Reactive Oxygen Species Production by Escherichia coli Respiratory Complex I.

Respiratory complex I couples the electron transfer exclusively from NADH to a quinone with the translocation of protons across the membrane. However, Escherichia coli adapts to imposed high cellular NADPH concentrations by selecting the mutations E183A(F) and E183G(F) that lead to a high catalytic efficiency of complex I with NADPH. Other mutations at position E183(F) resulting in an efficient NADPH oxidation were not selected. Here we show that the naturally occurring variants exhibit a remarkably low level of production of reactive oxygen species, a byproduct of NAD(P)H oxidation, that besides high catalytic efficiency might be favored by natural selection.