title: The Na+ and K+ transport deficiency of an E. coli mutant lacking the NhaA and NhaB proteins is apparent and caused by impaired osmoregulation.
abstract: Cells of the E. coli mutant EP432, which lacks the two Na+/H+ antiporters, NhaA and NhaB, have been reported to have an impaired sodium transport activity (Harel-Bronstein et al. (1995) J. Biol. Chem. 270, 3816-3822). Here we report that active transport of Na+ in EP432 cells can be restored to wild-type levels, either by a high K+ concentration or by an increase in the medium osmolarity. We suggest that this mutant is primarily deficient in osmoregulation rather than in cation transport per se.
authors.affiliation: Department of Medical Chemistry, Institute of Biomedical Sciences, University of Helsinki, Finland. marina.verkhovskaya@helsinki.fi
authors.forename: M L
authors.initials: ML
authors.lastname: Verkhovskaya
authors.forename: B
authors.initials: B
authors.lastname: Barquera
authors.forename: M I
authors.initials: MI
authors.lastname: Verkhovsky
authors.forename: M
authors.initials: M
authors.lastname: Wikström
mesh_terms: D001426:Bacterial Proteins; D002455:Cell Division; D003593:Cytoplasm / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D017136:Ion Transport; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D014882:Water-Electrolyte Balance
chemical_list: 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; D011188:Potassium