The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform
Miguel Teixeira - One of the best experts on this subject based on the ideXlab platform.
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A New Type-II NADH Dehydrogenase from the Archaeon Acidianus ambivalens: Characterization and in vitro Reconstitution of the Respiratory Chain
Journal of Bioenergetics and Biomembranes, 2001Co-Authors: Cláudio M. Gomes, Tiago M. Bandeiras, Miguel TeixeiraAbstract:A new type-II NADH Dehydrogenase (NDH-II) was isolated from the hyperthermoacidophilic archaeon Acidianus ambivalens. This enzyme is a monomer with an apparent molecular mass of 47 kDa, containing a covalently bound flavin, and no iron–sulfur clusters. Upon isolation, NDH-II loses activity, which can, nevertheless, be restored by incubation with phospholipids. Catalytically, it is a proficient NADH:caldariella quinone oxidoreductase (130 mmol NADH oxidized/mg protein^-1/min^-1) but it can also donate electrons to synthetic quinones, strongly suggesting its involvement in the respiratory chain. The apparent K_m for NADH was found to be ∼6 μM, both for the purified and membrane-integrated enzyme, thus showing that detergent solubilization and purification did not affect the substrate binding site. Further, it is the first example of a type-II NADH Dehydrogenase that contains the flavin covalently attached, which may be related to the need to stabilize the otherwise labile cofactor in a thermophilic environment. A fully operative minimal version of Acidianus ambivalens respiratory system was successfully reconstituted into artificial liposomes, using three basic components isolated from the organism: the type-II NADH Dehydrogenase, caldariella quinone, the organism-specific quinone, and the aa_3 type quinol oxidase. This system, which mimics the in vivo chain, is efficiently energized by NADH, driving oxygen consumption by means of the terminal oxidase.
Diana S. Beattie - One of the best experts on this subject based on the ideXlab platform.
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External alternative NADH Dehydrogenase of Saccharomyces cerevisiae: a potential source of superoxide.
Free radical biology & medicine, 2003Co-Authors: Jing Fang, Diana S. BeattieAbstract:Three rotenone-insensitive NADH Dehydrogenases are present in the mitochondria of yeast Saccharomyces cerevisiae, which lack complex I. To elucidate the functions of these enzymes, superoxide production was determined in yeast mitochondria. The low levels of hydrogen peroxide (0.10 to 0.18 nmol/min/mg) produced in mitochondria incubated with succinate, malate, or NADH were stimulated 9-fold by antimycin A. Myxothiazol and stigmatellin blocked completely hydrogen peroxide formation with succinate or malate, indicating that the cytochrome bc(1) complex is the source of superoxide; however, these inhibitors only inhibited 46% hydrogen peroxide formation with NADH as substrate. Diphenyliodonium inhibited hydrogen peroxide formation (with NADH as substrate) by 64%. Superoxide formation, determined by EPR and acetylated cytochrome c reduction in mitochondria was stimulated by antimycin A, and partially inhibited by myxothiazol and stigmatellin. Proteinase K digestion of mitoplasts reduced 95% NADH Dehydrogenase activity with a similar inhibition of superoxide production. Mild detergent treatment of the proteinase-treated mitoplasts resulted in an increase in NADH Dehydrogenase activity due to the oxidation of exogenous NADH by the internal NADH Dehydrogenase; however, little increase in superoxide production was observed. These results suggest that the external NADH Dehydrogenase is a potential source of superoxide in S. cerevisiae mitochondria.
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The Presence of Rotenone‐Sensitive NADH Dehydrogenase in the Long Slender Bloodstream and the Procyclic Forms of Trypanosoma Brucei Brucei
European journal of biochemistry, 1996Co-Authors: Diana S. Beattie, Marilyn M. HowtonAbstract:The mitochondrial electron-transport chain present in the procyclic and long slender bloodstream forms of Trypanosoma brucei brucei was investigated by means of several experimental approaches. The oxidation of proline, glycerol and glucose in procyclic cells was inhibited 80–90% by antimycin A or cyanide, 15–19% by salicylhydroxamic acid, and 30–35% by rotenone. Cytochrom-c–reductase activity, with proline or glycerol 3-phosphate as substrate, in a mitochondrial fraction isolated from these cells was inhibited by antimycin and rotenone, but not by malonate, while cytochrome-c–reductase activity with succinate as substrate was inhibited by antimycin A and malonate, but not by rotenone. In addition, the reduction of dichloroindophenol by NADH was inhibited by rotenone but not by malonate, which suggests that rotenone-sensitive NADH Dehydrogenase (complex 1) is present in these mitochondria. The presence of three subunits of NADH Dehydrogenase was observed in immunoblots of mitochondrial proteins with specific antibodies raised against peptides corresponding to predicted antigenic regions of these proteins, which provides further evidence for the presence of NADH Dehydrogenase. In long slender bloodstream forms, the oxidation of glucose or glycerol was inhibited 100% by salicyhydroxamic acid, unaffected by cyanide or antimycin A, and inhibited 40% or 75%, respectively, by rotenone, which suggests that NADH Dehydrogenase is present in these cells. In a mitochondrial fraction isolated from the bloodstream forms, oxygen uptake with glycerol 3-phosphate as substrate was inhibited 65% by rotenone. Low levels of rotenone-sensitive NADH-dependent reduction of dichloroindophenol and the presence of subunits 7 and 8 of NADH Dehydrogenase provided additional evidence for the presence of NADH Dehydrogenase in bloodstream forms of T. brucei.
Dagmar Preis - One of the best experts on this subject based on the ideXlab platform.
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the respiratory chain NADH Dehydrogenase complex i of mitochondria
FEBS Journal, 1991Co-Authors: Hanns Weiss, Thorsten Friedrich, Gotz Hofhaus, Dagmar PreisAbstract:In mitochondria, electrons are transferred from NADH to O2 through a chain of three large enzyme complexes, namely NADH: ubiquinone oxidoreductase (NADH Dehydrogenase or complex I), ubiquinol: ferricytochrome c oxidoreductase (cytochrome reductase or complex III), and ferrocytochrome c:O2 oxidoreductase (cytochrome oxidase or complex IV). The function of these enzyme complexes is to link electron transfer with proton translocation out of the mitochondrion. In doing so, they generate a transmembraneous proton motive force which subsequently drives ATP synthesis by the H+-ATPase (complex V, for a review see [1]).
Gottfried Unden - One of the best experts on this subject based on the ideXlab platform.
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Requirement for the Proton‐Pumping NADH Dehydrogenase I of Escherichia Coli in Respiration of NADH to Fumarate and Its Bioenergetic Implications
European journal of biochemistry, 1997Co-Authors: Quang Hon Tran, Johannes Bongaerts, Dorina Vlad, Gottfried UndenAbstract:In Escherichia coli the expression of the nuo genes encoding the proton pumping NADH Dehydrogenase I is stimulated by the presence of fumarate during anaerobic respiration. The regulatory sites required for the induction by fumarate, nitrate and O2 are located at positions around –309, –277, and downstream of –231 bp, respectively, relative to the transcriptional-start site. The fumarate regulator has to be different from the O2 and nitrate regulators ArcA and NarL. For growth by fumarate respiration, the presence of NADH Dehydrogenase I was essential, in contrast to aerobic or nitrate respiration which used preferentially NADH Dehydrogenase II. The electron transport from NADH to fumarate strongly decreased in a mutant lacking NADH Dehydrogenase I. The mutant used acetyl-CoA instead of fumarate to an increased extent as an electron acceptor for NADH, and excreted ethanol. Therefore, NADH Dehydrogenase I is essential for NADH → fumarate respiration, and is able to use menaquinone as an electron acceptor. NADH → dimethylsulfoxide respiration is also dependent on NADH Dehydrogenase I. The consequences for energy conservation by anaerobic respiration with NADH as a donor are discussed.
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requirement for the proton pumping NADH Dehydrogenase i of escherichia coli in respiration of NADH to fumarate and its bioenergetic implications
FEBS Journal, 1997Co-Authors: Quang Hon Tran, Johannes Bongaerts, Dorina Vlad, Gottfried UndenAbstract:In Escherichia coli the expression of the nuo genes encoding the proton pumping NADH Dehydrogenase I is stimulated by the presence of fumarate during anaerobic respiration. The regulatory sites required for the induction by fumarate, nitrate and O2 are located at positions around –309, –277, and downstream of –231 bp, respectively, relative to the transcriptional-start site. The fumarate regulator has to be different from the O2 and nitrate regulators ArcA and NarL. For growth by fumarate respiration, the presence of NADH Dehydrogenase I was essential, in contrast to aerobic or nitrate respiration which used preferentially NADH Dehydrogenase II. The electron transport from NADH to fumarate strongly decreased in a mutant lacking NADH Dehydrogenase I. The mutant used acetyl-CoA instead of fumarate to an increased extent as an electron acceptor for NADH, and excreted ethanol. Therefore, NADH Dehydrogenase I is essential for NADH → fumarate respiration, and is able to use menaquinone as an electron acceptor. NADH → dimethylsulfoxide respiration is also dependent on NADH Dehydrogenase I. The consequences for energy conservation by anaerobic respiration with NADH as a donor are discussed.
Cláudio M. Gomes - One of the best experts on this subject based on the ideXlab platform.
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A New Type-II NADH Dehydrogenase from the Archaeon Acidianus ambivalens: Characterization and in vitro Reconstitution of the Respiratory Chain
Journal of Bioenergetics and Biomembranes, 2001Co-Authors: Cláudio M. Gomes, Tiago M. Bandeiras, Miguel TeixeiraAbstract:A new type-II NADH Dehydrogenase (NDH-II) was isolated from the hyperthermoacidophilic archaeon Acidianus ambivalens. This enzyme is a monomer with an apparent molecular mass of 47 kDa, containing a covalently bound flavin, and no iron–sulfur clusters. Upon isolation, NDH-II loses activity, which can, nevertheless, be restored by incubation with phospholipids. Catalytically, it is a proficient NADH:caldariella quinone oxidoreductase (130 mmol NADH oxidized/mg protein^-1/min^-1) but it can also donate electrons to synthetic quinones, strongly suggesting its involvement in the respiratory chain. The apparent K_m for NADH was found to be ∼6 μM, both for the purified and membrane-integrated enzyme, thus showing that detergent solubilization and purification did not affect the substrate binding site. Further, it is the first example of a type-II NADH Dehydrogenase that contains the flavin covalently attached, which may be related to the need to stabilize the otherwise labile cofactor in a thermophilic environment. A fully operative minimal version of Acidianus ambivalens respiratory system was successfully reconstituted into artificial liposomes, using three basic components isolated from the organism: the type-II NADH Dehydrogenase, caldariella quinone, the organism-specific quinone, and the aa_3 type quinol oxidase. This system, which mimics the in vivo chain, is efficiently energized by NADH, driving oxygen consumption by means of the terminal oxidase.
