Conformational lability in the class II MHC 310 helix and adjacent extended strand dictate HLA-DM susceptibility and peptide exchange.Painter, C.A., Negroni, M.P., Kellersberger, K.A., Zavala-Ruiz, Z., Evans, J.E., Stern, L.J.
(2011) Proc Natl Acad Sci U S A 108: 19329-19334
- PubMed: 22084083
- DOI: https://doi.org/10.1073/pnas.1108074108
- Primary Citation of Related Structures:
- PubMed Abstract:
HLA-DM is required for efficient peptide exchange on class II MHC molecules, but its mechanism of action is controversial. We trapped an intermediate state of class II MHC HLA-DR1 by substitution of αF54, resulting in a protein with increased HLA-DM binding affinity, weakened MHC-peptide hydrogen bonding as measured by hydrogen-deuterium exchange mass spectrometry, and increased susceptibility to DM-mediated peptide exchange. Structural analysis revealed a set of concerted conformational alterations at the N-terminal end of the peptide-binding site. These results suggest that interaction with HLA-DM is driven by a conformational change of the MHC II protein in the region of the α-subunit 3(10) helix and adjacent extended strand region, and provide a model for the mechanism of DM-mediated peptide exchange.
Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 10655, USA.