PMID:9614172

Citation	Springael, JY and André, B (1998) Nitrogen-regulated ubiquitination of the Gap1 permease of Saccharomyces cerevisiae. Mol. Biol. Cell 9:1253-63
Abstract	Addition of ammonium ions to yeast cells growing on proline as the sole nitrogen source induces rapid inactivation and degradation of the general amino acid permease Gap1 through a process requiring the Npi1/Rsp5 ubiquitin (Ub) ligase. In this study, we show that NH4+ induces endocytosis of Gap1, which is then delivered into the vacuole where it is degraded. This down-regulation is accompanied by increased conversion of Gap1 to ubiquitinated forms. Ubiquitination and subsequent degradation of Gap1 are impaired in the npi1 strain. In this mutant, the amount of Npi1/Rsp5 Ub ligase is reduced >10-fold compared with wild-type cells. The C-terminal tail of Gap1 contains sequences, including a di-leucine motif, which are required for NH4+-induced internalization and degradation of the permease. We show here that mutant Gap1 permeases affected in these sequences still bind Ub. Furthermore, we provide evidence that only a small fraction of Gap1 is modified by Ub after addition of NH4+ to mutants defective in endocytosis.
Links	PubMed PMC25348
Keywords	Amino Acid Sequence; Amino Acid Transport Systems; Animals; Endocytosis; Endosomal Sorting Complexes Required for Transport; Fungal Proteins/metabolism; Ligases/metabolism; Membrane Transport Proteins/genetics; Membrane Transport Proteins/metabolism; Molecular Sequence Data; Nitrogen/metabolism; Quaternary Ammonium Compounds/pharmacology; Rabbits; Saccharomyces cerevisiae/drug effects; Saccharomyces cerevisiae/metabolism; Saccharomyces cerevisiae Proteins; Ubiquitin-Protein Ligase Complexes; Ubiquitin-Protein Ligases; Ubiquitins/metabolism; Vacuoles
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