PMID:10214935
| Citation |
Trchounian, A and Kobayashi, H (1999) Kup is the major K+ uptake system in Escherichia coli upon hyper-osmotic stress at a low pH. FEBS Lett. 447:144-8 |
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| 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. |
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| Keywords |
Adenosine Triphosphatases/genetics; Adenosine Triphosphatases/metabolism; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Carbonyl Cyanide m-Chlorophenyl Hydrazone/pharmacology; Carrier Proteins/genetics; Carrier Proteins/metabolism; Cation Transport Proteins; Dicyclohexylcarbodiimide/pharmacology; Enzyme Inhibitors/pharmacology; Escherichia coli/drug effects; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins; Genes, Bacterial; Hydrogen-Ion Concentration; Ion Transport/drug effects; Ion Transport/genetics; Ionophores/pharmacology; Kinetics; Membrane Proteins/genetics; Membrane Proteins/metabolism; Mutation; Osmotic Pressure; Potassium/metabolism; Proton-Translocating ATPases/antagonists & inhibitors; Receptor, trkA |
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