Crystal structures of two I-Ad-peptide complexes reveal that high affinity can be achieved without large anchor residues

Immunity. 1998 Mar;8(3):319-29. doi: 10.1016/s1074-7613(00)80537-3.


We have determined the structures of I-Ad covalently linked to an ovalbumin peptide (OVA323-339) and to an influenza virus hemagglutinin peptide (HA126-138). The floor of the peptide-binding groove contains an unusual beta bulge, not seen in I-E and DR structures, that affects numerous interactions between the alpha and beta chains and bound peptide. Unlike other MHC-peptide complexes, the peptides do not insert any large anchor residues into the binding pockets of the shallow I-Ad binding groove. The previously identified six-residue "core" binding motif of I-Ad occupies only the P4 to P9 pockets, implying that specificity of T cell receptor recognition of I-Ad-peptide complexes can be accomplished by peptides that only partially fill the MHC groove.

Publication types

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

MeSH terms

  • Animals
  • Binding Sites
  • Crystallography, X-Ray*
  • Dimerization
  • Hemagglutinin Glycoproteins, Influenza Virus / chemistry*
  • Histocompatibility Antigens Class II / chemistry*
  • Histocompatibility Antigens Class II / genetics
  • Mice
  • Models, Immunological
  • Models, Molecular
  • Molecular Sequence Data
  • Ovalbumin / chemistry*
  • Peptide Fragments / chemistry*
  • Recombinant Proteins / chemistry


  • HA 126-138
  • Hemagglutinin Glycoproteins, Influenza Virus
  • Histocompatibility Antigens Class II
  • I-Ad antigen
  • OVA 323-339
  • Peptide Fragments
  • Recombinant Proteins
  • Ovalbumin

Associated data

  • PDB/1IAO
  • PDB/2IAD