title: Constitutive and hyperresponsive signaling by mutant forms of Saccharomyces cerevisiae amino acid sensor Ssy1.
abstract: Sensing of extracellular amino acids results in transcriptional induction of amino acid permease genes in yeast. Ssy1, a membrane protein resembling amino acid permeases, is required for signaling but is apparently unable to transport amino acids and is thus believed to be a sensor. By using a novel genetic screen in which potassium uptake was made dependent on amino acid signaling, we obtained gain-of-function mutations in SSY1. Some alleles confer inducer-independent signaling; others increase the apparent affinity for inducers. The results reveal that amino acid transport is not required for signaling and support the notion that sensing by Ssy1 occurs via its direct interaction with extracellular amino acids.
authors.affiliation: Department of Physiology, Carlsberg Laboratory, DK-2500 Copenhagen Valby, Denmark.
authors.forename: Richard F
authors.initials: RF
authors.lastname: Gaber
authors.forename: Kim
authors.initials: K
authors.lastname: Ottow
authors.forename: Helge A
authors.initials: HA
authors.lastname: Andersen
authors.forename: Morten C
authors.initials: MC
authors.lastname: Kielland-Brandt
mesh_terms: D026905:Amino Acid Transport Systems / Q000235:genetics; D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics; D000596:Amino Acids / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology; D027682:Cation Transport Proteins / Q000235:genetics; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002956:Citrulline / Q000494:pharmacology; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D047908:Intracellular Signaling Peptides and Proteins; D007763:Lac Operon / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010641:Phenotype; D010940:Plant Proteins; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying; D011189:Potassium Chloride / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D014170:Transformation, Genetic; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: C420623:AGP1 protein, S cerevisiae; D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C106976:PTR3 protein, S cerevisiae; D010940:Plant Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C120527:SSY1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C085258:TRK2 protein, S cerevisiae; C068664:TRK1 protein, S cerevisiae; D002956:Citrulline; D011189:Potassium Chloride; D001616:beta-Galactosidase