Transcriptional and posttranslational regulation of the general amino acid permease of Saccharomyces cerevisiae.

The cellular level and activity of the general amino acid permease, the product of the GAP1 gene of Saccharomyces cerevisiae, are regulated at the level of transcription by two systems, the products of URE2/GLN3 and NIL1 in response to the nitrogen sources of the growth medium and inactivation in response to the presence of glutamine or glutamate. Active permease is phosphorylated. The addition of glutamine causes rapid dephosphorylation and inactivation of the permease with the same kinetics, which is followed by slower disappearance of the protein. These results suggest that inactivation of the permease results from its dephosphorylation.