2f74
From Proteopedia
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Murine MHC class I H-2Db in complex with human b2-microglobulin and LCMV-derived immunodminant peptide gp33
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Overview
beta(2)-Microglobulin (beta(2)m) is non-covalently linked to the major, histocompatibility complex (MHC) class I heavy chain and interacts with, CD8 and Ly49 receptors. Murine MHC class I heavy chains can bind human, beta(2)m (hbeta(2)m) and peptide, and such hybrid molecules are often used, in structural and functional studies. The replacement of mouse beta(2)m, (mbeta(2)m) with hbeta(2)m has several functional consequences for MHC, class I complex stability and specificity, but the structural basis for, this is presently unknown. To investigate the impact of species-specific, beta(2)m subunits on MHC class I conformation, we provide a, crystallographic comparison of H-2D(b) in complex with LCMV-derived gp33, peptide and either hbeta(2)m or mbeta(2)m. The conformation of the gp33, peptide is not affected by the beta(2)m species. Comparison of the, interface between beta(2)m and the alpha(1)alpha(2) domains of the heavy, chain in these two crystal structures reveals a marked increase in both, polarity and number of hydrogen bonds between hbeta(2)m and the, alpha(1)alpha(2) domains of H-2D(b). We propose that the positioning of, two hydrogen bond rich regions at the hbeta(2)m/alpha(1)alpha(2) interface, plays a central role in the increased overall stability and peptide, exchange capacity in the H-2D(b)/hbeta(2)m complex. These two regions act, as bridges, holding and stabilizing the underside of the alpha(1) and, alpha(2) helices, enabling a prolonged peptide-receptive conformation of, the peptide binding cleft. Furthermore, analysis of H-2D(b) in complex, with either mbeta(2)m or hbeta(2)m provides a structural explanation for, the differential binding of H-2D(b)/hbeta(2)m to both Ly49A and Ly49C. Our, comparative structural study emphasizes the importance of beta(2)m, residues at positions 3, 6 and 29 for binding to Ly49A and suggests that, sterical hindrance by residue K6 on hbeta(2)m impairs the recognition of, Ly49C by H-2D(b)/gp33/hbeta(2)m. Finally, comparison of the two H-2D(b), crystal structures implies that the beta(2)m species may affect the, strength of TCR recognition by affecting CD8 binding.
Disease
Known disease associated with this structure: Hypoproteinemia, hypercatabolic OMIM:[109700]
About this Structure
2F74 is a Protein complex structure of sequences from Homo sapiens and Mus musculus. Full crystallographic information is available from OCA.
Reference
Structural basis of the differential stability and receptor specificity of H-2Db in complex with murine versus human beta2-microglobulin., Achour A, Michaelsson J, Harris RA, Ljunggren HG, Karre K, Schneider G, Sandalova T, J Mol Biol. 2006 Feb 17;356(2):382-96. Epub 2005 Dec 7. PMID:16375919
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