Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.6.5.3 (complex I)
8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Data on succinate-ubiquinone reductase are critically reviewed. The structural and catalytic properties of succinate dehydrogenase and succinate-ubiquinone reductase are compared. The redox components, active centers and proteins involved in the enzyme interaction with ubiquinone are described. Some structural and kinetic features of the succinate-ubiquinone reductase as the respiratory chain component and feasible mechanisms of regulation of the succinate-ubiquinone reductase activity are discussed.
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PMID:[Succinate-ubiquinone reductase site of the respiratory chain]. 354 59

Experimental evidence is presented showing the existence of an NADH-consuming enzyme in heart mitochondria, in addition to the NADH--ubiquinone oxidase of complex I. In contrast to the latter, the novel enzyme is accessible from the extramitochondrial space. Removal of the outer membranes from intact mitochondria had no influence on exogenous NADH consumption, indicating its location at the cytosolic face of the inner membrane. The enzyme could be solubilized from this membrane and purified by sedimentation through preformed sucrose gradients. Liver mitochondria exhibited no oxidation of external NADH, suggesting that the enzyme is organo-specific. The "exogenous NADH dehydrogenase" of heart mitochondria was found to introduce reducing equivalents into the respiratory chain before the rotenone block, indicating that the enzyme is associated with complex I. The enzyme was also demonstrated to be involved in electron flow from the respiratory chain to exogenous electron acceptors, including NAD+. This permitted us to elicit the existence of an energy-dependent reversed electron flow from complex II to complex I. The redox shuttle established by the novel enzyme could be of significance for the regulation of cellular NADH and the metabolic activation of foreign compounds such as adriamycin.
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PMID:Demonstration of the existence of an organo-specific NADH dehydrogenase in heart mitochondria. 369 7

The inhibitory effect of pyridoxal phosphate on the Triton X-100 solubilized purified bovine heart succinate-ubiquinone reductase (Choudhry, Z.M., Gavrikova, E.V., Kotlyar, A.B., Tushurashvilli, P.R. and Vinogradov, A.D. (1985) FEBS Lett. 182, 171-175) was studied. The kinetics of the enzyme inactivation by pyridoxal phosphate was found to be strongly dependent both qualitatively and quantitatively on the concentration of the protein-detergent complexes. In the diluted system the inactivation of the ubiquinone-depleted enzyme was completely prevented by the saturating concentrations of Q2, carboxin, thenoiltrifluoroacetone and pentachlorophenol, i.e., by the substrate and specific inhibitors of the enzyme. The protective effects of Q2 and the inhibitors was employed to quantitate the affinities of the ligands to their specific binding sites. Strong difference in the affinity of Q2 to the reduced and oxidized enzyme was found. When the soluble reconstitutively active succinate dehydrogenase was treated with pyridoxal phosphate, the reactivity of the enzyme towards low ferricyanide concentrations and its reconstitutive activity was significantly protected against aerobic inactivation.
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PMID:Studies on the succinate dehydrogenating system. Interaction of the mitochondrial succinate-ubiquinone reductase with pyridoxal phosphate. 370 47

Bovine heart mitochondrial NADH----ubiquinone reductase (complex I), contains two disulfide-linked subunits of 75 and 33 kDa as revealed by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis with beta-mercaptoethanol omitted from preparation of the sample for the first dimension. Two unidentified polypeptides (110-115 and 69 kDa) are also found in disulfide linkage with the two complex I subunits. The 110-115-kDa polypeptide appears to be pyridine dinucleotide transhydrogenase by several criteria including selective precipitation with an antibody raised to the purified transhydrogenase. The two disulfide-linked subunits were also found in a product cross-linked for 2 min with dithiobis (succinimidyl propionate) (DSP) along with five other complex I subunits of 53-57, 42, 24-27, 17-18, and 12.5-15.5 kDa (Gondal, J.A., and Anderson, W.M. (1985) J. Biol. Chem. 260, 5931-5935) indicating that these seven subunits lie within 11-12 A of each other at one or more points in space in the enzyme's interior. Cross-linking of complex I with DSP for 2 min in the presence of 1 microM rotenone yielded a cross-linked product consisting of the two natural disulfide-linked subunits and the 110-115- and 69-kDa polypeptides. This suggests that rotenone induces a conformational change in the enzyme that moves the seven DSP cross-linked subunits away from each other and outside the 11-12 A bridging distance of DSP. This alteration in conformation may be communicated to iron-sulfur center N-2 within the hydrophobic outer shell of the enzyme to prevent electron transfer to its natural electron acceptor, ubiquinone. A model of rotenone action based upon these observations is presented.
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PMID:The molecular morphology of bovine heart mitochondrial NADH----ubiquinone reductase. Native disulfide-linked subunits and rotenone-induced conformational changes. 393 May 1

Treatment of the soluble ubiquinone-deficient succinate: ubiquinone reductase with pyridoxal phosphate results in the inhibition of the carboxin-sensitive ubiquinone-reductase activity of the enzyme. The inactivation is prevented by the soluble homolog of ubiquinone (Q2) but is insensitive to the dicarboxylates interacting with the substrate binding site of succinate dehydrogenase. The reactivity of the pyridoxal phosphate-inhibited enzyme with different electron acceptors suggests that the observed inhibition is due to the dissociation of succinate dehydrogenase from the enzyme complex. The soluble succinate dehydrogenase was recovered in the supernatant after treatment of the insoluble succinate: ubiquinone reductase with pyridoxal phosphate. The data obtained strongly suggest the participation of amino groups in the interaction between succinate dehydrogenase and the ubiquinone reactivity conferring peptide within the complex.
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PMID:Pyridoxal phosphate-induced dissociation of the succinate: ubiquinone reductase. 397 21

The cationic fluorescent dyes, berberines, have been observed to inhibit NAD-linked respiration in rat liver mitochondria. Low concentrations inhibit electron transport in the NAD-ubiquinone span after penetration into mitochondria. More hydrophobic alkyl derivatives proved to be stronger inhibitors showing more rapid onset of inhibition. The inhibition was totally dependent on the energization of the membrane; however, the addition of a hydrophobic anion stimulated the inhibition effects in uncoupled mitochondria. Substantially higher concentrations of berberines are needed for the inhibition of the oxidation of succinate. The excess of dye interacting with surface dipoles in the energized state can inhibit the energy transduction through the complex bc1. On the basis of the difference in the rate of fluorescence response when berberines are added to coupled mitochondria and the corresponding inhibition effects, the presence minimally of two binding sites was suggested. The dye bound on the outer surface is highly fluorescent and inhibits the energy transduction if added in excess. The remaining dye interacting with NADH dehydrogenase does not fluoresce. The accumulation of alkylberberine in mitochondria results in additional effects in the region of cytochrome b the nature of which is not fully understood.
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PMID:Interaction of fluorescent berberine alkyl derivatives with respiratory chain of rat liver mitochondria. 398 24

Thenoyltrifluoroacetone (TTA) and carboxin inhibit soluble ubiquinone-deficient succinate: ubiquinone reductase according to the mixed type (with respect to added Q2) inhibition. pattern. The Ki values for the inhibitors are mutually dependent, thus indicating the presence of a single binding site for both TTA and carboxin. The enolic form of TTA was shown to be the species interacting with the enzyme. Carboxin prevents the alkali-induced inactivation of the membrane-bound succinate dehydrogenase without having any effect on the reconstitution of succinate: ubiquinone reductase from the soluble dehydrogenase and b-c1 complex. The reduction of the respiratory chain by succinate protects succinate dehydrogenase against inactivation (solubilization) by alkali; under these conditions, carboxin does not affect the inactivation process. The cumulative data suggest that the degree of the mutual mobility of the succinate dehydrogenase smaller subunit and ubiquinone reactivity-conferring protein (QPs) is a prerequisite for the catalytic mechanism of succinate: ubiquinone reductase. A mechanism of the enzyme inhibition by TTA and carboxin is proposed, which consists in non-covalent cross-linking of the subunits by the inhibitors.
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PMID:[Interaction of mitochondrial succinate:ubiquinone reductase with thenoyltrifluoroacetone and carboxin]. 399 1

Measurements were made of the stoicheiometry of proton-translocation coupled to NAD(P)H oxidation by several quinones (duroquinone, ubiquinone(0), ubiquinone(1), ubiquinone(2)) in mitochondria from rat liver and ox heart. Observed stoicheiometries of protons translocated per mol of NADH oxidized (-->H(+)/2e(-) ratios; Mitchell, 1966) ranged from 0.75 (rat liver mitochondria with ubiquinone(1)) to 1.55 (ox heart mitochondria with ubiquinone(1) or ubiquinone(2)). Only the rotenone-sensitive pathway of NADH oxidation by quinone was able to support proton translocation. Correction of the observed -->H(+)/2e(-) ratios for the loss of reducing equivalents to the rotenone-insensitive pathway increased their value to approx. 2.0. It is concluded that the rotenone-sensitive NADH- ubiquinone reductase activity of the respiratory chain may be organized in the mitochondrial membrane as a proton-translocating oxidoreduction loop. The number of such loops between NADH and ubiquinone is one, and not two, as initially proposed by Mitchell (1966).
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PMID:Proton translocation coupled to quinone reduction by reduced nicotinamide--adenine dinucleotide in rat liver and ox heart mitochondria. 414 94

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

1. A spectroscopic resolution has been made of the components contributing to the ;iron-flavoprotein' trough extending from 450 to 520nm in the reduced-minus-oxidized difference spectrum of submitochondrial particles of Torulopsis utilis. 2. Seven components were identified other than cytochrome b, ubiquinone and succinate dehydrogenase. On the basis of the effects of iron- and sulphate-limited growth of cells on their subsequently derived electron-transport particles, and also by consideration of analytical measurements of the concentration of FMN, FAD, non-haem iron and acid-labile sulphide in the electron-transport particles in relation to the magnitude of the spectroscopic changes, it was possible to identify five of these components as follows: species 1a, the flavin of NADH dehydrogenase ferroflavoprotein; species 1b, the iron-sulphur component of NADH dehydrogenase ferroflavoprotein; species 1', the flavin of an NADPH dehydrogenase; species 2, an iron-sulphur or ferroflavoprotein component; species 3, the flavin of l-3-glycerophosphate dehydrogenase. Two additional components were a fluorescent flavoprotein, probably lipoamide dehydrogenase, and a b-type cytochrome reducible by NADH or NADPH but not reoxidizable by the respiratory chain. 3. Species 1b and 2 were undetectable in electron-transport particles from iron- or sulphate-limited cells, but could be recovered in vivo under non-growing conditions. 4. The recovery in vivo of species 2 but not species 1b was inhibited by cycloheximide. 5. The recovery of species 1b correlates with the recovery of site 1 conservation. 6. The recovery of species 1b with species 2 correlates with the recovery of piericidin A sensitivity. 7. Evidence is presented for an NADPH dehydrogenase distinct from NADH dehydrogenase. The oxidation of NADH and NADPH by the respiratory chain is sensitive to piericidin A, and an iron-sulphur protein common to both pathways (species 2) is suggested as the piericidin A-sensitive component. 8. The approximate E'(0) (pH7.0) values of species 1 (a and b, low potential) and species 2 (high potential) indicate that site 1 energy conservation occurs between the levels of species 1 (a and b) and species 2.
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PMID:Spectroscopic studies of flavoproteins and non-haem iron proteins of submitochondrial particles of Torulopsis utilis modified by iron- and sulphate-limited growth in continuous culture. 439 18


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