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Ordered assembly of the asymmetrically branched lipid-linked oligosaccharide in the endoplasmic reticulum is ensured by the substrate specificity of the individual glycosyltransferases


Burda, P; Jakob, C A; Beinhauer, J; Hegemann, J H; Aebi, M (1999). Ordered assembly of the asymmetrically branched lipid-linked oligosaccharide in the endoplasmic reticulum is ensured by the substrate specificity of the individual glycosyltransferases. Glycobiology, 9(6):617-625.

Abstract

The assembly of the lipid-linked core oligosaccharide Glc3Man9GlcNAc2, the substrate for N-linked glycosylation of proteins in the endoplasmic reticulum (ER), is catalyzed by different glycosyltransferases located at the membrane of the ER. We report on the identification and characterization of the ALG12 locus encoding a novel mannosyltransferase responsible for the addition of the α-1,6 mannose to dolichollinked Man7GlcNAc2. The biosynthesis of the highly branched oligosaccharide follows an ordered pathway which ensures that only completely assembled oligosaccharide is transferred from the lipid anchor to proteins. Using the combination of mutant strains affected in the assembly pathway of lipid-linked oligosaccharides and overexpression of distinct glycosyltransferases, we were able to define the substrate specificities of the transferases that are critical for branching. Our results demonstrate that branched oligosaccharide structures can be specifically recognized by the ER glycosyltransferases. This substrate specificity of the different transferases explains the ordered assembly of the complex structure of lipid-linked Glc3Man9GlcNAc2 in the endoplasmic reticulum

Abstract

The assembly of the lipid-linked core oligosaccharide Glc3Man9GlcNAc2, the substrate for N-linked glycosylation of proteins in the endoplasmic reticulum (ER), is catalyzed by different glycosyltransferases located at the membrane of the ER. We report on the identification and characterization of the ALG12 locus encoding a novel mannosyltransferase responsible for the addition of the α-1,6 mannose to dolichollinked Man7GlcNAc2. The biosynthesis of the highly branched oligosaccharide follows an ordered pathway which ensures that only completely assembled oligosaccharide is transferred from the lipid anchor to proteins. Using the combination of mutant strains affected in the assembly pathway of lipid-linked oligosaccharides and overexpression of distinct glycosyltransferases, we were able to define the substrate specificities of the transferases that are critical for branching. Our results demonstrate that branched oligosaccharide structures can be specifically recognized by the ER glycosyltransferases. This substrate specificity of the different transferases explains the ordered assembly of the complex structure of lipid-linked Glc3Man9GlcNAc2 in the endoplasmic reticulum

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Item Type:Journal Article, refereed, original work
Communities & Collections:National licences > 142-005
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:1 June 1999
Deposited On:20 Sep 2018 14:12
Last Modified:25 Apr 2019 20:00
Publisher:Oxford University Press
ISSN:0959-6658
OA Status:Green
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1093/glycob/9.6.617
Related URLs:https://www.swissbib.ch/Search/Results?lookfor=nationallicenceoxford101093glycob96617 (Library Catalogue)

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