Protection of the DNA during the exposure of Escherichia coli cells to a toxic metabolite: the role of the KefB and KefC potassium channels

The effect of the toxic metabolite methylglyoxal on the DNA of Escherichia coil cells has been investigated. Exposure of E. coli cells to methylglyoxa l reduces the transformability of plasmid DNA and results in the degradatio n of genomic DNA. The activity of the KefB and KefC potassium channels prot ects E. coil cells against methylglyoxal and limits the amount of DNA damag e. In mutants lacking KefB and KefC, methylglyoxal-induced DNA damage was r educed by incubation with a weak acid that lowers the pi-ii to the same ext ent as through KefB and KefC activation. This provides evidence that acidif ication of the cytoplasm protects E. coil DNA against methylglyoxal. By the analysis of cells lacking UvrA, we demonstrate that this repair protein is required for the degradation of the DNA upon methylglyoxal exposure. Howev er, protection by KefB and KefC occurred independently of UvrA. Although we present evidence that exposure of E. coli cells to methylglyoxal results i n DNA degradation, our results suggest this event is not essential for meth ylglyoxal-induced death. The implications of these findings will be discuss ed.