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J. Bacteriol., Feb 1997, 1007-1012, Vol 179, No. 4
GP Ferguson, Y Nikolaev, D McLaggan, M Maclean and IR Booth
The role of the KefB and KefC potassium efflux systems in protecting
Escherichia coli cells against the toxic effects of the electrophile N-
ethylmaleimide has been investigated. Activation of KefB and KefC aids the
survival of cells exposed to high concentrations (> 100 microM) of NEM.
High potassium concentrations reduce the protection afforded by activation
of KefB and KefC, but the possession of these systems is still important
under these conditions. The Kdp system, which confers sensitivity to the
electrophile methylglyoxal, did not affect the survival of cells exposed to
NEM. Survival is correlated with the reduction of the cytoplasmic pH upon
activation of the channels. In particular, the kinetics of the
intracellular pH (pHi) change are crucial to the retention of viability of
cells exposed to NEM; slow acidification does not protect cells as
effectively as rapid lowering of pHi. Cells treated with low levels of NEM
(10 microM) recover faster if they activate KefB and KefC, and this
correlates with changes in pHi. The pHi does not significantly alter the
rate of NEM metabolism. The possible mechanisms by which protection against
the electrophile is mediated are discussed.
Copyright © 1997, American Society for Microbiology
Survival during exposure to the electrophilic reagent N-ethylmaleimide in Escherichia coli: role of KefB and KefC potassium channels
Department of Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, United Kingdom.
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