Inactivation of the Na+-translocating NADH:ubiquinone oxidoreductase from Vibrio alginolyticus by reactive oxygen species

Abstract

The Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) from Vibrio alginolyticus was inactivated by reactive oxygen species. Highest Na+-NQR activity was observed in anaerobically prepared membranes that exhibited 1:1 coupling of NADH oxidation and Q reduction activities (1.6 U mg 1). Optical and EPR spectroscopy documented the presence of b-type cytochromes, a [2Fe 2S] cluster and an organic radical signal in anaerobically prepared membranes from V. alginolyticus. It is shown that the [2Fe 2S] cluster previously assigned to the Na+-NQR originates from the succinate dehydrogenase or the related enzyme fumarate reductase.