Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An azido-ubiquinone derivative, 3-azido-2-methyl-5-methoxy-6-(3,7-dimethyloctyl)-1,4-benzoquinone, was used to study the ubiquinone-protein interaction and to identify the ubiquinone-binding proteins in yeast mitochondrial ubiquinone-cytochrome c reductase. The phospholipids and Q6 in purified reductase were removed by repeated ammonium sulfate precipitation in the presence of 0.5% sodium cholate. The resulting phospholipid- and ubiquinone-depleted reductase shows no enzymatic activity; activity can be completely restored by the addition of phospholipids and Q6 or Q2. The ubiquinone- and phospholipid-replenished ubiquinonol-cytochrome c reductase is also fully active upon reconstituting with bovine succinate-ubiquinone reductase to form succinate-cytochrome c reductase. When an azido-ubiquinone derivative was added to the ubiquinone and phospholipid-depleted reductase in the dark, followed by the addition of phospholipids, partial reconstitutive activity was restored, while full ubiquinol-cytochrome c reductase activity was observed when Q2H2 was used as substrate in the assay mixture. Apparently, the large amount of Q2H2 present in the assay mixture displaces the azido-ubiquinone in the system. Photolysis of the azido-Q-treated reductase with long-wavelength ultraviolet light abolishes about 70% of both the restored reconstitutive activity and Q2H2-cytochrome c reductase activity. The activity loss is directly proportional to the covalent binding of [3H]azido-ubiquinone to the reductase protein. When the photolyzed, [3H]azido-ubiquinone-treated sample was subjected to SDS-polyacrylamide gel electrophoresis followed by analysis of the distribution of radioactivity among the subunits, the cytochrome b protein and a protein with an apparent molecular weight of 14 000 were heavily labeled. The amount of radioactive labeling in both these proteins was affected by the presence of phospholipids.
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PMID:Identification of ubiquinone-binding proteins in yeast mitochondrial ubiquinol-cytochrome c reductase using an azido-ubiquinone derivative. 300 77

The chemical composition, properties and activation mechanism of the O2(-)-forming NADPH oxidase of phagocytes were investigated, using partially purified enzyme preparations. Highly active NADPH oxidase was extracted as an aggregate of high Mr from the membranes of neutrophils and macrophages. The enzyme complex contained phospholipids and cytochrome b-245, very little FAD and almost no quinones or NAD(P)H-dye reductase activity. The purification of a polypeptide with a relative molecular mass of 31 500 strictly paralleled the purification of NADPH oxidase, suggesting that this polypeptide is a component of the enzyme. This protein was identified as cytochrome b -245 after dissociation of the proteolipid complex and purification of the cytochrome moiety. The 31 500 Mr protein was phosphorylated in enzyme preparations from activated but not from resting cells. The results indicate that: cytochrome b-245 is a major component of NADPH oxidase; the involvement of NAD(P)H dye reductases in the O2(-)-forming activity is questionable; the cytochrome b-245: FAD ratio in the enzyme complex is much higher than that indicated in crude preparations; the Mr of pig neutrophil cytochrome b-245 is 31 500; the activation of the O-2-forming system involves a process of phosphorylation of cytochrome b-245.
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PMID:Respiratory response of phagocytes: terminal NADPH oxidase and the mechanisms of its activation. 301 13

Dimeric ubiquinol:cytochrome c reductase of Neurospora mitochondria was isolated as a protein-Triton complex and free of ubiquinol (Q). The enzyme was incorporated into phosphatidylcholine membranes together with Q. The effects of varying the molar ratio of Q to enzyme on the electron transfer from duroquinol (DHQ2) to the cytochromes c, c1 and b were studied. The rate of electron flow from DQH2 to cytochrome c was 15 times increased by Q and was maximal when one molecule of Q was bound to one enzyme dimer. The apparent Km value for DQH2 of the Q-free enzyme was 5 microM and of the Q-supplemented enzyme 25 microM. The pre-steady-state rate of electron transfer from DQH2 to cytochrome c1 was also 15 times increased by Q and was maximal with one Q molecule bound to one enzyme dimer. This effect of Q was inhibited by antimycin. The pre-steady-state rate of electron transfer from DQH2 to cytochrome b was 5 times decreased when Q was bound to the enzyme and this effect of Q was insensitive to myxothiazol. The H+/2e- stoichiometry with DQH2 as substrate of the Q-supplemented enzyme was 3.6. These results are interpreted in accordance with a Q-cycle mechanism operating in a dimeric cytochrome reductase. Each enzyme monomer catalyses a single electron transfer from the QH2-oxidation centre to the Q-reduction centre and the two monomers cooperate in the reduction of Q to QH2 at one Q-reduction centre. This centre contains two different binding sites for Q. DQH2 does not properly react at the QH2-oxidation centre. DQH2, however, binds to the loose Q-binding site of the Q-reduction centre and reduces the Q bound to the tight Q-binding site of the centre. The QH2 thus formed at the Q-reduction centre serves as electron donor for the QH2-oxidation centre.
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PMID:Dimeric ubiquinol:cytochrome c reductase of Neurospora mitochondria contains one cooperative ubiquinone-reduction centre. 301 18

The NADPH oxidase in neutrophils was specifically solubilized from membrane vesicles of porcine blood neutrophils and rapidly concentrated by immunoprecipitation with cross-reacting anti-P-450 reductase IgG. The precipitates from both myristic acid-stimulated and resting cells contained one third of the cytochrome b-558 and were slightly contaminated with myeloperoxidase. The immunoprecipitate from stimulated cells gave rhombic high-spin ESR signals of a heme at g = 6.47 and 5.49, which were insensitive to KCN, whereas the preparation from resting cells did not give these signals. The rhombic high-spin signals are discussed in view of the participation of cytochrome b-558 in the NADPH oxidase system.
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PMID:ESR signals from stimulated and resting porcine blood neutrophils. 303 84

Formate dehydrogenase from Pseudomonas aeruginosa contains molybdenum, a [4Fe-4S] cluster and cytochrome b. This paper reports the detection of molybdenum as Mo(V) by e.p.r. spectroscopy. In order to generate Mo(V) signals, addition of amounts of excess formate varying between 10- and 50-fold over enzyme, followed by 200-fold excess of sodium dithionite, were used. Two Mo(V) species were observed. One, the major component, has g1 = 2.012, g2 = 1.985 and g3 = 1.968, appeared at low concentrations of formate and increased linearly in intensity with increasing concentrations of formate up to 25-fold excess over the enzyme. At higher formate concentration this signal disappeared. The appearance and disappearance of this Mo(V) signal seems to parallel the state of reduction of the [4Fe-4S] clusters. A second, minor, Mo(V) species with g-values g1 = 1.996, g2 = 1.981 and g3 = 1.941 appears at a constant level during the formate-dithionite titration. No evidence has been obtained for nuclear hyperfine coupling to protons. The major Mo(V) species has unusual e.p.r. signals compared with other molybdenum-containing enzymes, except for that observed in the formate dehydrogenase from Methanobacterium formicicum [Barber, Siegel, Schauer, May & Ferry (1983) J. Biol. Chem. 258, 10839-10845]. The present work suggests that the enzyme is acting as a CO2 reductase, with dithionite as an electron donor to a [4Fe-4S] cluster, which in turn donates electrons to molybdenum, producing a Mo(V) species with CO2 bound to the metal.
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PMID:Purification and properties of formate dehydrogenase from Pseudomonas aeruginosa. Electron-paramagnetic-resonance studies on the molybdenum centre. 303 82

Erythrobacter sp. OCh 114, an aerobic photosynthetic bacterium, had trimethylamine N-oxide (TMAO) reductase activity, which increased when the culture medium contained TMAO. The reductase was located in the periplasm. The bacteria grew anaerobically in the presence of TMAO. These results suggested that Erythrobacter OCh 114 has the ability to reduce TMAO through the respiratory chain. The TMAO respiration system of this organism was different from those of facultative purple photosynthetic bacteria in two respects: (a) TMAO reductase did not have activity to reduce dimethyl sulfoxide and (b) soluble c-type cytochrome, cytochrome c551, and cytochrome b-c1 complex appeared to be involved. The photochemical activity, which is usually inoperative in the anaerobic cell suspension, was restored by TMAO, suggesting that the photosynthesis and the TMAO respiration share a common electron transfer chain.
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PMID:Trimethylamine N-oxide respiration by aerobic photosynthetic bacterium, Erythrobacter sp. OCh 114. 317 May 12

Tissue, cellular, and subcellular distributions of OM cytochrome b-mediated NADH-semidehydroascorbate (SDA) reductase activity were investigated in rat. NADH-SDA reductase activity was found in the post-nuclear particulate fractions of liver, kidney, adrenal gland, heart, brain, lung, and spleen of rat. Liver, kidney, and adrenal gland had higher NADH-SDA reductase activity than other tissues, and OM cytochrome b-dependent activity was 60-70% of the total activity. On the other hand, almost all of the reductase activity of heart and brain cells was mediated by OM cytochrome b. The ratio of the OM cytochrome b-mediated activities of NADH-SDA reductase to rotenone-insensitive NADH-cytochrome c reductase varied among these tissues. OM cytochrome b-mediated NADH-SDA reductase and rotenone-insensitive NADH-cytochrome c reductase activities were mainly present in the parenchymal cells of rat liver. The localization of the cytochrome-mediated reductase activities in the outer mitochondrial membrane was confirmed by subfractionation of liver mitochondria. Among the submicrosomal fractions, OM cytochrome b-mediated NADH-SDA reductase activity was highest in the cis-Golgi membrane fraction, in which monoamine oxidase activity was also highest. On the other hand, OM cytochrome b-mediated rotenone-insensitive NADH-cytochrome c reductase activity showed a slightly different distribution pattern from the NADH-SDA reductase activity. Thenoyltrifluoroacetone (TTFA), a metal chelator, effectively inhibited the NADH-SDA reductase activity, though other metal chelators did not affect the activity. TTFA failed to inhibit rotenone-insensitive NADH-cytochrome c reductase activity at the concentration which gave complete inhibition of NADH-SDA reductase activity.
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PMID:Subcellular distribution of OM cytochrome b-mediated NADH-semidehydroascorbate reductase activity in rat liver. 357 Nov 84

A succinate-coenzyme Q reductase (complex II) was isolated in highly purified form from Ascaris muscle mitochondria by detergent solubilization, ammonium sulfate fractionation and gel filtration on a Sephadex G-200 column. The enzyme preparation catalyzes electron transfer from succinate to coenzyme Q1 with a specific activity of 1.2 mumol coenzyme Q1 reduced per min per mg protein at 25 degrees C. The isolated complex II is essentially free of NADH-ferricyanide reductase, reduced CoQ2-cytochrome c reductase and cytochrome c oxidase and consists of four major polypeptides with apparent molecular weights of 66 000, 27 000, 12 000 and 11 000 and two minor ones with Mr of 36 000 and 16 000. The complex II contained cytochrome b-558, a major constituent cytochrome of Ascaris mitochondria, at a concentration of 3.6 nmol per mg protein, but neither other cytochromes nor quinone. The cytochrome b-558 in the complex II was reduced with succinate. In the presence of Ascaris NADH-cytochrome c reductase (complex I-III) (Takamiya, S., Furushima, R. and Oya, H. (1984) Mol. Biochem. Parasitol. 13, 121-134), the cytochrome b-558 in complex II was also reduced with NADH and reoxidized with fumarate. These results suggest the cytochrome b-558 to function as an electron carrier between NADH dehydrogenase and succinate dehydrogenase in the Ascaris NADH-fumarate reductase system.
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PMID:Electron-transfer complexes of Ascaris suum muscle mitochondria. II. Succinate-coenzyme Q reductase (complex II) associated with substrate-reducible cytochrome b-558. 375 51

Three patients (two sisters and a brother) in one family are described with chronic granulomatous disease. The granulocytes of these patients did not respond with a metabolic burst to various stimuli and failed to kill catalase-positive microorganisms. The magnitude of the cytochrome b signal in the optical spectrum of the patients' granulocytes was less than 4% of the normal value, whereas the amount of noncovalently bound flavin in these cells was normal. The mode of inheritance of the genetic defect in this family is autosomal because the granulocytes of both parents (first cousins) and a nonaffected sister of the patients expressed 70-80% of the normal cytochrome b signal, showed low-normal or subnormal oxidative reactions during stimulation, and did not display mosaicism in the stimulated nitroblue-tetrazolium slide test. Somatic cell hybridization was performed between the monocytes from the affected boy in this family with monocytes from either a cytochrome b-negative male patient with X-linked chronic granulomatous disease or a cytochrome b-positive male patient with the classic autosomal form of this disease. In both combinations, monocyte hybrids were observed with nitroblue tetrazolium reductase activity after stimulation with phorbol myristate acetate. This complementation of the oxidase activity required protein synthesis. Our results prove that the defect in this family is genetically distinct from that in the other two forms of chronic granulomatous disease. Moreover, our results also indicate that the expression of cytochrome b in human phagocytes is coded by at least two loci, one on the X chromosome and one on an autosome.
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PMID:Cytochrome b deficiency in an autosomal form of chronic granulomatous disease. A third form of chronic granulomatous disease recognized by monocyte hybridization. 398 Jul 31

1. Escherichia coli 156:53D2 synthesized ubiquinone only when the growth medium was supplemented with 4-hydroxybenzoate acid. 2. Little or no vitamin K(2) was formed by the mutant under the growth conditions employed, in contrast with wild-type strains. 3. In the mutant ubiquinone deficiency was correlated with low respiration and with low particulate NADH-oxidase and NADH-cytochrome b(1)-reductase activity. 4. Preincubation of ubiquinone-deficient particles with ubiquinone-30 largely restored the NADH-oxidase and NADH-cytochrome b(1)-reductase activities. 5. Various NADH-dye-linked reductases which may be associated with NADH dehydrogenase were not affected by the absence of ubiquinone. 6. The succinate-oxidase complex was less affected than the particulate NADH oxidase by ubiquinone deficiency. 7. A pathway for electrons in the NADH-oxidase complex of the auxotroph of E. coli is proposed and its relationship to the pathway in the wild-type strain is discussed.
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PMID:Ubiquinone deficiency in an auxotroph of Escherichia coli requiring 4-hydroxybenzoic acid. 429 36


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