title: Requirement for a second sterol biosynthetic mutation for viability of a sterol C-14 demethylation defect in Saccharomyces cerevisiae.
abstract: Genetic analysis of a nystatin-resistant sterol mutant (strain JR4) of Saccharomyces cerevisiae defective in C-14 demethylation revealed the presence of a second mutation in 5,6-desaturation. It appeared from complementation tests that a defect in delta 5-desaturase enzyme activity was required for the viability of the C-14 demethylation mutant. Growth studies with a sterol auxotrophic strain indicated that the major sterol of strain JR4, 14 alpha-methyl-ergosta-8,24(28)-dien-3 beta-ol, could satisfy "bulk" membrane requirements but not the second, structurally specific, sterol function that we defined previously (Rodriguez et al., Biochem. Biophys. Res. Commun. 106:435-441, 1982). Leakiness in the sterol mutations in strain JR4 provided a small amount of ergosterol which could satisfy this second function.
mesh_terms: D003577:Cytochrome P-450 Enzyme System; D000090943:Delta-5 Fatty Acid Desaturase; D044943:Fatty Acid Desaturases / Q000235:genetics*; D007700:Kinetics; D013058:Mass Spectrometry; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D058886:Sterol 14-Demethylase; D013261:Sterols / Q000096:biosynthesis*
chemical_list: D000090943:Delta-5 Fatty Acid Desaturase; D013261:Sterols; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase; D044943:Fatty Acid Desaturases