A defect in GTP synthesis affects mannose outer chain elongation in Saccharomyces cerevisiae

A defect in GTP synthesis affects mannose outer chain elongation in Saccharomyces cerevisiae We have found that yeast mutants that are defective in mannose outer chain elongation of N-linked glycoproteins show higher cell wall porosity than normal cells, and are hypersensitive to antibiotics with a large molecular weight; such as neomycin and geneticin. Wild-type yeast cells also showed enhanced sensitivity to neomycin in the presence of tunicamycin, an inhibitor of N-glycosylation, suggesting that the extent of N-glycosylation may affect the sensitivity of yeast cells to drugs and that sensitivity to neomycin may be an effective method for screening for yeast mutants defective in N-glycosylation. Pursuing this logic, we isolated neomycin-sensitive yeast mutants and screened them for defects in N-glycosylation. The neomycin-sensitive, N-glycosylation-defective mutants fell into 15 complementation groups including alleles of the previously isolated temperature-sensitive nes mutants nes10, nes17, and nes25. Gene cloning revealed that NES10 was identical to SEC20, which is involved in ER-Golgi protein transport. NES17 was identical to ALG1, which encodes a β-1,4-mannosyltransferase present in the ER. MSN17, a multicopy suppressor of nes17/alg1, was also isolated and found to be an allele of PSA1, which is involved in GDP-mannose synthesis. NES25 was identical to GUK1, which encodes a GMP kinase. Overexpression of MSN17 increased the GDP-mannose level in a wild-type strain by about threefold, and guk1 decreased the GDP-mannose level to one-fourth, suggesting a close relationship between GTP metabolism and mannose outer chain elongation; the link is presumably provided by the process of GDP-mannose transport in the Golgi membranes. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Molecular Genetics and Genomics Springer Journals

A defect in GTP synthesis affects mannose outer chain elongation in Saccharomyces cerevisiae

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Publisher
Springer Journals
Copyright
Copyright © 1997 by Springer-Verlag Berlin Heidelberg
Subject
Life Sciences; Cell Biology; Biochemistry, general; Microbial Genetics and Genomics; Plant Genetics & Genomics; Animal Genetics and Genomics
ISSN
1617-4615
eISSN
1432-1874
DOI
10.1007/s004380050591
Publisher site
See Article on Publisher Site

Abstract

We have found that yeast mutants that are defective in mannose outer chain elongation of N-linked glycoproteins show higher cell wall porosity than normal cells, and are hypersensitive to antibiotics with a large molecular weight; such as neomycin and geneticin. Wild-type yeast cells also showed enhanced sensitivity to neomycin in the presence of tunicamycin, an inhibitor of N-glycosylation, suggesting that the extent of N-glycosylation may affect the sensitivity of yeast cells to drugs and that sensitivity to neomycin may be an effective method for screening for yeast mutants defective in N-glycosylation. Pursuing this logic, we isolated neomycin-sensitive yeast mutants and screened them for defects in N-glycosylation. The neomycin-sensitive, N-glycosylation-defective mutants fell into 15 complementation groups including alleles of the previously isolated temperature-sensitive nes mutants nes10, nes17, and nes25. Gene cloning revealed that NES10 was identical to SEC20, which is involved in ER-Golgi protein transport. NES17 was identical to ALG1, which encodes a β-1,4-mannosyltransferase present in the ER. MSN17, a multicopy suppressor of nes17/alg1, was also isolated and found to be an allele of PSA1, which is involved in GDP-mannose synthesis. NES25 was identical to GUK1, which encodes a GMP kinase. Overexpression of MSN17 increased the GDP-mannose level in a wild-type strain by about threefold, and guk1 decreased the GDP-mannose level to one-fourth, suggesting a close relationship between GTP metabolism and mannose outer chain elongation; the link is presumably provided by the process of GDP-mannose transport in the Golgi membranes.

Journal

Molecular Genetics and GenomicsSpringer Journals

Published: Nov 20, 1997

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