ACTIVATION OF POTASSIUM CHANNELS DURING METABOLITE DETOXIFICATION IN ESCHERICHIA-COLI

In bacteria the detoxification of compounds as diverse as methylglyoxa l and chlorodinitrobenzene proceeds through the formation of a glutath ione adduct. In the Gram-negative bacteria, e.g. Escherichia coli, suc h glutathione adducts activate one, or both, of a pair of potassium ef flux systems KefB and KefC. These systems share many of the properties of cation-translocating channels in eukaryotes. The activity of these systems has been found to be present in a range of Gram-negative bact eria, but not in the glutathione-deficient species of Gram-positive or ganisms. The conservation of the activity of these systems in a divers e range of organisms suggested a physiological role for these systems. Here we demonstrate that in E. coli cells activation of the KefB effl ux system is essential for the survival of exposure to methylglyoxal. Methylglyoxal can be added to the growth medium or its synthesis can b e stimulated in the cytoplasm. Under both sets of conditions survival is aided by the activity of KefB. Inhibition of KefB activity by the a ddition of 10 mM potassium to the growth medium stimulates methylglyox al-induced cell death. This establishes an essential physiological fun ction for the Kef B system.