1kjm
TAP-A-associated rat MHC class I molecule
Structural highlights
FunctionHA12_RAT Involved in the presentation of foreign antigens to the immune system. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedAntigenic peptides are loaded onto class I MHC molecules in the endoplasmic reticulum (ER) by a complex consisting of the MHC class I heavy chain, beta(2)-microglobulin, calreticulin, tapasin, Erp57 (ER60) and the transporter associated with antigen processing (TAP). While most mammalian species transport these peptides into the ER via a single allele of TAP, rats have evolved different TAPs, TAP-A and TAP-B, that are present in different inbred strains. Each TAP delivers a different spectrum of peptides and is associated genetically with distinct subsets of MHC class Ia alleles, but the molecular basis for the conservation (or co-evolution) of the two transporter alleles is unknown. We have determined the crystal structures of a representative of each MHC subset, viz RT1-A(a) and RT1-A1(c), in association with high-affinity nonamer peptides. The structures reveal how the chemical properties of the two different rat MHC F-pockets match those of the corresponding C termini of the peptides, corroborating biochemical data on the rates of peptide-MHC complex assembly. An unusual sequence in RT1-A1(c) leads to a major deviation from the highly conserved beta(3)/alpha(1) loop (residues 40-59) conformation in mouse and human MHC class I structures. This loop change contributes to profound changes in the shape of the A-pocket in the peptide-binding groove and may explain the function of RT1-A1(c) as an inhibitory natural killer cell ligand. Crystal structures of two rat MHC class Ia (RT1-A) molecules that are associated differentially with peptide transporter alleles TAP-A and TAP-B.,Rudolph MG, Stevens J, Speir JA, Trowsdale J, Butcher GW, Joly E, Wilson IA J Mol Biol. 2002 Dec 13;324(5):975-90. PMID:12470953[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences | ||||||||||||||||||||
