RAPISARDA Viviana Andrea
congresos y reuniones científicas
Toxicity for hydropeoxide in Escherichia coli with differential expression of the NADH dehydrogenase-2
VOLENTINI, S. I.; FARÍAS, R. N.; RAPISARDA, V. A.; RODRÍGUEZ-MONTELONGO, L.
Congreso; X PABMB Congress, XLI Reunión anual de SAIB y XX Reunión anual SAN; 2005
The respiratory chain of Escherichia coli (E. coli) contains two NADH dehydrogenases. In the presence of its substrate, NDH-1 is able to generate a proton gradient whereas NDH-2 does not, partially uncoupling the respiratory chain. Our group demonstrated that: a) NDH-2 is a Cu(II) reductase; b) mutants in NDH-2 grow with more difficulty that the wild type strains, in media with high copper concentration and deficient in this metal; c) NDH-2 is damaged when membranes of E. coli were incubated in presence of copper and peroxides. To further investigate the participation of NDH-2 in the oxidative stress, we measured the oxygen consumption, after incubation with an organic peroxide (t-BOOH), by cells that over-express or lack the NDH-2. The results show that both mutants were more sensitive to peroxides damage than the wild-type strains. The damage was magnified in NDH-1 deficient strain. Therefore in controlled conditions, the presence of NDH-2 is positive for the cell because the enzyme would act as scavenger of free radicals avoiding damage on other components of the respiratory chain. In strains with excessive activity the scavenger capacity could be overcome by the oxidative capacity.