GYPA
Glycophorins A (GYPA) and B (GYPB) are major sialoglycoproteins of the human erythrocyte membrane which bear the antigenic determinants for the MN and Ss blood groups. In addition to the M or N and S or s antigens that commonly occur in all populations, about 40 related variant phenotypes have been identified. These variants include all the variants of the Miltenberger complex and several isoforms of Sta, as well as Dantu, Sat, He, Mg, and deletion variants Ena, S-s-U- and Mk. Most of the variants are the result of gene recombinations between GYPA and GYPB. [provided by RefSeq, Jul 2008]
Full Name
Glycophorin A (MNS Blood Group)
Function
Glycophorin A is the major intrinsic membrane protein of the erythrocyte. The N-terminal glycosylated segment, which lies outside the erythrocyte membrane, has MN blood group receptors. Appears to be important for the function of SLC4A1 and is required for high activity of SLC4A1. May be involved in translocation of SLC4A1 to the plasma membrane. Is a receptor for influenza virus. Is a receptor for Plasmodium falciparum erythrocyte-binding antigen 175 (EBA-175); binding of EBA-175 is dependent on sialic acid residues of the O-linked glycans. Appears to be a receptor for Hepatitis A virus (HAV).
Cellular Location
Cell membrane. Appears to be colocalized with SLC4A1.
Topology
Extracellular: 20-91
Helical: 92-114
Cytoplasmic: 115-150
PTM
The major O-linked glycan are NeuAc-alpha-2-3-Gal-beta-1-3-[NeuAc-alpha-2-6]-GalNAcOH (about 78 %) and NeuAc-alpha-2-3-Gal-beta-1-3-GalNAcOH (17 %). Minor O-glycans (5 %) include NeuAc-alpha-2-3-Gal-beta-1-3-[NeuAc-alpha-2-6]-GalNAcOH NeuAc-alpha-2-8-NeuAc-alpha-2-3-Gal-beta-1-3-GalNAcOH. About 1% of all O-linked glycans carry blood group A, B and H determinants. They derive from a type-2 precursor core structure, Gal-beta-(1,3)-GlcNAc-beta-1-R, and the antigens are synthesized by addition of fucose (H antigen-specific) and then N-acetylgalactosamine (A antigen-specific) or galactose (B antigen-specific). Specifically O-linked-glycans are NeuAc-alpha-2-3-Gal-beta-1-3-GalNAcOH-6-1-GlcNAc-beta-4-1-[Fuc-alpha-1-2]-Gal-beta-3-1-GalNAc-alpha (about 1%, B antigen-specific) and NeuAc-alpha-2-3-Gal-beta-1-3-GalNAcOH-6-1-GlcNAc-beta-4-1-[Fuc-alpha-1-2]-Gal-beta (1 %, O antigen-, A antigen- and B antigen-specific).
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