The ccoNOQP gene cluster codes for a cb-type cytochrome oxidase that functions in aerobic respiration of Rhodobacter capsulatus
1994
Thony-Meyer, L. | Beck, C. | Preisig, O. | Hennecke, H.
The genes for a new type of a haem-copper cytochrome oxidase were cloned from Rhodobacter capsulatus strain 37b4 using the Bradyrhizobium japonicum fixNOQP gene region as a hybridizing probe. Four genes probably organized in an operon (ccoNOQp), were identified; their products share extensive amino acid sequence similarity with the FixN, O, Q and P proteins that have recently been shown to be the subunits of a cb-type oxidase. CcoN is a b-type cytochrome CcoO and CcoP are membrane-bound mono- and dihaem c-type cytochromes and ccoQ is a small membrane protein of unknown function. Genes for a similar oxidase are also present in other non-rhizobial bacterial species such as Azotobacter vinelandii, Agrobacterium tumefaciens and Pseudomonas aeruginosa, as revealed by polymerase chain reaction analysis. A ccoN mutant was constructed whose phenotype in combination with the structural information on the gene products provides evidence that the CcoNOQP oxidase is a cytochrome c oxidase of the cb type which supports aerobic respiration in R. capsulatus and which is probably identical to the cbb3-type oxidase that was recently purified from a different strain of the same species. Mutant analysis also showed that this oxidase has no influence on photosynthetic growth and nitrogen-fixation activity.
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