Qa-2 molecules are peptide receptors of higher stringency than ordinary class I molecules.
Class I molecules of the major histocompatibility complex (MHC) transport peptides to the cell surface for surveillance by T cells. Ligand specificity is stringent and differs from allele to allele. Here we report analysis of natural ligands of 'unconventional' glycophosphatidyl-anchored mouse class I molecules, Qa-2. The function of these molecules is unclear; they can serve as recognition structures for 'unrestricted' cytotoxic T cells but have not been found to present peptides to T cells, although the DNA sequence suggests a similar peptide binding groove to that of 'conventional' class I molecules, and other unconventional class I molecules can present antigens in a few cases. Pool sequencing of natural Qa-2 ligands shows that Qa-2 molecules are indeed peptide receptors, having ligand specificity similar to that of conventional class I molecules, that is, a predominant length of nine amino acids, anchor positions, and hydrophobic termination of peptides. But ligand specificity is much more stringent than with other class I molecules: of the nine positions, two are anchors and four have rather limited occupancy.
Rötzschke
O
O
Max-Planck-Institut für Biologie, Abteilung Immungenetik, Tübingen, Germany.
Falk
K
K
Stevanović
S
S
Grahovac
B
B
Soloski
M J
MJ
Jung
G
G
Rammensee
H G
HG
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000378:metabolism
D015395:Histocompatibility Antigens Class I; D010455:Peptides; C032907:Q surface antigens