CHARACTERISTICS OF THE ENERGY-TRANSDUCING NADH-QUINONE OXIDOREDUCTASEOF PARACOCCUS-DENITRIFICANS AS REVEALED BY BIOCHEMICAL, BIOPHYSICAL, AND MOLECULAR BIOLOGICAL APPROACHES

A comparison of the mitochondrial NADH-ubiquinone oxidoreductase an th e energy-transducing NADH-quinone oxidoreductase (NDH-1) of Paracoccus denitrificans revealed that both systems have similar electron-transf er and energy-transduction pathways. In addition, both complexes are s ensitive to the same inhibitors and contain similar electron carriers, suggesting that the Paracoccus NDH-1 may serve as a useful model syst em for the study of the human enzyme complex. The gene cluster encodin g the Paracoccus NDH-1 has been cloned and sequenced. It is composed o f 18,106 base pairs and contains 14 structural genes and six unidentif ied reading frames (URFs). The structural genes, URFs, and their polyp eptides have been characterized. We also discuss nucleotide sequences which are believed to play a role in the regulation of the NDH-1 gene cluster and Paracoccus NDH-1 subunits which may contain the binding si tes of substrates and/or electron carriers.