1i4g

Crystal structure of Staphylococcal enterotoxin A mutant H187A with reduced Zn2+ affinity

spinqualitylabelsall models 1i4g, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1i4g is a 2 chain structure with sequence from Staphylococcus aureus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.1Å Ligands: SO4, ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function ETXA_STAAU Staphylococcal enterotoxins cause the intoxication staphylococcal food poisoning syndrome. The illness is characterized by high fever, hypotension, diarrhea, shock, and in some cases death. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed The structure of a mutant form of staphylococcal enterotoxin A (SEA) has been determined to 2.1 A resolution. The studied SEA substitution H187-->A187 (SEAH187A) leads to an almost 10-fold reduction of the binding to major histocompatibility complex (MHC) class II. H187 is important for this interaction since it coordinates Zn2+. The zinc ion is thought to hold MHC class II and SEA together in a complex. Interestingly, only one of two molecules in the asymmetric unit binds Zn2+. H225, D227, a water molecule, and H44 from a symmetry-related molecule ligate Zn2+. The symmetry-related histidine is necessary for this substituted Zn2+ site to bind to Zn2+ at low zinc concentration (no Zn2+ added). Since a water molecule replaces the missing H187, H44 binds Zn2+ at the position where betaH81 from MHC class II probably will bind. Dynamic light scattering analysis reveals that in solution as well as in the crystal lattice the SEA(H187A) mutant forms aggregates. The substitution per se does not cause aggregation since wild-type SEA also forms aggregates. Addition of EDTA reduces the size of the aggregates, indicating a cross-linking function of Zn2+. In agreement with the biological function, the aggregation is weak (i.e. not revealed by gel filtration) and non-specific. Cooperative zinc binding in a staphylococcal enterotoxin A mutant mimics the SEA-MHC class II interaction.,Hakansson M, Antonsson P, Bjork P, Svensson LA J Biol Inorg Chem. 2001 Oct;6(8):757-62. PMID:11713682 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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