A Novel MHC-I Surface Targeted for Binding by the MCMV m06 Immunoevasin Revealed by Solution NMR.
 

A Novel MHC-I Surface Targeted for Binding by the MCMV m06 Immunoevasin Revealed by Solution NMR.

Related Articles A Novel MHC-I Surface Targeted for Binding by the MCMV m06 Immunoevasin Revealed by Solution NMR.

J Biol Chem. 2015 Oct 13;

Authors: Sgourakis NG, May NA, Boyd LF, Ying J, Bax A, Margulies DH

Abstract
As part of its strategy to evade detection by the host immune system, murine cytomegalovirus (MCMV) encodes three proteins that modulate cell surface expression of major histocompatibility complex class I (MHC-I) molecules: the MHC-I homolog m152/gp40, as well as the m02-m16 family members m04/gp34 and m06/gp48. Previous studies of the m04 protein revealed a divergent immunoglobulin (Ig)-like fold that is unique to immunoevasins of the m02-m16 family. Here, we engineer and characterize recombinant m06 and investigate its interactions with full length and truncated forms of the MHC-I molecule H2-L(d) by several techniques. Furthermore, we employ solution NMR to map the interaction footprint of the m06 protein on MHC-I, taking advantage of a truncated H2-L(d), "mini-H2-L(d)", consisting of only the ?1?2 platform domain. Mini-H2-L(d), refolded in vitro with a high-affinity peptide yields a molecule that shows outstanding NMR spectral features, permitting complete backbone assignments. These NMR-based studies reveal that m06 binds tightly to a discrete site located under the peptide-binding platform that partially overlaps with the ?2-microglobulin (?2m) interface on the MHC-I heavy chain, consistent with in vitro binding experiments showing significantly reduced complex formation between m06 and ?2m-associated MHC-I. Moreover, we carry out NMR relaxation experiments to characterize the ps-ns dynamics of the free mini-H2-L(d) MHC-I molecule, revealing that the site of interaction is highly ordered. This study provides insight into the mechanism of the interaction of m06 with MHC-I, suggesting a structural manipulation of the target MHC-I molecule at an early stage of the peptide-loading pathway.


PMID: 26463211 [PubMed - as supplied by publisher]



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