Identification of five Rhodobacter capsulatus genes encoding the equivalent of ND subunits of the mitochondrial NADH-ubiquinone oxidoreductase.

We previously reported the sequencing of two genes (ndhA and ndhI) encoding two of the subunits of the type-I NADH-ubiquinone oxidoreductase from Rhodobacter capsulatus (Rc). The present paper deals with the cloning and characterization of a chromosomal fragment clustering five new Rc genes which encode subunits of this enzyme. This gene cluster is located immediately downstream from ndhA and ndhI, and also contains two unidentified open reading frames (urf2, urf3). The five genes, nuoJ, nuoK, nuoL, nuoM and nuoN, encode proteins related, respectively, to mitochondrial (mt) subunits ND6, ND4L, ND5, ND4 and ND2. The overall organization of the nuo genes identified in Rc shows similarity to that of the Paracoccus denitrificans (Pd) nqo gene cluster.