1SXT

STAPHYLOCOCCAL ENTEROTOXIN TYPE A (SEA) CO-CRYSTALLISED WITH ZINC

Summary for 1SXT

• Entry DOI: 10.2210/pdb1sxt/pdb
• Descriptor: STAPHYLOCOCCAL ENTEROTOXIN TYPE A, ZINC ION (2 entities in total)
• Functional Keywords: superantigen, staphylococcus, enterotoxin, toxin
• Biological source: Staphylococcus aureus
• Cellular location: Secreted: P0A0L2
• Total number of polymer chains: 2
• Total formula weight: 54391.43

Authors

Sundstrom, S.M. (deposition date: 1996-11-14, release date: 1997-11-19, Last modification date: 2024-10-30)

Primary citation

Sundstrom, M.,Hallen, D.,Svensson, A.,Schad, E.,Dohlsten, M.,Abrahmsen, L.
The Co-crystal structure of staphylococcal enterotoxin type A with Zn2+ at 2.7 A resolution. Implications for major histocompatibility complex class II binding.
J.Biol.Chem., 271:32212-32216, 1996

PubMed Abstract: 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.

PubMed: 8943278
DOI: 10.1074/jbc.271.50.32212

Experimental method

X-RAY DIFFRACTION (2.7 Å)