title: Two yeast mutations in glucosylation steps of the asparagine glycosylation pathway.
abstract: Two complementing mutations in lipid-linked oligosaccharide biosynthesis have been isolated following a [3H]mannose suicide enrichment. Rather than making the wild type precursor oligosaccharide, Glc3man9Glc-NA2-P-P-dolichol, the mutants, alg5-1 and alg6-1, accumulate Man9GlcNAc2-P-P-dolichol as their largest lipid-linked oligosaccharide in vivo and in vitro. When UDP-[3H]Glc was added to microsomal membranes of each mutant, neither could elongate Man9GlcNAc2-P-P-dolichol and only alg6-1 could synthesize dolichol-phosphoglucose. When dolicholphospho[3H]glucose was added to microsomes from alg5-1, alg6-1, or the parental strain, only alg5-1 and the parental strain made glucosylated lipid-linked oligosaccharides. These results indicate that alg5-1 cells are unable to synthesize dolichol phosphoglucose while alg6-1 cells are unable to transfer glucose from dolichol phosphoglucose to the unglucosylated lipid-linked oligosaccharide. We also present evidence that both mutants transfer Man9GlcNAc2 to protein.
mesh_terms: D000118:Acetylglucosaminidase / Q000378:metabolism; D001216:Asparagine / Q000378:metabolism*; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D009154:Mutation; D011103:Polyisoprenyl Phosphate Monosaccharides / Q000378:metabolism; D011104:Polyisoprenyl Phosphate Oligosaccharides / Q000096:biosynthesis*; D011105:Polyisoprenyl Phosphate Sugars / Q000096:biosynthesis*; D012441:Saccharomyces cerevisiae / Q000235:genetics*
chemical_list: D011103:Polyisoprenyl Phosphate Monosaccharides; D011104:Polyisoprenyl Phosphate Oligosaccharides; D011105:Polyisoprenyl Phosphate Sugars; C024962:dolichyl diphosphate oligosaccharides; C002968:dolichol-D-glucosylmonophosphate; D001216:Asparagine; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase