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Kumar R, Jafri MS. Computational Modeling of Mitochondria to Understand the Dynamics of Oxidative Stress. Methods Mol Biol 2022; 2497:363-422. [PMID: 35771458 PMCID: PMC9811848 DOI: 10.1007/978-1-0716-2309-1_27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Mitochondria are complex organelles that use catabolic metabolism to produce ATP which is the critical energy source for cell function. Oxidative phosphorylation by the electron transport chain, which receives reducing equivalents (NADH and FADH2) from the tricarboxylic acid cycle, also produces reactive oxygen species (ROS) as a by-product at complex I and III. ROS play a significant role in health and disease. In order to better understand this process, a computational model of mitochondrial energy metabolism and the production of ROS has been developed. The model demonstrates the process regulating ROS production and removal and how different energy substrates can affect ROS production.
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Affiliation(s)
- Rashmi Kumar
- School of Systems Biology, George Mason University, Fairfax, VA, USA
| | - Mohsin S Jafri
- School of Systems Biology, George Mason University, Fairfax, VA, USA.
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA.
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Szamosvári D, Prothiwa M, Dieterich CL, Böttcher T. Profiling structural diversity and activity of 2-alkyl-4(1H)-quinolone N-oxides of Pseudomonas and Burkholderia. Chem Commun (Camb) 2021; 56:6328-6331. [PMID: 32436549 DOI: 10.1039/d0cc02498h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We synthesized all major saturated and unsaturated 2-alkyl-4(1H)-quinolone N-oxides of Pseudomonas and Burkholderia, quantified their native production levels and characterized their antibiotic activities against competing Staphylococcus aureus. We demonstrate that quinolone core methylation and position of unsaturation in the alkyl-chain dictate antibiotic potency which supports the proposed mechanism of action.
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Affiliation(s)
- Dávid Szamosvári
- Department of Chemistry, Konstanz Research School Chemical Biology, Zukunftskolleg, University of Konstanz, 78457 Konstanz, Germany.
| | - Michaela Prothiwa
- Department of Chemistry, Konstanz Research School Chemical Biology, Zukunftskolleg, University of Konstanz, 78457 Konstanz, Germany.
| | - Cora Lisbeth Dieterich
- Department of Chemistry, Konstanz Research School Chemical Biology, Zukunftskolleg, University of Konstanz, 78457 Konstanz, Germany.
| | - Thomas Böttcher
- Department of Chemistry, Konstanz Research School Chemical Biology, Zukunftskolleg, University of Konstanz, 78457 Konstanz, Germany. and Faculty of Chemistry and Department of Microbiology and Ecosystem Science, University of Vienna, 1090 Vienna, Austria.
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Riccio P, Günther H, Quagliariello E. 2-n-nonyl-4-hydroxy[3-3H]quinoline N-oxide: interaction with the mitochondrial membrane. EUROPEAN JOURNAL OF BIOCHEMISTRY 2005; 114:153-7. [PMID: 7215349 DOI: 10.1111/j.1432-1033.1981.tb06186.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
1. Synthesized 2-n-nonyl-4-hydroxy[3-3H]quinoline N-oxide ([3H]NoHOQnO) is a powerful inhibitor of both NADH oxidase and succinate oxidase activities in submitochondrial particles from beef heart. 2. The binding of [3H]NoHOQnO to submitochondrial particles reveals one specific binding site, which is sensitive to antimycin, and a large amount of aspecific binding. 3. The content of [3H]NoHOQnO-specific binding sites is related to the cytochrome b content in the particles. 4. The binding of [3H]NoHOQnO to the specific site causes the inhibition of electron transfer. 5. The relation between the inhibition of NADH oxidation and [3H]NoHOQnO-specific binding is hyperbolic.
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Isaacson T, Ohad I, Beyer P, Hirschberg J. Analysis in vitro of the enzyme CRTISO establishes a poly-cis-carotenoid biosynthesis pathway in plants. PLANT PHYSIOLOGY 2004; 136:4246-55. [PMID: 15557094 PMCID: PMC535854 DOI: 10.1104/pp.104.052092] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2004] [Revised: 10/16/2004] [Accepted: 10/17/2004] [Indexed: 05/18/2023]
Abstract
Most enzymes in the central pathway of carotenoid biosynthesis in plants have been identified and studied at the molecular level. However, the specificity and role of cis-trans-isomerization of carotenoids, which occurs in vivo during carotene biosynthesis, remained unresolved. We have previously cloned from tomato (Solanum lycopersicum) the CrtISO gene, which encodes a carotene cis-trans-isomerase. To study the biochemical properties of the enzyme, we developed an enzymatic in vitro assay in which a purified tomato CRTISO polypeptide overexpressed in Escherichia coli cells is active in the presence of an E. coli lysate that includes membranes. We show that CRTISO is an authentic carotene isomerase. Its catalytic activity of cis-to-trans isomerization requires redox-active components, suggesting that isomerization is achieved by a reversible redox reaction acting at specific double bonds. Our data demonstrate that CRTISO isomerizes adjacent cis-double bonds at C7 and C9 pairwise into the trans-configuration, but is incapable of isomerizing single cis-double bonds at C9 and C9'. We conclude that CRTISO functions in the carotenoid biosynthesis pathway in parallel with zeta-carotene desaturation, by converting 7,9,9'-tri-cis-neurosporene to 9'-cis-neurosporene and 7'9'-di-cis-lycopene into all-trans-lycopene. These results establish that in plants carotene desaturation to lycopene proceeds via cis-carotene intermediates.
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Affiliation(s)
- Tal Isaacson
- Departments of Genetics , The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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Abstract
The effect of surangin B, an insecticidal natural product coumarin, on presynaptic release of endogenous amino acids was investigated using a purified synaptosomal fraction isolated from mouse brain. Surangin B stimulated the release of glutamic acid (GLU), gamma-aminobutyric acid (GABA), serine, alanine and the aminosulfonic acid taurine from synaptosomes at micromolar concentrations. In all cases, these responses were reduced by removing calcium from the saline and surangin B-evoked release of GLU, GABA, aspartic acid (ASP) and alanine was significantly inhibited by the sodium channel blocker tetrodotoxin. Rotenone (a complex I inhibitor) and carbonyl cyanide chlorophenylhydrazone (CCCP; an uncoupler), were more potent releasers of amino acids from synaptosomes than surangin B, however, carboxin (a complex II-selective inhibitor), was extremely weak to ineffective in this regard. The stimulatory effect of surangin B and complex III-selective inhibitors on release of GLU, GABA, ASP and alanine by synaptosomes was significantly reduced by N,N,N',N'-tetramethyl-p-phenylenediamine, suggesting that blockade of complex III in intraterminal mitochondria is an important effect of this coumarin. Our results demonstrate that surangin B, in common with CCCP and inhibitors of complex I and III, cause release of both neurotransmitter and non-neurotransmitter amino acids from nerve endings in vitro. However, in contrast to most classical agents which interfere selectively with mitochondrial function, the release of endogenous amino acids from synaptosomes by surangin B also involves a moderate extracellular calcium ion-dependent component and relies partially on sodium ion entry into the nerve ending.
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Affiliation(s)
- Yanshen Deng
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
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Braet F, Muller M, Vekemans K, Wisse E, Le Couteur DG. Antimycin A-induced defenestration in rat hepatic sinusoidal endothelial cells. Hepatology 2003; 38:394-402. [PMID: 12883483 DOI: 10.1053/jhep.2003.50347] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
Liver sinusoidal endothelial cells (LSECs) possess fenestrae arranged in sieve plates. Hepatic endothelial fenestrae are open pores approximately 100 to 200 nm in diameter. Alterations in their number or diameter by hormones, xenobiotics, and diseases have important implications for hepatic microcirculation and function. Numerous reports of hepatotoxin-induced defenestration suggest that the cytoskeleton and the energy status of hepatic endothelial cells play a key role in the regulation of fenestrae. Therefore, we investigated the effect of antimycin A, an inhibitor of mitochondrial energy production, on the number of fenestrae in cultured LSECs using high-resolution microscopy and immunocytochemistry. Prolonged incubation (greater than 30 min) with antimycin A resulted in defenestrated cells and coincided with the appearance of F-actin dots, whereas the distribution of G-actin remained unchanged. Adenosine triphosphate (ATP) was depleted dramatically to less than 5% within 30 minutes within the LSECs. After treatment with antimycin A, unusual elevated fenestrated complexes were apparent, organized as a meshwork of anastomosing fenestrae at the center of and above the sieve plates. The position and appearance of these novel structures and their association with defenestration suggest that they are implicated in the process of defenestration. In conclusion, the results of experiments with antimycin A suggest that ATP is needed to maintain fenestrae and the underlying fenestrae-associated cytoskeleton rings that maintain fenestrae patency. Antimycin A-induced defenestration of LSECs is associated with the development of a structure in the sieve plate that appears to be intrinsically involved in defenestration.
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Affiliation(s)
- Filip Braet
- Laboratory for Cell Biology and Histology, Free University of Brussels, Laarbeeklaan, Brussels-Jette, Belgium
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Choi DH, Kim DH, Park YG, Chun BG, Choi SH. Protective effects of rilmenidine and AGN 192403 on oxidative cytotoxicity and mitochondrial inhibitor-induced cytotoxicity in astrocytes. Free Radic Biol Med 2002; 33:1321-33. [PMID: 12419464 DOI: 10.1016/s0891-5849(02)01041-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Oxidative stress and mitochondrial dysfunction are important aspects of pathogenesis, particularly in the brain, which is highly dependent on oxygen, and the protection of astrocytes is essential for neuroprotection. In this context, imidazoline drugs have been reported to be neuroprotective. Our recent study showed that imidazoline drugs, including guanabenz, inhibit the naphthazarin-induced oxidative cytotoxicity associated with lysosomal destabilization. We now report on a study into the protective effects of rilmenidine and AGN 192403, which have affinity for imidazoline-1 receptors, on the cytotoxicity induced by naphthazarin and inhibitors of mitochondrial respiration in astrocytes. Cytotoxicity was measured grossly by LDH release and by measuring changes in lysosomal membrane stability and features of mitochondrial membrane permeabilization. Naphthazarin-induced cytotoxicity was evidenced by the ordered development of lysosomal acridine orange relocation, decrease in mitochondrial potential, cytochrome c release, and caspase-9 activation, and was inhibited by guanabenz, rilmenidine, and AGN 192403. Antimycin A and rotenone induced mitochondrial dysfunction primarily, and their cytotoxicities were inhibited only by AGN 192403. Rilmenidine and guanabenz may have a lysosomal stabilizing effect, which underlies their protective effects. AGN 192403 might affect the mitochondrial cell death cascades, and had a novel protective effect on the cytotoxicity associated with mitochondrial dysfunction.
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Affiliation(s)
- Dong-Hee Choi
- Department of Pharmacology, Korea University College of Medicine, Seoul, South Korea
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Finnegan RB, Carey GB. Characterization of cyclic AMP efflux from swine adipocytes in vitro. OBESITY RESEARCH 1998; 6:292-8. [PMID: 9688106 DOI: 10.1002/j.1550-8528.1998.tb00352.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE A variety of cell types transport cyclic AMP (cAMP) to the extracellular fluid; the purpose of this study was to determine if and how this process occurs in adipocytes. RESEARCH METHODS AND PROCEDURES Adipocytes were isolated from 3-month-old swine and incubated with stimulators of adenylate cyclase for 2 to 120 minutes to promote cAMP synthesis and efflux. Efflux was characterized in the presence of agents that inhibit ATP production, anion transport, intracellular cAMP metabolism, and extracellular cAMP metabolism. Extracellular cAMP was measured by enzyme immunoassay, then corrected for cell lysis by measuring lactate dehydrogenase release. RESULTS cAMP efflux averaged 24.7 fmol/min/cm2 adipocyte surface area, was linear for 2 hours, and was proportional to adipocyte surface area (r=0.94, p<0.05). Efflux was reduced by approximately 35% in cells incubated with 1 microM antimycin, an inhibitor of ATP synthesis (p<0.05), and by approximately 55% in cells incubated with 2 mM probenecid, an anion-specific transport blocker (p<0.05). Extracellular cAMP levels more than doubled by the addition of 1 microM 1,3-dipropyl-8-p-sulfophenylxanthine, a purported inhibitor of extracellular phosphodiesterase. DISCUSSION Our data demonstrate that cAMP is transported from swine adipocytes by an energy-dependent anion transporter and can be metabolized extracellularly. Future studies will evaluate extracellular cAMP as a potential source of extracellular adenosine, a potent inhibitor of adipocyte lipolysis.
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Affiliation(s)
- R B Finnegan
- Department of Animal and Nutritional Sciences, University of New Hampshire, Durham 03824, USA.
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Growth and respiratory oxidation of reduced sulfur compounds by intact cells ofThiobacillus novellus (type strain) grown on thiosulfate. Curr Microbiol 1993. [DOI: 10.1007/bf01576263] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Beffa T, Berczy M, Aragno M. Inhibition of respiratory oxidation of elemental sulfur (S0) and thiosulfate inThiobacillus versutusand another sulfur-oxidizing bacterium. FEMS Microbiol Lett 1992. [DOI: 10.1111/j.1574-6968.1992.tb05138.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Beffa T, Berczy M, Aragno M. Cytochromes and hydrogen-oxidizing activity in the thermophilic hydrogen-oxidizing bacteria related to the genus Hydrogenobacter. Arch Microbiol 1991. [DOI: 10.1007/bf00245398] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Rich PR, Madgwick SA, Moss DA. The interactions of duroquinol, DBMIB and NQNO with the chloroplast cytochrome bf complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1991. [DOI: 10.1016/s0005-2728(05)80252-x] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Papa S, Guerrieri F, Izzo G. The mechanism of proton translocation by the cytochrome system of mitochondria. Characterization of proton-transfer reactions associated with oxidoreductions of terminal respiratory carriers. Biochem J 1983; 216:259-72. [PMID: 6318731 PMCID: PMC1152500 DOI: 10.1042/bj2160259] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A direct kinetic analysis is presented of rapid proton-releasing reactions at the outer or C-side of the membrane, in ox heart and rat liver mitochondria, associated with aerobic oxidation of reduced terminal respiratory carriers in the presence of antimycin. Valinomycin plus K+ enhances the rate of cytochrome c oxidation and the rate and extent of H+ release. In the presence of valinomycin the leads to H+/e- ratio, computed on the basis of total electron flow from respiratory carriers to oxygen, varies with pH, remaining always lower than 1, and is unaffected by N-ethylmaleimide. 2-Heptyl-4-hydroxyquinoline N-oxide and 5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazole, at concentrations which inhibit in the presence of antimycin the oxygen-induced reduction of b cytochromes, cause also a marked depression of the H+ release associated with aerobic oxidation of terminal respiratory carriers. Aerobic oxidation of the cytochrome system in mitochondria and of isolated b-c1 complex and cytochrome c oxidase results in scalar proton release from ionizable groups (redox Bohr effects). In mitochondria and submitochondrial particles, about 70% of the oxidoreductions of the components of the cytochrome system are linked to scalar proton transfer by ionizable groups. In isolated b-c1 complex scalar proton transfer, resulting from redox Bohr effect, amounts to 0.9H+ per Fe-S protein (190 muT). In isolated cytochrome c oxidase, Bohr protons amount to 0.8 per haem a + a3. The results presented indicate that the H+ release from mitochondria during oxidation of terminal respiratory carriers derives from residual antimycin-insensitive electron flow in the quinone-cytochrome c span and from redox Bohr effects in the b-c1 complex and cytochrome c oxidase. There is no sign of proton pumping by cytochrome oxidase during its transition from the reduced to the active 'pulsed' state and the first one or two turnovers.
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Electron pathways from H2 to nitrate in Paracoccus denitrificans. Effects of inhibitors of the UQ-cytochrome b region. Arch Microbiol 1983. [DOI: 10.1007/bf00415612] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Papa S, Izzo G, Guerrieri F. On the inhibition of the b-c1 segment on the mitochondrial respiratory chain by quinone analogues and hydroxyquinoline derivatives. FEBS Lett 1982; 145:93-8. [PMID: 6290267 DOI: 10.1016/0014-5793(82)81213-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Halestrap AP. The pathway of electron flow through ubiquinol:cytochrome c oxidoreductase in the respiratory chain. Evidence from inhibition studies for a modified 'Q cycle'. Biochem J 1982; 204:49-59. [PMID: 6288019 PMCID: PMC1158314 DOI: 10.1042/bj2040049] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
1. Cytochrome spectra of the liver and heart mitochondria incubated under various conditions are presented to compare the effects of antimycin, colletotrichin and 2-heptyl-4-hydroxyquinoline N-oxide (HQNO) additions. 2. Under aerobic conditions, in State 4, in the presence of uncoupler or in the presence of cyanide, all three inhibitors caused oxidation of cytochromes c and c1, but different changes in the spectra of the b cytochromes. Antimycin caused oxidation of a peak at 558 nm and reduction of peaks at 562 nm and 566 nm, whereas colletotrichin caused reduction of peaks at 558 nm and 566 nm and oxidation at 562 nm. HQNO had an effect on the spectra intermediate between those of the two other inhibitors. 3. Under aerobic conditions in the presence of 5 mM-succinate and 5 mM-fumarate, antimycin caused reduction of a peak at 566 nm and oxidation of a peak at 558 nm, whereas colletotrichin had the reverse effect and HQNO caused reduction of a peak at 562 nm. 4. Colletotrichin inhibition of the ADP-stimulated oxidation of glutamate + malate was enhanced by succinate addition and declined again with rotenone addition. Similar but smaller effects were seen with inhibition by antimycin and HQNO. 5. Cytochrome spectra are shown of the effects of ADP and uncoupler addition to stimulate respiration progressively. 6. The results are interpreted in terms of a modified 'Q cycle' [Mitchell (1976) J. Theor. Biol. 62, 327-367] in which the three inhibitors are postulated to displace ubiquinone and ubisemiquinone specifically bound to cytochromes b on both sides of the membrane. 7. It is suggested that cytochromes b558 and b566 are the same b cytochrome located on the outer surface of the membrane, but binding ubisemiquinone or colletotrichin and ubiquinone or antimycin respectively. Cytochrome b562 is postulated to be on the inner surface of the mitochondrial membrane and to bind either ubiquinone or ubisemiquinone, HQNO would bind to the reduced form of the cytochrome and colletotrichin to the oxidized form. 8. Sites for the locus of action of glucagon and the protonmotive force on electron flow are suggested.
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Riccio P, Bobba A, Quagliariello E. Characterization of [3H]NoHOQnO binding to purified complex III. FEBS Lett 1982; 137:222-6. [PMID: 6277692 DOI: 10.1016/0014-5793(82)80354-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Van Ark G, Raap AK, Berden JA, Slater EC. Kinetics of cytochrome b reduction in submitochondrial particles. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 637:34-42. [PMID: 7284355 DOI: 10.1016/0005-2728(81)90207-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
(1) In agreement with Eisenbach and Gutman (Eisenbach, M. and Gutman, M. (1975) Eur. J. Biochem. 52, 107--116) the reduction of cytochrome b in beef-heart submitochondrial particles by succinate in the presence of antimycin was found to be biphasic, the relative amounts of fast and slow phases being dependent on the redox state of a compound located on the oxygen side of the antimycin block. (2) HQNO is a concentration sufficiently large to saturate the specific antimycin- and HQNO-binding sites can substitute for antimycin in these experiments. (3) The rate of the slow phase of the reduction of cytochrome b is decreased under anaerobic conditions and after pretreatment with 2,3-dimercaptopropanol (BAL). (4) In the presence of antimycin and cyanide, cytochrome b-562 is, to some extent, preferentially reduced in the rapid phase and b-566 in the slow phase. (5) The previously proposed regulatory effects of redox-sensitive components X and Y on the redox level and reduction kinetics, respectively, of cytochrome b are ascribed to the role of the Fe-S protein, when it is oxidized, in producing the reductant of cytochrome b by oxidation of QH2, and by the fact that when QH2 is bound to it, the reduced Fe-S protein cannot be oxidized by its natural oxidant, cytochrome c.
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Trumpower BL. New concepts on the role of ubiquinone in the mitochondrial respiratory chain. J Bioenerg Biomembr 1981; 13:1-24. [PMID: 7014553 DOI: 10.1007/bf00744743] [Citation(s) in RCA: 158] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Ubiquinone participates in the oxidation-reduction reactions of the mitochondrial respiratory chain. In addition, this molecule possesses the necessary properties to function as a hydrogen carrier, thereby stoichiometrically coupling proton translocation to respiration by a direct chemiosmotic mechanism. This review discusses recent experimental evidence and new concepts relating to ubiquinone function in the mitochondrial respiratory chain. Emphasis is placed on possible protonmotive mechanisms of ubiquinone function, recent evidence implicating stable forms of ubisemiquinone in the respiratory chain, and properties of the ubiquinone molecule which may relate to its biological function.
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Papa S, Guerrieri F, Lorusso M, Izzo G, Boffoli D, Capuano F, Capitanio N, Altamura N. The H+/e- stoicheiometry of respiration-linked proton translocation in the cytochrome system of mitochondria. Biochem J 1980; 192:203-18. [PMID: 6272694 PMCID: PMC1162323 DOI: 10.1042/bj1920203] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
1. The -->H(+)/e(-) quotients for proton release from mitochondria associated with electron flow from succinate and duroquinol to O(2), ferricyanide or ferricytochrome c, and from NNN'N'-tetramethyl-p-phenylenediamine+ascorbate to O(2), were determined from rate measurements of electron flow and proton translocation. 2. Care was taken to avoid, or to take into account, unrelated electron flow and proton translocation, which might take place in addition to the oxido-reductions that were the subject of our analysis. Spectrophotometric techniques were chosen to provide accurate measurement of the rate of consumption of oxidants and reductants. The rate of proton translocation was measured with fast pH meters with a precision of 10(-3) pH unit. 3. The -->H(+)/O quotient for succinate or duroquinol oxidation was, at neutral pH, 4, when computed on the basis of spectrophotometric determinations of the rate of O(2) consumption or duroquinol oxidation. Higher -->H(+)/O quotients for succinate oxidation, obtained from polarographic measurements of O(2) consumption, resulted from underestimation of the respiratory rate. 4. The -->H(+)/2e(-) quotient for electron flow from succinate and duroquinol to ferricyanide or ferricytochrome c ranged from 3.9 to 3.6. 5. Respiration elicited by NNN'N'-tetramethyl-p-phenylenediamine+ascorbate by antimycin-inhibited mitochondria resulted in extra proton release in addition to that produced for oxidation of ascorbate to dehydroascorbate. Accurate spectrophotometric measurement of respiration showed that the -->H(+)/e(-) ratio was only 0.25 and not 0.7-1.0 as obtained with the inadequate polarographic assay of respiration. Proton release was practically suppressed when mitochondria were preincubated aerobically in the absence of antimycin. Furthermore, the rate of scalar proton consumption for water production was lower than that expected from the stoicheiometry. Thus the extra proton release observed during respiration elicited by NNN'N'-tetramethyl-p-phenylenediamine+ascorbate is caused by oxidation of endogenous hydrogenated reductants. 6. It is concluded that (i) the -->H(+)/O quotient for the cytochrome system is, at neutral pH, 4 and not 6 or 8 as reported by others; (ii) all the four protons are released during electron flow from quinol to cytochrome c; (iii) the oxidase transfers electrons from cytochrome c to protons from the matrix aqueous phase and does not pump protons from the matrix to the outer aqueous phase.
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Doussière J, Sainsard-Chanet A, Vignais PV. The respiratory chain of Paramecium tetraurelia in wild type and the mutant Cl1. II. Cyanide-insensitive respiration. Function and regulation. BIOCHIMICA ET BIOPHYSICA ACTA 1979; 548:236-52. [PMID: 41573 DOI: 10.1016/0005-2728(79)90132-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
1. The cyanide-insensitive respiration in Paramecium tetraurelia was found to be located in mitochondria. 2. Sensitivity of the mitochondrial respiration to cyanide depended on growth conditions. Under standard conditions of growth, 15--20% of respiration was insensitive to 1 mM cyanide. Full resistance to 1 mM cyanide was observed by growing cells in the presence of erythromycin (100--400 microgram/ml) 0.2 mM cyanide. The mitochondrial respiration of the mutant Cl1 harvested during the exponential phase of growth was largely insensitive to cyanide (more than 80%). 3. Pyruvate was oxidized at the same rate by wild type mitochondria and mitochondria of the mutant Cl1. In contrast, succinate oxidation was 2--3 times faster in mitochondria of the mutant Cl1 than in wild type mitochondria. 4. The cyanide-insensitive respiration was inhibited by 1 mM salicylhydroxamic acid to nearly 100%. Other efficient respiratory inhibitors included amytal and heptylhydroxyquinoline. Antimycin was not inhibitory even at concentrations as high as 5 microgram/mg protein, a finding consistent with the lack of antimycin binding sites.
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