Characterization of the genes encoding a cytochrome oxidase from Thiobacillus ferroxidans ATCC33020 strain

Despite the importance of Thiobacillus ferroxidans in bioremediation and bioleaching, we have only a rudimentary knowledge on its energetic metabolism. To characterize the T. ferroxidans respiratory chains we are studying the genes encoding electron transfer proteins. In this paper, we report the sequence of the cox genes encoding the four subnits of a cytochrome oxidase. Theses genes are located immediately upstream from the rus gene encoding rusticyanin and downstream from the cyc2, cyc1 genes and ORF1, encoding respectively a higher molecular weight cytochrome c , a c 4 -type cytochrome ( c 552 ) and a putative periplasmic protein of unknown function. Analysis of the polypeptides encoded by the four cox gene reveals different interesting points: (i) the higher homology with the sub-units I and II of T. ferrooxidans cytochrome oxidase is found with Synechocystis sp., Anabaena sp. Synechococcus vulcanus enzyme, which is a likely candidte for the primordial oxidase; (ii) according to the topology of sub-unit I, the active site, where oxygen binds and is reduced to water, is located as in the other known cytochrome oxidases; (iii) nearly all the residues involved in the proton pathways are present in sub-unit I suggesting that this cytochrome is able to generate a proton motive force; (iv) this is a cytochrome and not a quinol oxidase since the residues involved in the copper binding site and in cytochrome c interaction are conserved (v) the molecular weight deduced from the sequence of cox1 does not fit the molecular weight of the T. ferrooxidans aa 3 cytochrome oxidases sub-unit I characterized, suggesting the presence of two different cytochrome oxidases.