2g9h

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spinqualitylabelsall models 2g9h, resolution 2.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal Structure of Staphylococcal Enterotoxin I (SEI) in Complex with a Human MHC class II Molecule

Overview

Superantigens are bacterial or viral proteins that elicit massive T cell, activation through simultaneous binding to major histocompatibility, complex (MHC) class II and T cell receptors. This activation results in, uncontrolled release of inflammatory cytokines, causing toxic shock. A, remarkable property of superantigens, which distinguishes them from T cell, receptors, is their ability to interact with multiple MHC class II alleles, independently of MHC-bound peptide. Previous crystallographic studies have, shown that staphylococcal and streptococcal superantigens belonging to the, zinc family bind to a high affinity site on the class II beta-chain., However, the basis for promiscuous MHC recognition by zinc-dependent, superantigens is not obvious, because the beta-chain is polymorphic and, the MHC-bound peptide forms part of the binding interface. To understand, how zinc-dependent superantigens recognize MHC, we determined the crystal, structure, at 2.0 A resolution, of staphylococcal enterotoxin I bound to, the human class II molecule HLA-DR1 bearing a peptide from influenza, hemagglutinin. Interactions between the superantigen and DR1 beta-chain, are mediated by a zinc ion, and 22% of the buried surface of peptide.MHC, is contributed by the peptide. Comparison of the staphylococcal, enterotoxin I.peptide.DR1 structure with ones determined previously, revealed that zinc-dependent superantigens achieve promiscuous binding to, MHC by targeting conservatively substituted residues of the polymorphic, beta-chain. Additionally, these superantigens circumvent peptide, specificity by engaging MHC-bound peptides at their conformationally, conserved N-terminal regions while minimizing sequence-specific, interactions with peptide residues to enhance cross-reactivity.

About this Structure

2G9H is a Protein complex structure of sequences from Homo sapiens and Staphylococcus aureus with ZN, SO4, EPE and DIO as ligands. Full crystallographic information is available from OCA.

Reference

Crystal structure of staphylococcal enterotoxin I (SEI) in complex with a human major histocompatibility complex class II molecule., Fernandez MM, Guan R, Swaminathan CP, Malchiodi EL, Mariuzza RA, J Biol Chem. 2006 Sep 1;281(35):25356-64. Epub 2006 Jul 6. PMID:16829512

Page seeded by OCA on Mon Nov 12 22:16:24 2007