Downregulation of the broad-specificity amino acid permease Agp1 mediated by the ubiquitin ligase Rsp5 and the arrestin-like protein Bul1 in yeast

ABSTRACT Most of plasma membrane transporters are downregulated by ubiquitination-dependent endocytosis to avoid the excess uptake their substrates. In Saccharomyces cerevisiae, ubiquitination is mediated HECT-type ubiquitin ligase Rsp5. We report here a mechanism underlying substrate-induced broad-specificity amino acid permease Agp1. First, we found that Agp1 underwent and in response addition asparagine, which substrate Moreover, internalization was dependent on activity Since Rsp5 requires α-arrestin family proteins as adaptors bind with substrates, next developed method genetic screening identify adaptor for endocytosis. This biochemical analysis revealed Bul1, but not its paralogue Bul2, essential Our results support Bul1.