title: Kup is the major K+ uptake system in Escherichia coli upon hyper-osmotic stress at a low pH.
abstract: The K+ uptake was observed in washed cells of Escherichia coli, wild-type, upon hyper-osmotic stress at pH 5.5 when glucose was supplemented. This uptake had apparent a Km of 0.58 mM and Vmax of 0.10 micromol K+/min/mg protein. Such a K+ uptake was investigated using a mutant defective in Kdp and TrkA but with a functional Kup and a mutant defective in Kdp and Kup but having an active TrkA. The K+ uptake to reach the steady state level as well as the initial K+ influx rate in the first mutant were at least 3.5-fold greater than these values with the second mutant and similar to those of the wild-type. Such differences in the K+ uptake activity were correlated with K+ requirements for growth of these mutants. Moreover, the K+ uptake in the wild-type was blocked by a protonophore (carbonyl cyanide m-chlorophenylhydrazone). Valinomycin, arsenate and N,N'-dicyclohexylcarbodiimide were not effective in changing the K+ uptake. It is suggested that Kup is the major K+ uptake system in E. coli upon hyper-osmotic stress at a low pH.
authors.affiliation: Faculty of Pharmaceutical Sciences, Chiba University, Japan. kensafiz@ysu.am
authors.forename: A
authors.initials: A
authors.lastname: Trchounian
authors.forename: H
authors.initials: H
authors.lastname: Kobayashi
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D027682:Cation Transport Proteins; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport / Q000187:drug effects / Q000235:genetics; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009997:Osmotic Pressure; D011188:Potassium / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D020917:Receptor, trkA
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D007476:Ionophores; D008565:Membrane Proteins; D004024:Dicyclohexylcarbodiimide; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D020917:Receptor, trkA; D000251:Adenosine Triphosphatases; C058166:potassium translocating Kdp-ATPase, E coli; D006180:Proton-Translocating ATPases; D011188:Potassium