IDENTIFICATION OF THE MAJOR OXIDATIVELY DAMAGED PROTEINS IN ESCHERICHIA-COLI-CELLS EXPOSED TO OXIDATIVE STRESS

In the present study we have analyzed protein oxidation on Escherichia coli when these cells were submitted to different stress conditions s uch as hydrogen peroxide, superoxide-generating compounds, and iron ov erloading, Carbonyl groups on oxidized cell proteins were examined by Western blot immunoassay. When anaerobically grown E, coil cells were exposed to hydrogen peroxide stress, alcohol dehydrogenase E, elongati on factor G, the heat shock protein DNA K, oligopeptide-binding protei n A, enolase, and the outer membrane protein A were identified as the major protein targets, A similar immunostained band pattern was found when cells were shifted from anaerobic to aerobic conditions in the pr esence of different concentrations of iron; it is relevant to note tha t oxidation of outer membrane protein C, not observed in peroxide stre ss conditions, was clearly detected as the concentration of iron was i ncreased in the culture media, The hydrogen peroxide stress performed under aerobic conditions affected the beta-subunit of F0F1-ATPase; the rest of the oxidized protein pattern was very similar to that found f or anaerobic conditions, with the exception of alcohol dehydrogenase E , a protein not synthesized aerobically, Cells submitted to superoxide stress using menadione showed a more specific pattern in which elonga tion factor G and the beta-subunit of F0F1-ATPase were affected signif icantly, When paraquat was used, although the degree of oxidative dama ge was lower, the same two modified proteins were detected, and DNA K was also clearly damaged, Cell. viability was affected to different ex tents depending on the type of stress exerted, The results described i n this paper provide data about the in vivo effects of oxidative stres s on protein oxidation and give insights into understanding how such m odifications can affect cellular functions.