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Crystal Structure of Human Galactosyltransferase (GTB) Complexed with Lactose
Structural highlights
FunctionBGAT_HUMAN This protein is the basis of the ABO blood group system. The histo-blood group ABO involves three carbohydrate antigens: A, B, and H. A, B, and AB individuals express a glycosyltransferase activity that converts the H antigen to the A antigen (by addition of UDP-GalNAc) or to the B antigen (by addition of UDP-Gal), whereas O individuals lack such activity. 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 PubMedThe human ABO(H) blood group A and B antigens are generated by the homologous glycosyltransferases A (GTA) and B (GTB), which add the monosaccharides GalNAc and Gal, respectively, to the cell-surface H antigens. In the first comprehensive structural study of the recognition by a glycosyltransferase of a panel of substrates corresponding to acceptor fragments, 14 high resolution crystal structures of GTA and GTB have been determined in the presence of oligosaccharides corresponding to different segments of the type I (alpha-l-Fucp-(1-->2)-beta-D-Galp-(1-->3)-beta-D-GlcNAcp-OR, where R is a glycoprotein or glycolipid in natural acceptors) and type II (alpha-l-Fucp-(1-->2)-beta-D-Galp-(1-->4)-beta-d-GlcNAcp-OR) H antigen trisaccharides. GTA and GTB differ in only four "critical" amino acid residues (Arg/Gly-176, Gly/Ser-235, Leu/Met-266, and Gly/Ala-268). As these enzymes both utilize the H antigen acceptors, the four critical residues had been thought to be involved strictly in donor recognition; however, we now report that acceptor binding and subsequent transfer are significantly influenced by two of these residues: Gly/Ser-235 and Leu/Met-266. Furthermore, these structures show that acceptor recognition is dominated by the central Gal residue despite the fact that the L-Fuc residue is required for efficient catalysis and give direct insight into the design of model inhibitors for GTA and GTB. Differential recognition of the type I and II H antigen acceptors by the human ABO(H) blood group A and B glycosyltransferases.,Letts JA, Rose NL, Fang YR, Barry CH, Borisova SN, Seto NO, Palcic MM, Evans SV J Biol Chem. 2006 Feb 10;281(6):3625-32. Epub 2005 Dec 2. PMID:16326711[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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