title: Tungsten transport protein A (WtpA) in Pyrococcus furiosus: the first member of a new class of tungstate and molybdate transporters.
abstract: A novel tungstate and molybdate binding protein has been discovered from the hyperthermophilic archaeon Pyrococcus furiosus. This tungstate transport protein A (WtpA) is part of a new ABC transporter system selective for tungstate and molybdate. WtpA has very low sequence similarity with the earlier-characterized transport proteins ModA for molybdate and TupA for tungstate. Its structural gene is present in the genome of numerous archaea and some bacteria. The identification of this new tungstate and molybdate binding protein clarifies the mechanism of tungstate and molybdate transport in organisms that lack the known uptake systems associated with the ModA and TupA proteins, like many archaea. The periplasmic protein of this ABC transporter, WtpA (PF0080), was cloned and expressed in Escherichia coli. Using isothermal titration calorimetry, WtpA was observed to bind tungstate (dissociation constant [K(D)] of 17 +/- 7 pM) and molybdate (K(D) of 11 +/- 5 nM) with a stoichiometry of 1.0 mol oxoanion per mole of protein. These low K(D) values indicate that WtpA has a higher affinity for tungstate than do ModA and TupA and an affinity for molybdate similar to that of ModA. A displacement titration of molybdate-saturated WtpA with tungstate showed that the tungstate effectively replaced the molybdate in the binding site of the protein.
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
authors.forename: Loes E
authors.initials: LE
authors.lastname: Bevers
authors.forename: Peter-Leon
authors.initials: PL
authors.lastname: Hagedoorn
authors.forename: Gerard C
authors.initials: GC
authors.lastname: Krijger
authors.forename: Wilfred R
authors.initials: WR
authors.lastname: Hagen
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D008982:Molybdenum / Q000378:metabolism*; D033902:Periplasmic Binding Proteins / Q000235:genetics; D033903:Periplasmic Proteins / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011485:Protein Binding; D020027:Pyrococcus furiosus / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D017973:Tungsten Compounds / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D019843:Archaeal Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; C098002:ModA protein, E coli; D033902:Periplasmic Binding Proteins; D033903:Periplasmic Proteins; D017973:Tungsten Compounds; C431931:TupA protein, Eubacterium acidaminophilum; C044659:molybdate; D008982:Molybdenum; C045951:tungstate