The N-terminal domain of the yeast permease Bap2p plays a role in its degradation.
The amino acid permease Bap2p in Saccharomyces cerevisiae mediates a major part of the uptake of leucine, isoleucine, and valine from media containing a preferred nitrogen source. Although the transcriptional controls of BAP2 have been well studied, the posttranslational down-regulation mechanisms for Bap2p have not been established. Here we show that Bap2p is subject to a starvation-induced degradation upon rapamycin treatment or cultivation with proline as the sole nitrogen source. The starvation-induced degradation of Bap2p was dependent on the cellular functions of ubiquitination and endocytosis. Down-regulation of the permease required the most probable ubiquitination sites, the lysine residues situated in the N-terminal 49 residues, as well as the C-terminal domain. Furthermore, when the N-terminal domain of Bap2p was fused to the general amino acid permease Gap1p, the resultant chimeric permease became susceptible to the starvation-induced degradation, indicating that the Bap2p N-terminus contains a determinant responsive to the starvation signals.
Omura
F
F
Institute for Fundamental Research, Suntory Ltd., 1-1-1, Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka, 618-8503, Japan. omura@nisiq.net
Kodama
Y
Y
Ashikari
T
T
D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems / Q000235:genetics / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism; D001483:Base Sequence; D004705:Endocytosis; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D025801:Ubiquitin / Q000378:metabolism
D026905:Amino Acid Transport Systems; D000596:Amino Acids; C097094:BAP2 protein, S cerevisiae; D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin