Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous work from this laboratory revealed that alterations in the structure of the ccoNOQP operon of Rhodobacter sphaeroides 2.4.1 could lead to induction of the photosynthetic apparatus under aerobic growth conditions. Immediately downstream of the ccoNOQP operon is the rdxB gene, the first gene of the rdxBHIS cluster. The rdxB gene product is predicted to encode a membrane protein which can bind two [4Fe-4S] clusters. The ccoP gene product is a diheme cytochrome which is a component of the cbb3-type cytochrome oxidase. Under aerobic growth conditions, strains possessing ccoP and rdxB mutations both singly and in combination produced light-harvesting complexes, suggesting that normal functioning of these proteins is required to maintain repression of photosynthesis gene expression in the presence of oxygen. Analysis of the expression of puc::lacZ fusions under aerobic conditions revealed an approximately 12-fold increase in puc operon expression in the RDXB1 and CCOP1 mutant strains compared with that for wild-type 2.4.1. Similarly, puf::lacZ activity was observed to be elevated fourfold above wild-type levels. Further indication of the importance of the RdxB and CcoP proteins was derived from studies of mutant and wild-type cells grown under anoxygenic photosynthetic and nitrogen-fixing conditions. These mutant strains were observed to accumulate spheroidenone to approximately 50% or more of the total carotenoid. In wild-type cultures, spheroidenone normally accumulates to approximately 10 to 20% of the total carotenoid under the same growth conditions. This effect was most pronounced when both the rdxB and the ccoP mutations were present together in cells cultured under nitrogen-fixing photosynthetic growth conditions in which spheroidenone represented approximately 90% of the total carotenoid. We propose that mutations in the rdxB or ccoP gene may lead to changes in a membrane-generated redox signal or the accumulation of a critical redox intermediate in the mutant strains which results in increased photosynthesis gene expression under aerobic conditions by alteration of the activity of a transcriptional regulator(s) of photosynthesis gene expression. Mutations in these genes also appear to posttranscriptionally influence the terminal step of carotenoid biogenesis. Potential regulators interacting with an aberrant redox signal in the mutants and the possible nature of such a redox signal are discussed.
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PMID:Evidence for the role of redox carriers in photosynthesis gene expression and carotenoid biosynthesis in Rhodobacter sphaeroides 2.4.1. 906 41

To further understand the proposed signal transduction pathway involving the presumed redox proteins RdxBH and cbb3 cytochrome oxidase in Rhodobacter sphaeroides 2.4.1, a series of mutants lacking components of both the Prr two-component activation system and the cbb3-type cytochrome oxidase or RdxBH were constructed. We report that under highly aerobic conditions, aberrant photosynthesis gene expression and spectral complex formation typical of cbb3- or RdxBH-deficient mutants were no longer observed when either prrA (encoding the response regulator of the Prr system) or prrB (encoding the presumed sensor kinase) was also deleted. These double-mutant strains are phenotypically identical to single-mutant PrrA and PrrB strains, suggesting that the signal(s) originating from the cbb3 terminal oxidase affects downstream puc and puf operon expression by acting exclusively through the Prr system. When the same double-mutant strains were examined under anaerobic dark dimethyl sulfoxide growth conditions, photosynthesis gene expression was obligatorily linked to the two-component activation system. However, photosynthesis gene expression under the same growth conditions was significantly higher in the cbb3 mutant strain when compared to that in the wild type. Similarly, under anaerobic photosynthetic conditions the high levels of the oxidized carotenoid, spheroidenone, which accumulate in cbb3-deficient mutants were nearly restored to normal in a PrrB- CcoP- double mutant. This observation, together with previously published results, suggests that the regulation of the CrtA-catalyzed reaction possesses both transcriptional and posttranscriptional regulatory effectors. We propose that the cbb3 cytochrome oxidase, which by definition can interact with external oxygen, serves to control the activity of the Prr two-component activation system under both aerobic and anaerobic conditions. Although independent from the cbb3 oxidase, the RdxBH proteins are also required for normal functioning of the Prr two-component activation system and are therefore believed to lie between the cbb3 oxidase in this oxygen-sensing, redox signaling pathway and the Prr activation system.
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PMID:A redox-responsive pathway for aerobic regulation of photosynthesis gene expression in Rhodobacter sphaeroides 2.4.1. 969 49

Previously, we reported that rdxB, encoding a likely membrane-bound two [4Fe-4S]-containing center, is involved in the aerobic regulation of photosystem gene expression in Rhodobacter sphaeroides 2.4.1. To further investigate the role of rdxB as well as other genes of the rdxBHIS operon on photosystem gene expression, we constructed a series of nonpolar, in-frame deletion mutations in each of the rdx genes. Using both puc and puf operon lacZ fusions to monitor photosystem gene expression, under aerobic conditions, in each of the mutant strains revealed significant increased photosynthesis gene expression. In the case of mutations in either rdxH, rdxI, or rdxS, the aerobic induction of photosystem gene expression is believed to be indirect by virtue of a posttranscriptional effect on cbb(3) cytochrome oxidase structure and integrity. For RdxB, we suggest that this redox protein has a more direct effect on photosystem gene expression by virtue of its interaction with the cbb(3) oxidase. An associated phenotype, involving the enhanced conversion of the carotenoid spheroidene to spheroidenone, is also observed in the RdxB, -H, -I, and -S mutant strains. This phenotype is also suggested to be the result of the role of the rdxBHIS locus in cbb(3) oxidase activity and/or structure. RdxI is suggested to be a new class of metal transporter of the CPx-type ATPases.
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PMID:Genetic and phenotypic analyses of the rdx locus of Rhodobacter sphaeroides 2.4.1. 1085 80