Effect of fatty acid supplementation on thermotropic behavior of membrane lipids and leucine transport in Saccharomyces cerevisiae.

An unsaturated fatty acid-requiring mutant (KD 115) of Saccharomyces cerevisiae shows altered phospholipid composition, transport behavior, and physical properties of membrane lipids when grown in the presence of different cis- and trans-unsaturated fatty acids. There is an increase in phosphatidyl ethanolamine content and a concomitant decrease in phosphatidyl choline content in the cells supplemented with trans-unsaturated fatty acids. The affinity for uptake of L-leucine is higher in the cis-unsaturated fatty acid-supplemented cells compared with the trans-unsaturated fatty acid-supplemented cells. The temperature-dependence of L-leucine uptake bears a reasonably good correlation with the thermotropic behavior of the membrane lipids as studied by the steady-state fluorescence polarization technique. The present findings are discussed in light of the importance of the lipid environment in modulating membrane-associated functions.