title: SSU1 mediates sulphite efflux in Saccharomyces cerevisiae.
abstract: Ssu1p, a plasma membrane protein involved in sulphite metabolism in Saccharomyces cerevisiae, was found to be required for efficient sulphite efflux. An SSU1 null mutant accumulated significantly more sulphite than wild-type, whereas cells expressing multicopy SSU1 accumulated significantly less. Cells expressing FZF1-4, a dominant allele of a transcriptional activator of SSU1 that confers sulphite resistance, also accumulated less sulphite. beta-galactosidase activity in the FZF1-4 strain carrying an SSU1::lacZ fusion was found to be 8.5-fold higher than in a strain carrying wild-type FZF1, confirming that the heightened resistance was correlated with hyperactivation of SSU1. Multicopy SSU1 was also found to increase the sulphite resistance of a number of unrelated sulphite-sensitive strains by a factor of 3- to 8-fold. Rates of efflux of free sulphite from cells expressing multicopy SSU1 or FZF1-4 were significantly greater than that from wild-type or from a SSU1 null mutant. Rates of efflux of bound sulphite from wild-type, a SSU1 null mutant, a FZF1-4 mutant, or cells expressing multicopy SSU1 were not significantly different, suggesting that Ssu1p specifically mediates efflux of the free form of sulphite.
authors.affiliation: Department of Food Science and Technology, Oregon State University, OR 97331-6602, Corvallis, USA.
authors.forename: H
authors.initials: H
authors.lastname: Park
authors.forename: A T
authors.initials: AT
authors.lastname: Bakalinsky
mesh_terms: D027321:Anion Transport Proteins; D001692:Biological Transport; D004352:Drug Resistance, Microbial; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013447:Sulfites / Q000378:metabolism* / Q000494:pharmacology; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D027321:Anion Transport Proteins; C090870:FZF1 protein, S cerevisiae; D005656:Fungal Proteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; C108311:Ssu1 protein, S cerevisiae; D013447:Sulfites; D015534:Trans-Activators; D014157:Transcription Factors; D050862:Oxidoreductases Acting on Sulfur Group Donors; D001616:beta-Galactosidase