SURVIVAL DURING EXPOSURE TO THE ELECTROPHILIC REAGENT N-ETHYLMALEIMIDE IN ESCHERICHIA-COLI - ROLE OF KEFB AND KEFC POTASSIUM CHANNELS

The role of the KefB and KefC potassium efflux systems in protecting E scherichia 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 mu M) of NEM. High potassium concentrations reduce the protection afforded by a ctivation of KefB and KefC, but the possession of these systems is sti ll important under these conditions, The Kdp system, which confers sen sitivity to the electrophile methylglyoxal, did not affect the surviva l of cells exposed to NEM. Survival is correlated with the reduction o f the cytoplasmic pH upon activation of the channels, In particular, t he kinetics of the intracellular pH (pH(i)) change are crucial to the retention of viability of cells exposed to NEM; slow acidification doe s not protect tells as effectively as rapid lowering of pH,, Cells tre ated with low levels of NEM (10 mu M) recover faster if they activate KefB and KefC, and this correlates with changes in pH(i), The pH(i) do es not significantly alter the rate of NEM metabolism, The possible me chanisms by which protection against the electrophile is mediated are discussed.