Sterol and phospholipid acyl chain alterations in Saccharomyces cerevisiae secretion mutants as a function of temperature stress.

Analyses of free sterol, steryl ester and fatty acid components from yeast secretion mutants indicated that free and esterified sterol remained relatively constant over a growth range of 24 C to 34 C. The saturated fatty acid components (16:0 and 18:0) increased while the unsaturated fatty acids (16:1 and 18:1) decreased as the growth temperature increased. In secretory mutants, fatty acid composition changes are more pronounced than in the wild-type strain. A shift toward increased saturated and decreased unsaturated fatty acid was observed when cells were subjected to a 2-hr temperature upshift to 37 C. Steady-state fluorescence anisotropy data indicated that modifications to the lipid component of yeast plasma membrane produced lipid thermotropic transitions that were 3 C to 6 C higher in yeast cells subjected to thermal stress.