Ubiquitin and the SCF(Grr1) ubiquitin ligase complex are involved in the signalling pathway activated by external amino acids in Saccharomyces cerevisiae.

In response to external amino acids, the permease-like sensor Ssy1 of Saccharomyces cerevisiae activates a pathway leading to transcriptional induction of several permease genes including AGP1 and PTR2. We previously reported that AGP1 induction requires Grr1, the F-box protein part of the SCF(Grr1) ubiquitin-ligase complex. We show here that ubiquitin, other components of SCF(Grr1) and the ubiquitin-conjugating enzyme Cdc34 are essential for AGP1 and PTR2 induction. This suggests that transduction to these genes of the amino acid signal generated by Ssy1 involves an SCF(Grr1)-catalysed ubiquitination step.