4PG9: MHC Class I in complex with Sendai virus nucleoprotein peptide FAPGNYPAL

MHC class I molecules present a variable but limited repertoire of antigenic peptides for T-cell recognition. Understanding how peptide selection is achieved requires mechanistic insights into the interactions between the MHC I and candidate peptides. We find that, at first encounter, MHC I H-2K(b) considers a wide range of peptides, including those with expanded N termini and unfitting anchor residues. Discrimination occurs in the second step, when noncanonical peptides dissociate with faster exchange rates. This second step exhibits remarkable temperature sensitivity, as illustrated by numerous noncanonical peptides presented by H-2K(b) in cells cultured at 26 degrees C relative to 37 degrees C. Crystallographic analyses of H-2K(b)-peptide complexes suggest that a conformational adaptation of H-2K(b) drives the decisive step in peptide selection. We propose that MHC class I molecules consider initially a large peptide pool, subsequently refined by a temperature-sensitive induced-fit mechanism to retain the canonical peptide repertoire.
PDB ID: 4PG9Download
MMDB ID: 125905
PDB Deposition Date: 2014/5/1
Updated in MMDB: 2017/12
Experimental Method:
x-ray diffraction
Resolution: 2.4  Å
Source Organism:
Mus musculus
Similar Structures:
Biological Unit for 4PG9: trimeric; determined by author and by software (PISA)
Molecular Components in 4PG9
Label Count Molecule
Proteins (3 molecules)
H-2 Class I Histocompatibility Antigen, K-B Alpha Chain(Gene symbol: H2-K1)
Molecule annotation
Beta-2-microglobulin(Gene symbol: B2m)
Molecule annotation
Sendai Virus Nucleoprotein
Molecule annotation
Chemicals (10 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB