POTASSIUM CHANNEL ACTIVATION BY GLUTATHIONE-S-CONJUGATES IN ESCHERICHIA-COLI - PROTECTION AGAINST METHYLGLYOXAL IS MEDIATED BY CYTOPLASMIC ACIDIFICATION

Escherichia coli possesses two glutathione-gated potassium channels, K efB and KefC, that are activated by glutathione-S-conjugates formed wi th methylglyoxal. We demonstrate that activation of the channels leads to cytoplasmic acidification and that this protects cells during elec trophilic attack. Further, we demonstrate that mutants lacking the cha nnels can be protected against the lethal effects of methylglyoxal by acidification of the cytoplasm with a weak acid. The degree of protect ion is determined by the absolute value of the pH(i) and the time at w hich acidification takes place. Alterations in the pH(i) do not accele rate the rate of detoxification of methylglyoxal. The mechanism by whi ch methylglyoxal causes cell death and the implications for pH(i)-medi ated resistance to methylglyoxal are discussed.