tailieunhanh - Báo cáo Y học: Inactivation of the Na+-translocating NADH:ubiquinone oxidoreductase from Vibrio alginolyticus by reactive oxygen species

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 ( UÆmg)1). Optical and EPR spectroscopy documented the presence of b-type cytochromes, a [2Fe)2S] cluster and an organic radical signal in anaerobically pre- pared membranes from V. alginolyticus. | Eur. J. Biochem. 269 1287-1292 2002 FEBS 2002 Inactivation of the Na -translocating NADH ubiquinone oxidoreductase from Vibrio alginolyticus by reactive oxygen species Julia Steuber1 Michele Rufibach1. Gunter Fritz2. Frank Neese3 and Peter Dimroth1 1 Mikrobiologisches Institut der Eidgenossischen Technischen Hochschule ETH-Zentrum Zurich Switzerland 2Biochemisches Institut Universitat Zurich Switzerland 3Mathematisch-naturwissenschaftliche Sektion Fachbereich Biologie UniversitaÈt Konstanz Germany 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 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 pre pared 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. Keywords electrochemical sodium gradient reactive oxygen species Vibrio Na transport NADH quinone oxido-reductase. The marine bacterium Vibrio alginolyticus possesses a Na -translocating NADH Q oxidoreductase Na -NQR that maintains an electrochemical sodium gradient required for nutrient uptake and motility 1-5 . This respiratory sodium pump contains one Fe-S cluster noncovalently bound FAD covalently bound FMN and ubiquinone-8 as redox cofactors 2 6-8 that are likely to participate in NADH oxidation electron transfer Na transport and Q reduction. Sequence analysis of the six subunits of the Na -NQR from V. alginolyticus NqrA-NqrF showed that only the NqrF or b- subunit comprises a cysteine motif Cys69 Cys75 Cys78 and Cys110 required for ligation of one Fe-S cluster 3 4 . Tightly bound ubisemiquinones were proposed to play a central role during the .