title: Identification of a pH regulated Na(+)/H(+) antiporter of Methanococcus jannaschii.
abstract: The genome of the hyperthermophilic archaeon Methanococcus jannaschii contains three Na(+)/H(+) antiporter related genes Mj0057, Mj1521 and Mj1275. Comparative sequence alignments revealed that Mj0057 and Mj1521 belong to the NhaP family whereas Mj1275 is a member of the NapA family. The genes were cloned and expressed in the double mutant Escherichia coli strain Frag144 (DeltanhaA, DeltanhaB) to analyze their capability of mediating DeltapH driven Na(+) flux in everted vesicles. From the tested clones only Mj0057 displayed Na(+) (Li(+))/H(+) antiporter activity. The transport was pH dependent and occurred at pH 7.0 and below. At pH 6.0 the apparent K(m) values for Na(+) and Li(+) were approximately 10 and 2.5 mM, respectively.
authors.affiliation: Universität Hannover, Institut für Biophysik, Herrenhäuserstr. 2, D-30419, Hannover, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Hellmer
authors.forename: Ralf
authors.initials: R
authors.lastname: Pätzold
authors.forename: Carsten
authors.initials: C
authors.lastname: Zeilinger
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins; D001692:Biological Transport; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000235:genetics; D017017:Methanococcus / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism*
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C102839:NhaA protein, E coli; C491047:NhaB protein, E coli; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium