UGA4 GENE-EXPRESSION IN SACCHAROMYCES-CEREVISIAE DEPENDS ON CELL-GROWTH CONDITIONS

In the yeast Saccharomyces cerevisiae, gamma-aminobutyric acid (GABA) transport is mediated by three permeases: the general amino acid perme ase GAP I, the proline permease PUT4 and the specific GABA permease UG A4. Expression of UGA4 gene is induced in the presence of GABA. We sta rted a comparative study about UGA4 gene induction in cells grown on d ifferent culture media. Results presented here indicate that under cer tain growth conditions UGA4 permease is constitutive. Therefore, we de monstrate that in S. cerevisiae the UGA4 gene expression depends on ce ll growth conditions and that its synthesis not always depends on the presence of GABA.