ISSN:
1617-4623
Keywords:
Key words GMP kinase
;
GDP-mannose synthesis
;
N-glycosylation
;
Mannose outer chain elongation
;
Saccharomyces cerevisiae
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004380050591
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