[Term] id: PR:000001818 name: MHC class I histocompatibility antigen alpha chain def: "A protein with core architecture consisting of an extracellular region with Class I Histocompatibility antigen, domains alpha 1 and alpha two (Pfam:PF00129) and an Immunoglobulin C1-set domain (Pfam:PF07654), a single-pass transmembrane region, and a cytoplasmic region containing the MHC_I C-terminus (Pfam:PF06623)." [PRO:WCB, Wikipedia:Human_leukocyte_antigen] comment: Category=family. Note: There are three major and three minor class I MHC (major histocompatability complex) alpha chain genes in human. Designations for the MHC complex loci are species specific: HLA (human leukocyte antigen) in human, H-2 in mouse. MHC class I loci are characterized by large numbers of allelic variants. Human and mouse genes for MHC class I histocompatibility antigen alpha chains represent independent lineage-specific expansions. MHC class I histocompatibility antigen alpha chains associate with beta-2 microglobulin to form the heterodimeric MHC antigens. synonym: "MHCcIalpha" EXACT PRO-short-label [PRO:DAN] is_a: PR:000000001 ! protein