Ardiccioni, ChiaraClarke, Oliver BTomasek, DavidIssa, Habon Avon Alpen, Desiree CPond, Heather LBanerjee, SurajitRajashankar, Kanagalaghatta RLiu, QunGuan, ZiqiangLi, ChijunKloss, BrianBruni, RenatoKloppmann, EddaRost, BurkhardManzini, M ChiaraShapiro, LawrenceMancia, Filippo2016-02-012016-01-05https://hdl.handle.net/10161/11564The attachment of a sugar to a hydrophobic polyisoprenyl carrier is the first step for all extracellular glycosylation processes. The enzymes that perform these reactions, polyisoprenyl-glycosyltransferases (PI-GTs) include dolichol phosphate mannose synthase (DPMS), which generates the mannose donor for glycosylation in the endoplasmic reticulum. Here we report the 3.0 Å resolution crystal structure of GtrB, a glucose-specific PI-GT from Synechocystis, showing a tetramer in which each protomer contributes two helices to a membrane-spanning bundle. The active site is 15 Å from the membrane, raising the question of how water-soluble and membrane-embedded substrates are brought into apposition for catalysis. A conserved juxtamembrane domain harbours disease mutations, which compromised activity in GtrB in vitro and in human DPM1 tested in zebrafish. We hypothesize a role of this domain in shielding the polyisoprenyl-phosphate for transport to the active site. Our results reveal the basis of PI-GT function, and provide a potential molecular explanation for DPM1-related disease.AnimalsAnimals, Genetically ModifiedGene Expression Regulation, BacterialGene Expression Regulation, EnzymologicGlycosyltransferasesHumansMannosyltransferasesModels, MolecularProtein ConformationSynechocystisZebrafishJournal article2041-1723