Kup is the major K+ uptake system in Escherichia coli upon hyper‐osmotic stress at a low pH

FEBS Letters

Trchounian, Armen¹  Kobayashi, Hiroshi¹ 

[1] Faculty of Pharmaceutical Sciences, Chiba University, Chiba 263, Japan

关键词: K+ uptake;    Kup;    TrkA;    Low pH;    Escherichia coli;    F0F1;    the H+-translocating ATP synthase;    TrkA(G;    H);    Kup;    the constitutive low affinity K+ uptake systems in E. coli;    Kdp;    the inducible high affinity K+ uptake system in E. coli;    CCCP;    carbonyl cyanide m-chlorophenylhydrazone;    DCCD;    N;    N′-dicyclohexylcarbodiimide;    EDTA;    ethylenediaminotetraacetic acid;    μ̄H+;    transmembrane proton electrochemical gradient;    ΔΨ;    the membrane electric potential;   

DOI  :  10.1016/S0014-5793(99)00288-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 K _m of 0.58 mM and V _max of 0.10 μmol 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.

【 授权许可】

Unknown