INCORPORATION OF EXTRACELLULAR PHOSPHOLIPIDS AND THEIR EFFECT ON THE GROWTH AND LIPID-METABOLISM OF THE SACCHAROMYCES-CEREVISIAE CHO1 PSS MUTANT/

The chollpss mutant of Saccharomyces cerevisiae, which is auxotrophic for choline or ethanolamine because of the deficiency in phosphatidyls erine synthesis, grew in the presence of 0.05 mM phosphatidylcholine ( PC) with octanoic acids (diC8PC) or decanoic acids (diC10PC), but not in the presence of PC with longer acyl residues. It did not grow in th e presence of the soluble hydrolytic products of PC, phosphorylcholine or glycerophosphorylcholine, at comparable concentrations. Addition o f 10 mM hemicholinium-3, a choline transport inhibitor, or disruption of the CTR gene, which encodes a choline transporter, inhibited the gr owth of the chollpss mutant in the presence of choline, but not in the presence of 0.1 mM diC8PC. Under diC8PC-supported growth conditions, octanoic acid was barely detectable in the cellular phospholipid fract ion, but was recovered in the culture medium as the free acid, and the phosphatidylethanolamine (PE) content was low in comparison to the ch oline-supported conditions. These results suggest that PCs with short acyl residues were taken up by the chollpss mutant and remodeled as th ey were used, and that PCs with short acyl residues do not inhibit con version of PE to PC. The current results provide a new direction in th e analysis of intracellular phospholipid movement and metabolism in ye ast. (C) 1998 Elsevier Science B.V. All rights reserved.