1pyw

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Revision as of 16:42, 12 November 2007

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spinqualitylabelsall models 1pyw, resolution 2.1Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Human class II MHC protein HLA-DR1 bound to a designed peptide related to influenza virus hemagglutinin, FVKQNA(MAA)AL, in complex with staphylococcal enterotoxin C3 variant 3B2 (SEC3-3B2)

Overview

Crystal structures of the class II major histocompatibilty complex (MHC), protein, HLA-DR1, generally show a tight fit between MHC and bound peptide, except in the P6/P7 region of the peptide-binding site. In this region, there is a shallow water-filled pocket underneath the peptide and between, the pockets that accommodate the P6 and P7 side chains. We investigated, the properties of this pocket with the idea of engineering substitutions, into the corresponding region of peptide antigens to increase their, binding affinity for HLA-DR1. We investigated d-amino acids and N-alkyl, modifications at both the P6 and P7 positions of the peptide and found, that binding of peptides to HLA-DR1 could be increased by incorporating an, N-methyl substitution at position 7 of the peptide. The crystal structure, of HLA-DR1 bound to a peptide containing a P7 N-methyl alanine was, determined. The N-methyl group orients in the P6/P7 pocket, displacing one, of the waters usually bound in this pocket. The structure shows that the, substitution does not alter the conformation of the bound peptide, which, adopts the usual polyproline type II helix. An antigenic peptide carrying, the N-methyl modification is taken up by antigen-presenting cells and, loaded onto endogenous class II MHC molecules for presentation, and the, resultant MHC-peptide complexes activate antigen-specific T-cells. These, results suggest a possible strategy for increasing the affinity of weakly, immunogenic peptides that might be applicable to the development of, vaccines and diagnostic reagents.

About this Structure

1PYW is a Protein complex structure of sequences from Homo sapiens and Staphylococcus aureus with ACE as ligand. Full crystallographic information is available from OCA.

Reference

Exploration of the P6/P7 region of the peptide-binding site of the human class II major histocompatability complex protein HLA-DR1., Zavala-Ruiz Z, Sundberg EJ, Stone JD, DeOliveira DB, Chan IC, Svendsen J, Mariuzza RA, Stern LJ, J Biol Chem. 2003 Nov 7;278(45):44904-12. Epub 2003 Sep 1. PMID:12952957

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