Crystal structure of the HLA-DM-HLA-DR1 complex defines mechanisms for rapid peptide selection

Cell. 2012 Dec 21;151(7):1557-68. doi: 10.1016/j.cell.2012.11.025.

Abstract

HLA-DR molecules bind microbial peptides in an endosomal compartment and present them on the cell surface for CD4 T cell surveillance. HLA-DM plays a critical role in the endosomal peptide selection process. The structure of the HLA-DM-HLA-DR complex shows major rearrangements of the HLA-DR peptide-binding groove. Flipping of a tryptophan away from the HLA-DR1 P1 pocket enables major conformational changes that position hydrophobic HLA-DR residues into the P1 pocket. These conformational changes accelerate peptide dissociation and stabilize the empty HLA-DR peptide-binding groove. Initially, incoming peptides have access to only part of the HLA-DR groove and need to compete with HLA-DR residues for access to the P2 site and the hydrophobic P1 pocket. This energetic barrier creates a rapid and stringent selection process for the highest-affinity binders. Insertion of peptide residues into the P2 and P1 sites reverses the conformational changes, terminating selection through DM dissociation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Crystallography, X-Ray
  • HLA-D Antigens / chemistry*
  • HLA-D Antigens / metabolism*
  • HLA-DR1 Antigen / chemistry*
  • HLA-DR1 Antigen / metabolism*
  • Humans
  • Hydrophobic and Hydrophilic Interactions
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Conformation
  • Protein Interaction Domains and Motifs
  • Sequence Alignment

Substances

  • HLA-D Antigens
  • HLA-DM antigens
  • HLA-DR1 Antigen

Associated data

  • PDB/4GBX
  • PDB/4HPQ