Disease relevance of blr2715

• Genes for a microaerobically induced oxidase complex in Bradyrhizobium japonicum are essential for a nitrogen-fixing endosymbiosis [1].
• The ccoNOQP gene cluster codes for a cb-type cytochrome oxidase that functions in aerobic respiration of Rhodobacter capsulatus [2].
• 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 [2].
• The deduced amino acid sequences of four open reading frames identified upstream of the fixGHI region in Azorhizobium caulinodans are very similar to the putative terminal oxidase complex coded by the fixNOQP operons from Rhizobium meliloti and Bradyrhizobium japonicum [3].
• This new oxidase exhibits greater homology to the Escherichia coli cytochrome o subunit I than any of the previously reported B. japonicum terminal oxidase genes [4].

High impact information on blr2715

• The tlpA mutant had a pleiotropic phenotype in that it was defective in the development of a nitrogen fixing endosymbiosis and exhibited a strongly decreased oxidase activity, as compared with the wild-type [5].
• Holocytochrome aa3 was spectroscopically undetectable in the mutant, whereas the apoprotein of subunit one (CoxA) of this oxidase was still synthesized and incorporated into the cytoplasmic membrane [5].
• Furthermore, fixN insertion and fixNO deletion mutants grown microaerobically or anaerobically (with nitrate) exhibited a strong decrease in whole-cell oxidase activity as compared with the wild type [1].
• To analyze the contribution of these 12 invariant histidines of FixN in cofactor binding and function of the Bradyrhizobium japonicum cbb3-type oxidase, they were substituted by valine or alanine by site-directed mutagenesis [6].
• All mutants, except the fixQ mutant, showed clearly altered absorption difference spectra of their membranes and decreased oxidase activities, and they were unable to fix nitrogen symbiotically [7].

Chemical compound and disease context of blr2715

• In contrast to previous results on Bradyrhizobium japonicum, R. tropici showed no significant O2-mediated reduction in the level of either coxA transcription or cytochrome aa3 activity (as measured by ascorbate-N,N,N',N'-tetramethyl-p-phenylenediamine [TMPD] oxidase) even in the cells incubated at 12.5 microM O2 [8].
• Histidine 131, not histidine 43, of the Bradyrhizobium japonicum FixN protein is exposed towards the periplasm and essential for the function of the cbb3-type cytochrome oxidase [9].
• Genetic evidence for 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) as a negative effector of cytochrome terminal oxidase cbb3 production in Rhizobium etli [10].
• A Rhizobium etli Tn5mob-induced mutant (CFN035) exhibits an enhanced capacity to oxidize N,N,N',N', tetramethyl-p -phenylenediamine (TMPD), a presumptive indicator of elevated cytochrome c terminal oxidase activity [10].

Biological context of blr2715

• The Bradyrhizobium japonicum cbb3-type cytochrome oxidase, which supports microaerobic respiration, is a multisubunit enzyme encoded by the genes of the fixNOQP operon [7].
• The possible oxidase biogenesis pathway involves the formation of a primary core complex consisting of FixN and FixO, which allows the subsequent association with FixP to form the complete enzyme [7].
• This 20K cytochrome c appeared to catalyse electron transport from the cytochrome bc1 complex to the aa3-type terminal oxidase and, unlike mitochondrial cytochrome c, was membrane-bound in B. japonicum [11].
• Mutant analysis also showed that this oxidase has no influence on photosynthetic growth and nitrogen-fixation activity [2].
• In this paper, we describe the cloning and sequencing of the coxX gene encoding the large catalytic subunit for a fourth terminal oxidase from B. japonicum [4].

Associations of blr2715 with chemical compounds

• It has been a long-standing hypothesis that the endosymbiotic rhizobia (bacteroids) cope with a concentration of 10 to 20 nM free O2 in legume root nodules by the use of a specialized respiratory electron transport chain terminating with an oxidase that ought to have a high affinity for O2 [12].
• The purified oxidase has TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine) oxidase activity as well as cytochrome c oxidase activity [12].
• The oxidase complex was not able to oxidize a ubiquinol homolog possessing a single isoprenoid unit side chain [13].
• Enzymological studies confirmed presence of Thiosulphate oxidase, sulphite oxidase and Rhodanese, all of which play role in sulfur metabolism pathway [14].

Other interactions of blr2715

• A B. japonicum cycM insertion mutant (COX122) exhibited an oxidase-negative phenotype and apparently lacked cytochrome aa3 in addition to the CycM protein [15].
• However, the S. meliloti ccdA mutant also lacked cytochrome oxidase aa(3), a defect that does not appear to have been reported for other bacteria [16].
• A role for the flavoprotein as a terminal oxidase was implicated based on its high redox potential and its sensitivity to cyanide [17].

Analytical, diagnostic and therapeutic context of blr2715

• Western blot analyses showed that an intact heme binding site in the FixO polypeptide is a prerequisite not only for the synthesis of holo-FixO protein but also for the formation of the entire cbb3-type oxidase complex [18].
• Terminal oxidase cyanide inhibition titration pattern comparisons of the wild type with a coxWXYZ insertion mutant indicated the new oxidase is expressed microaerobically [19].

References