The ALG10 locus of Saccharomyces cerevisiae encodes the alpha-1,2 glucosyltransferase of the endoplasmic reticulum: the terminal glucose of the lipid-linked oligosaccharide is required for efficient N-linked glycosylation.
The biosynthesis of the lipid-linked oligosaccharide substrate for N-linked protein glycosylation follows a highly conserved pathway at the membrane of the endoplasmic reticulum. Based on the synthetic growth defect in combination with a reduced oligosaccharyltransferase activity (wbp1), we have identified alg10 mutant strains which accumulate lipid-linked Glc2Man9GlcNAc2. We cloned the ... corresponding wild-type gene and show in a novel in vitro assay that Alg10p is a dolichyl-phosphoglucose-dependent glucosyltransferase which adds the terminal alpha-1,2 glucose to the lipid-linked Glc2Man9GlcNAc2 oligosaccharide. Hypoglycosylation of secreted proteins in alg10 deletion strains demonstrates that the terminal alpha-1,2-linked glucose residue is a key element in substrate recognition by the oligosaccharyltransferase. This ensures that primarily completely assembled oligosaccharide is transferred to protein.
Mesh Terms:
Carbohydrate Sequence, Endoplasmic Reticulum, Glucosyltransferases, Glycosylation, Hexosyltransferases, Intracellular Membranes, Kinetics, Membrane Proteins, Microsomes, Molecular Sequence Data, Oligosaccharides, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Transferases
Carbohydrate Sequence, Endoplasmic Reticulum, Glucosyltransferases, Glycosylation, Hexosyltransferases, Intracellular Membranes, Kinetics, Membrane Proteins, Microsomes, Molecular Sequence Data, Oligosaccharides, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Transferases
Glycobiology
Date: May. 01, 1998
PubMed ID: 9597543
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