HLA-A

MHC class I, A (heterodimer)
Illustration of HLA-A
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Protein type		Cell surface receptor
Function		Peptide presentation for immune recognition
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Subunit name	Gene	Chromosomal locus
α	HLA-A	Chromosome 6p21.3
β2M	B2M	Chromosome 15q22

HLA-A
Available structures PDB Human UniProt search: PDBe RCSB List of PDB id codes 2XPG, 3RL1, 3RL2,%%s2BCK, 3I6L, 3NFN, 3QZW, 3VXM, 3VXN, 3VXO, 3VXP, 3VXR, 3VXS, 3VXU, 3W0W, 3WL9, 3WLB, 4F7M, 4F7P, 4F7T, 4WU5, 4WU7, 5HGA, 5HGD, 5HGB, 5HGH,%%s1Q94, 1QVO, 1X7Q, 2HN7, 4MJ5, 4MJ6, 4N8V, 4UQ2,%%s1W72, 3BO8, 4NQV, 4NQX, 5BRZ, 5BS0,%%s1AKJ, 1AO7, 1AQD, 1B0G, 1B0R, 1BD2, 1DUY, 1DUZ, 1EEY, 1EEZ, 1HHG, 1HHH, 1HHI, 1HHJ, 1HHK, 1HLA, 1I1F, 1I1Y, 1I4F, 1I7R, 1I7T, 1I7U, 1IM3, 1JF1, 1JHT, 1LP9, 1OGA, 1P7Q, 1QEW, 1QR1, 1QRN, 1QSE, 1QSF, 1S8D, 1S9W, 1S9X, 1S9Y, 1T1W, 1T1X, 1T1Y, 1T1Z, 1T20, 1T21, 1T22, 1TVB, 1TVH, 2AV1, 2AV7, 2BNQ, 2BNR, 2C7U, 2CLR, 2F53, 2F54, 2GIT, 2GJ6, 2GT9, 2GTW, 2GTZ, 2GUO, 2J8U, 2JCC, 2P5E, 2P5W, 2PYE, 2UWE, 2V2W, 2V2X, 2VLJ, 2VLK, 2VLL, 2VLR, 2X4N, 2X4O, 2X4P, 2X4Q, 2X4R, 2X4S, 2X4T, 2X4U, 2X70, 3BGM, 3BH8, 3BH9, 3BHB, 3D25, 3D39, 3D3V, 3FQN, 3FQR, 3FQT, 3FQU, 3FQW, 3FQX, 3FT2, 3FT3, 3FT4, 3GIV, 3GJF, 3GSN, 3GSO, 3GSQ, 3GSR, 3GSU, 3GSV, 3GSW, 3GSX, 3H7B, 3H9H, 3H9S, 3HAE, 3HLA, 3HPJ, 3I6G, 3I6K, 3IXA, 3KLA, 3MGO, 3MGT, 3MR9, 3MRB, 3MRC, 3MRD, 3MRF, 3MRG, 3MRH, 3MRI, 3MRJ, 3MRK, 3MRL, 3MRM, 3MRN, 3MRO, 3MRP, 3MRQ, 3MRR, 3MYJ, 3O3A, 3O3B, 3O3D, 3O3E, 3PWJ, 3PWL, 3PWN, 3PWP, 3QDG, 3QDJ, 3QDM, 3QEQ, 3QFD, 3QFJ, 3REW, 3TO2, 3UTQ, 3UTS, 3UTT, 3V5D, 3V5H, 3V5K, 4E5X, 4EMZ, 4EN2, 4EUP, 4FTV, 4GKN, 4GKS, 4I4W, 4JFD, 4JFE, 4JFF, 4JFO, 4JFP, 4JFQ, 4K7F, 4L29, 4L3C, 4L3E, 4MNQ, 4NNX, 4NNY, 4NO0, 4NO2, 4NO3, 4NO5, 4OV5, 4QOK, 4U6X, 4U6Y, 4UQ3, 4WJ5, 4WUU, 5EU3, 5EU5, 5EU4, 5D2L, 5D2N, 5EU6, 5HHQ, 5HHO, 5HHM, 5C09, 5C0F, 5E9D, 5C0G, 5C0A, 4ZEZ, 5C0I, 5D9S, 5HYJ, 5C0H, 5C0J, 5C0E, 5C0C, 5C0B, 5C07, 5C0D, 5C08, 5HHN,%%s1HSB, 1TMC, 2HLA, 4HWZ, 4HX1, 4I48
Identifiers
Aliases	HLA-A, Aw-33, Aw-74, major histocompatibility complex, class I, A, HLA-A11, HLA-A33, HLA-DQB1, HLA-DRB1
External IDs	OMIM: 142800 MGI: 95928 HomoloGene: 128352 GeneCards: HLA-A
Gene ontology Molecular function • beta-2-microglobulin binding • TAP binding • peptide antigen binding • protein binding • T cell receptor binding • receptor binding • RNA binding Cellular component • integral component of membrane • phagocytic vesicle membrane • Golgi apparatus • early endosome membrane • Golgi membrane • plasma membrane • integral component of plasma membrane • cell surface • endoplasmic reticulum • ER to Golgi transport vesicle membrane • integral component of lumenal side of endoplasmic reticulum membrane • MHC class I protein complex • membrane • recycling endosome membrane • extracellular exosome • Golgi medial cisterna • endoplasmic reticulum exit site • secretory granule membrane Biological process • antigen processing and presentation • antigen processing and presentation of exogenous peptide antigen via MHC class I, TAP-dependent • interferon-gamma-mediated signaling pathway • immune system process • antigen processing and presentation of exogenous peptide antigen via MHC class I, TAP-independent • type I interferon signaling pathway • regulation of immune response • viral process • immune response • antigen processing and presentation of peptide antigen via MHC class I • protection from natural killer cell mediated cytotoxicity • positive regulation of T cell mediated cytotoxicity • detection of bacterium • antibacterial humoral response • positive regulation of memory T cell activation • positive regulation of interferon-gamma production • regulation of defense response to virus by virus • antigen processing and presentation of endogenous peptide antigen via MHC class I • positive regulation of CD8-positive, alpha-beta T cell activation • positive regulation of T cell cytokine production • positive regulation of CD8-positive, alpha-beta T cell proliferation • antigen processing and presentation of endogenous peptide antigen via MHC class I via ER pathway, TAP-independent • defense response to Gram-positive bacterium • neutrophil degranulation Sources:Amigo / QuickGO
Orthologs
Species	Human	Mouse
Entrez	3105	15006
Ensembl	n/a	ENSMUSG00000079507
UniProt	P04439 P05534 P13746 P16188 P30443 P30455 Q09160 P01892 P30450 P18462 P16189 P16190 P10314 P30457 P30453 P30459 P01891 P30456 P10316 P30512 P30447	n/a
RefSeq (mRNA)	NM_001242758 NM_002116	NM_010390
RefSeq (protein)	NP_002107.3 NP_001229687.1	n/a
Location (UCSC)	Chr 6: 29.94 – 29.95 Mb	Chr 17: 35.32 – 35.33 Mb
PubMed search

HLA-A is a group of human leukocyte antigens (HLA) that are coded for by the HLA-A locus, which is located at human chromosome 6p21.3. HLA is a (MHC) antigen specific to humans. HLA-A is one of three major types of human MHC class I cell surface receptors. The others are HLA-B and HLA-C. The receptor is a heterodimer, and is composed of a heavy α chain and smaller β chain. The α chain is encoded by a variant HLA-A gene, and the β chain (β₂-microglobulin) is an invariant β₂ microglobulin molecule. The β₂ microglobulin protein is coded for by a separate region of the human genome.

MHC Class I molecules such as HLA-A are part of a process that presents short polypeptides to the immune system. These polypeptides are typically 7-11 amino acids in length and originate from proteins being expressed by the cell. There are two classes of polypeptide that can be presented by an HLA protein: those that are supposed to be expressed by the cell (self) and those of foreign derivation (non-self). Under normal conditions cytotoxic T cells, which normally patrol the body in the blood, "read" the peptide presented by the complex. T cells, if functioning properly, only bind to non-self peptides. If binding occurs, a series of events is initiated culminating in cell death via apoptosis. In this manner, the human body eliminates any cells infected by a virus or expressing proteins they shouldn't be (e.g. cancerous cells).

For humans, as in most mammalian populations, MHC Class I molecules are extremely variable in their primary structure, and HLA-A is ranked among the genes in humans with the fastest-evolving coding sequence. As of December 2013, there are 2432 known HLA-A alleles coding for 1740 active proteins and 117 null proteins. This level of variation on MHC Class I is the primary cause of transplant rejection, as random transplantation between donor and host is unlikely to result in a matching of HLA-A, B or C antigens. Evolutionary biologists also believe that the wide variation in HLAs is a result of a balancing act between conflicting pathogenic pressures. Greater variety of HLAs decreases the probability that the entire population will be wiped out by a single pathogen as certain individuals will be highly resistant to each pathogen. The effect of HLA-A variation on HIV/AIDS progression is discussed below.

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Wikipedia