Functional characterization of Ost3p. Loss of the 34-kD subunit of the Saccharomyces cerevisiae oligosaccharyltransferase results in biased underglycosylation of acceptor substrates
UMass Chan Affiliations
Department of Biochemistry and Molecular BiologyDocument Type
Journal ArticlePublication Date
1995-08-01Keywords
Amino Acid SequenceBase Sequence
Carbohydrate Sequence
Crosses, Genetic
Endoplasmic Reticulum
Genes, Fungal
Genomic Library
Glycosylation
*Hexosyltransferases
Membrane Glycoproteins
*Membrane Proteins
Molecular Sequence Data
Mutagenesis
Oligosaccharides
Precipitin Tests
Protein Conformation
Protein Processing, Post-Translational
Saccharomyces cerevisiae
Sequence Analysis
Transferases
Biochemistry
Cell Biology
Molecular Biology
Metadata
Show full item recordAbstract
Within the lumen of the rough endoplasmic reticulum, oligosaccharyltransferase catalyzes the en bloc transfer of a high mannose oligosaccharide moiety from the lipid-linked oligosaccharide donor to asparagine acceptor sites in nascent polypeptides. The Saccharomyces cerevisiae oligosaccharyltransferase was purified as a heteroligomeric complex consisting of six subunits (alpha-zeta) having apparent molecular masses of 64 kD (Ost1p), 45 kD (Wbp1p), 34 kD, 30 kD (Swp1p), 16 kD, and 9 kD. Here we report a structural and functional characterization of Ost3p which corresponds to the 34-kD gamma-subunit of the oligosaccharyltransferase. Unlike Ost1p, Wbp1p, and Swp1p, expression of Ost3p is not essential for viability of yeast. Instead, ost3 null mutant yeast grow at wild-type rates on solid or in liquid media irrespective of culture temperature. Nonetheless, detergent extracts prepared from ost3 null mutant membranes are twofold less active than extracts prepared from wild-type membranes in an in vitro oligosaccharyltransferase assay. Furthermore, loss of Ost3p is accompanied by significant underglycosylation of soluble and membrane-bound glycoproteins in vivo. Compared to the previously characterized ost1-1 mutant in the oligosaccharyltransferase, and the alg5 mutant in the oligosaccharide assembly pathway, ost3 null mutant yeast appear to be selectively impaired in the glycosylation of several membrane glycoproteins. The latter observation suggests that Ost3p may enhance oligosaccharide transfer in vivo to a subset of acceptor substrates.Source
J Cell Biol. 1995 Aug;130(3):567-77.Permanent Link to this Item
http://hdl.handle.net/20.500.14038/42615PubMed ID
7622558Related Resources
Link to Article in PubMedCollections
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