Influence of growth conditions on the composition of the plasma membrane from yeast and on kinetic properties of two membrane functions

Abstract

The influence of different growth conditions on the phospholipid composition and on two membrane functions, the Mg-ATPase and the purine transport system, was investigated. Addition of cholinechloride to the growth medium led to a certain rise in the amount of phosphatidylcholine, whereas supplementation with ethanolamine resulted in a considerably higher portion of phosphatidylethanolamine. When yeast cells were cultured at lower temperatures we found more short-chain fatty acids with a higher content of monounsaturated chains as compared to higher growth temperatures. Addition of paraquat, a herbicide which enhances lipid peroxidation by free radicals, reduced the amount of unsaturated fatty acids without influencing their chain length. The altered membrane composition had no influence on the basic mechanism of interaction between ATPase, MgATP, and free Mg2+ ions. However, several kinetic constants such as Km, Vmax, Ka, and especially Ki were influenced to some extent. Whereas the affinity of the purine transport system to its substrate was not significantly changed by the growth conditions, an effect on Vmax could be seen. Lower growth temperatures clearly led to higher maximal uptake velocities. The presence of paraquat during growth resulted in a considerable decrease of Vmax.

Role of Phospholipid Head Groups in Ethanol Tolerance of Saccharomyces cerevisiae

“…There are reports suggesting that an increased ratio of anionic :zwitterionic phospholipids can affect ethanol tolerance (Clark 8c Beard, 1979;Bohin 8z Lubochinsky, 1982). It has also been suggested that the phospholipid head group could modify the effect of ethanol on plasma membrane ATPase activity (Stadtlander et al, 1982). Based on H+-flux measurements, our data do suggest that in PS-enriched cells, H+-translocating activity of ATPase becomes less sensitive to ethanol as compared to wild-type, PC-or PE-enriched cells (Fig.…”

Lipids as modulators of ethanol tolerance in yeast

“…Employing amino acid transport, H + flux and fermentative capability as indices of ethanol tolerance, PS-enriched cells were found to be ethanol resistant compared to PC-or PE-enriched cells. Such an effect of altered head group ratio of phospholipids could be attributed to its ability to modify plasma membrane H ÷-ATPase activity (Stadtlander et al 1982), which in turn combats the effect of ethanol via its capability to extrude protons. Although an enhanced ratio of anion:zwitterion has been reported to increase ethanol tolerance in E. coli (Clark and Beard 1979) and Bacillus subtilis (Bohin and Lubochinsky 1982), its importance in higher organisms has been realized only recently (Hoek and Taraschi 1988).…”