2+ with an, affinity of KD = 0.3 microM in an entropy driven process. The differential, Zn2+ co-ordination observed here has implications for the mechanism of the, SEA-MHC class II interaction.
About this StructureAbout this Structure
1SXT is a Single protein structure of sequence from Staphylococcus aureus with ZN as ligand. Full crystallographic information is available from OCA.
ReferenceReference
The Co-crystal structure of staphylococcal enterotoxin type A with Zn2+ at 2.7 A resolution. Implications for major histocompatibility complex class II binding., Sundstrom M, Hallen D, Svensson A, Schad E, Dohlsten M, Abrahmsen L, J Biol Chem. 1996 Dec 13;271(50):32212-6. PMID:8943278
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