title: Dolichol-linked oligosaccharide selection by the oligosaccharyltransferase in protist and fungal organisms.
abstract: The dolichol-linked oligosaccharide Glc3Man9GlcNAc2-PP-Dol is the in vivo donor substrate synthesized by most eukaryotes for asparagine-linked glycosylation. However, many protist organisms assemble dolichol-linked oligosaccharides that lack glucose residues. We have compared donor substrate utilization by the oligosaccharyltransferase (OST) from Trypanosoma cruzi, Entamoeba histolytica, Trichomonas vaginalis, Cryptococcus neoformans, and Saccharomyces cerevisiae using structurally homogeneous dolichol-linked oligosaccharides as well as a heterogeneous dolichol-linked oligosaccharide library. Our results demonstrate that the OST from diverse organisms utilizes the in vivo oligo saccharide donor in preference to certain larger and/or smaller oligosaccharide donors. Steady-state enzyme kinetic experiments reveal that the binding affinity of the tripeptide acceptor for the protist OST complex is influenced by the structure of the oligosaccharide donor. This rudimentary donor substrate selection mechanism has been refined in fungi and vertebrate organisms by the addition of a second, regulatory dolichol-linked oligosaccharide binding site, the presence of which correlates with acquisition of the SWP1/ribophorin II subunit of the OST complex.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Kelleher
authors.forename: Sulagna
authors.initials: S
authors.lastname: Banerjee
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Cura
authors.forename: John
authors.initials: J
authors.lastname: Samuelson
authors.forename: Reid
authors.initials: R
authors.lastname: Gilmore
mesh_terms: D000818:Animals; D001665:Binding Sites; D003455:Cryptococcus neoformans / Q000201:enzymology; D004286:Dolichols / Q000031:analogs & derivatives* / Q000378:metabolism; D004748:Entamoeba histolytica / Q000201:enzymology; D005656:Fungal Proteins / Q000378:metabolism*; D006602:Hexosyltransferases / Q000378:metabolism*; D007700:Kinetics; D008358:Mannose / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D009844:Oligosaccharides / Q000378:metabolism*; D015800:Protozoan Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013379:Substrate Specificity; D014246:Trichomonas vaginalis / Q000201:enzymology; D014349:Trypanosoma cruzi / Q000201:enzymology
chemical_list: D004286:Dolichols; D005656:Fungal Proteins; C520165:Glc3Man9GlcNAc2-PP-Dol; D008565:Membrane Proteins; D009844:Oligosaccharides; D015800:Protozoan Proteins; D006602:Hexosyltransferases; C025620:dolichyl-diphosphooligosaccharide - protein glycotransferase; D008358:Mannose