Plasma-membrane phospholipid unsaturation affects expression of the general amino-acid permease in Saccharomyces cerevisiae Y185.

Saccharomyces cerevisiae Y185, enriched in linoleyl residues and incubated for up to 4 h in derepression buffer, more rapidly acquired general amino-acid permease (GAP) activity, as measured by the rate of accumulation of L-alanine, compared with organisms enriched in oleyl residues. A GAP-less mutant incubated under the same conditions did not acquire further L-alanine-accumulating ability, irrespective of the nature of the fatty-acyl enrichment. During derepression, KT values for the GAP were virtually identical irrespective of the fatty-acyl enrichment, but Vmax values were greater for linoleyl residue-enriched organisms, particularly after 1 h in derepression buffer. During incubation in derepression buffer, organisms with either fatty-acyl enrichment did not differ in the size of the amino-N pool, the concentration of L-alanine in that pool, rates of protein synthesis and glucose fermentation, or rate and extent of incorporation of label from H2 32PO-4. Under conditions used to measure rates of L-alanine accumulation, organisms with either enrichment showed no evidence of metabolism of accumulated L-alanine.