title: A Rhodobacter capsulatus member of a universal permease family imports molybdate and other oxyanions.
abstract: Molybdenum (Mo) is an important trace element that is toxic at high concentrations. To resolve the mechanisms underlying Mo toxicity, Rhodobacter capsulatus mutants tolerant to high Mo concentrations were isolated by random transposon Tn5 mutagenesis. The insertion sites of six independent isolates mapped within the same gene predicted to code for a permease of unknown function located in the cytoplasmic membrane. During growth under Mo-replete conditions, the wild-type strain accumulated considerably more Mo than the permease mutant. For mutants defective for the permease, the high-affinity molybdate importer ModABC, or both transporters, in vivo Mo-dependent nitrogenase (Mo-nitrogenase) activities at different Mo concentrations suggested that ModABC and the permease import molybdate in nanomolar and micromolar ranges, respectively. Like the permease mutants, a mutant defective for ATP sulfurylase tolerated high Mo concentrations, suggesting that ATP sulfurylase is the main target of Mo inhibition in R. capsulatus. Sulfate-dependent growth of a double mutant defective for the permease and the high-affinity sulfate importer CysTWA was reduced compared to those of the single mutants, implying that the permease plays an important role in sulfate uptake. In addition, permease mutants tolerated higher tungstate and vanadate concentrations than the wild type, suggesting that the permease acts as a general oxyanion importer. We propose to call this permease PerO (for oxyanion permease). It is the first reported bacterial molybdate transporter outside the ABC transporter family.
authors.affiliation: Ruhr-Universität Bochum, Fakultät für Biologie und Biotechnologie, Biologie der Mikroorganismen, Bochum, Germany.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gisin
authors.forename: Alexandra
authors.initials: A
authors.lastname: Müller
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Pfänder
authors.forename: Silke
authors.initials: S
authors.lastname: Leimkühler
authors.forename: Franz
authors.initials: F
authors.lastname: Narberhaus
authors.forename: Bernd
authors.initials: B
authors.lastname: Masepohl
mesh_terms: D000838:Anions; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D008982:Molybdenum / Q000378:metabolism* / Q000633:toxicity*; D016254:Mutagenesis, Insertional; D016354:Rhodobacter capsulatus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013430:Sulfate Adenylyltransferase / Q000037:antagonists & inhibitors* / Q000235:genetics; D017973:Tungsten Compounds / Q000378:metabolism / Q000633:toxicity; D014638:Vanadates / Q000378:metabolism / Q000633:toxicity
chemical_list: D000838:Anions; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D026901:Membrane Transport Proteins; D017973:Tungsten Compounds; C044659:molybdate; D014638:Vanadates; D008982:Molybdenum; D013430:Sulfate Adenylyltransferase; C045951:tungstate