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Bénit P, Goncalves J, El Khoury R, Rak M, Favier J, Gimenez-Roqueplo AP, Rustin P. Succinate Dehydrogenase, Succinate, and Superoxides: A Genetic, Epigenetic, Metabolic, Environmental Explosive Crossroad. Biomedicines 2022; 10:biomedicines10081788. [PMID: 35892689 PMCID: PMC9394281 DOI: 10.3390/biomedicines10081788] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 07/18/2022] [Accepted: 07/22/2022] [Indexed: 11/16/2022] Open
Abstract
Research focused on succinate dehydrogenase (SDH) and its substrate, succinate, culminated in the 1950s accompanying the rapid development of research dedicated to bioenergetics and intermediary metabolism. This allowed researchers to uncover the implication of SDH in both the mitochondrial respiratory chain and the Krebs cycle. Nowadays, this theme is experiencing a real revival following the discovery of the role of SDH and succinate in a subset of tumors and cancers in humans. The aim of this review is to enlighten the many questions yet unanswered, ranging from fundamental to clinically oriented aspects, up to the danger of the current use of SDH as a target for a subclass of pesticides.
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Affiliation(s)
- Paule Bénit
- NeuroDiderot, Inserm, Université Paris Cité, F-75019 Paris, France; (P.B.); (M.R.)
| | - Judith Goncalves
- Paris Centre de Recherche Cardiovasculaire (PARCC), Inserm, Université Paris Cité, F-75015 Paris, France; (J.G.); (J.F.)
| | - Riyad El Khoury
- Department of Pathology and Laboratory Medicine, Neuromuscular Diagnostic Laboratory, American University of Beirut Medical Center, Beirut 1107 2020, Lebanon;
| | - Malgorzata Rak
- NeuroDiderot, Inserm, Université Paris Cité, F-75019 Paris, France; (P.B.); (M.R.)
| | - Judith Favier
- Paris Centre de Recherche Cardiovasculaire (PARCC), Inserm, Université Paris Cité, F-75015 Paris, France; (J.G.); (J.F.)
| | - Anne-Paule Gimenez-Roqueplo
- Département de Médecine Génomique des Tumeurs et des Cancers, Assistance Publique-Hôpitaux de Paris (AP-HP), Hôpital Européen Georges Pompidou, F-75015 Paris, France;
| | - Pierre Rustin
- NeuroDiderot, Inserm, Université Paris Cité, F-75019 Paris, France; (P.B.); (M.R.)
- Correspondence:
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2
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Wright JJ, Biner O, Chung I, Burger N, Bridges HR, Hirst J. Reverse Electron Transfer by Respiratory Complex I Catalyzed in a Modular Proteoliposome System. J Am Chem Soc 2022; 144:6791-6801. [PMID: 35380814 PMCID: PMC9026280 DOI: 10.1021/jacs.2c00274] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Indexed: 02/02/2023]
Abstract
Respiratory complex I is an essential metabolic enzyme that uses the energy from NADH oxidation and ubiquinone reduction to translocate protons across an energy transducing membrane and generate the proton motive force for ATP synthesis. Under specific conditions, complex I can also catalyze the reverse reaction, Δp-linked oxidation of ubiquinol to reduce NAD+ (or O2), known as reverse electron transfer (RET). Oxidative damage by reactive oxygen species generated during RET underpins ischemia reperfusion injury, but as RET relies on several converging metabolic pathways, little is known about its mechanism or regulation. Here, we demonstrate Δp-linked RET through complex I in a synthetic proteoliposome system for the first time, enabling complete kinetic characterization of RET catalysis. We further establish the capability of our system by showing how RET in the mammalian enzyme is regulated by the active-deactive transition and by evaluating RET by complex I from several species in which direct assessment has not been otherwise possible. We thus provide new insights into the reversibility of complex I catalysis, an important but little understood mechanistic and physiological feature.
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Affiliation(s)
- John J. Wright
- Medical Research Council
Mitochondrial Biology Unit, University of
Cambridge, Cambridge CB2 0XY, U.K.
| | | | - Injae Chung
- Medical Research Council
Mitochondrial Biology Unit, University of
Cambridge, Cambridge CB2 0XY, U.K.
| | | | - Hannah R. Bridges
- Medical Research Council
Mitochondrial Biology Unit, University of
Cambridge, Cambridge CB2 0XY, U.K.
| | - Judy Hirst
- Medical Research Council
Mitochondrial Biology Unit, University of
Cambridge, Cambridge CB2 0XY, U.K.
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3
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Chung I, Serreli R, Cross JB, Di Francesco ME, Marszalek JR, Hirst J. Cork-in-bottle mechanism of inhibitor binding to mammalian complex I. SCIENCE ADVANCES 2021; 7:7/20/eabg4000. [PMID: 33990335 PMCID: PMC8121435 DOI: 10.1126/sciadv.abg4000] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 03/26/2021] [Indexed: 05/08/2023]
Abstract
Mitochondrial complex I (NADH:ubiquinone oxidoreductase), a major contributor of free energy for oxidative phosphorylation, is increasingly recognized as a promising drug target for ischemia-reperfusion injury, metabolic disorders, and various cancers. Several pharmacologically relevant but structurally unrelated small molecules have been identified as specific complex I inhibitors, but their modes of action remain unclear. Here, we present a 3.0-Å resolution cryo-electron microscopy structure of mammalian complex I inhibited by a derivative of IACS-010759, which is currently in clinical development against cancers reliant on oxidative phosphorylation, revealing its unique cork-in-bottle mechanism of inhibition. We combine structural and kinetic analyses to deconvolute cross-species differences in inhibition and identify the structural motif of a "chain" of aromatic rings as a characteristic that promotes inhibition. Our findings provide insights into the importance of π-stacking residues for inhibitor binding in the long substrate-binding channel in complex I and a guide for future biorational drug design.
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Affiliation(s)
- Injae Chung
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Riccardo Serreli
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Jason B Cross
- Institute for Applied Cancer Science (IACS), The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA
| | - M Emilia Di Francesco
- Institute for Applied Cancer Science (IACS), The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA
| | - Joseph R Marszalek
- TRACTION-Translational Research to AdvanCe Therapeutics and Innovation in ONcology, The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA
| | - Judy Hirst
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK.
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4
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Thompson BL, Heiden ZM. Tuning the reduction potentials of benzoquinone through the coordination to Lewis acids. Phys Chem Chem Phys 2021; 23:9822-9831. [PMID: 33908513 DOI: 10.1039/d1cp01266e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Electron transfer promoted by the coordination of a substrate molecule to a Lewis acid or hydrogen bonding group is a critical step in many biological and catalytic transformations. This computational study investigates the nature of the interaction between benzoquinone and one and two Lewis acids by examining the influence of Lewis acid strength on the ability to alter the two reduction potentials of the coordinated benzoquinone molecule. To investigate this interaction, the coordination of the neutral (Q), singly reduced ([Q]˙-), and doubly reduced benzoquinone ([Q]2-) molecule to eight Lewis acids was analyzed. Coordination of benzoquinone to a Lewis acid became more favorable by 25 kcal mol-1 with each reduction of the benzoquinone fragment. Coordination of benzoquinone to a Lewis acid also shifted each of the reduction potentials of the coordinated benzoquinone anodically by 0.50 to 1.5 V, depending on the strength of the Lewis acid, with stronger Lewis acids exhibiting a larger effect on the reduction potential. Coordination of a second Lewis acid further altered each of the reduction potentials by an additional 0.70 to 1.6 V. Replacing one of the Lewis acids with a proton resulted in the ability to modify the pKa of the protonated Lewis acid-Q/[Q]˙-/[Q]2- adducts by about 10 pKa units, in addition to being able to alter the ability to transfer a hydrogen atom by 10 kcal mol-1, and the capacity to transfer a hydride by about 30 kcal mol-1.
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Affiliation(s)
- Brena L Thompson
- Department of Chemistry, Washington State University, Pullman, Washington 99164, USA.
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5
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Abstract
Respiratory complex I (NADH:ubiquinone oxidoreductase) captures the free energy from oxidising NADH and reducing ubiquinone to drive protons across the mitochondrial inner membrane and power oxidative phosphorylation. Recent cryo-EM analyses have produced near-complete models of the mammalian complex, but leave the molecular principles of its long-range energy coupling mechanism open to debate. Here, we describe the 3.0-Å resolution cryo-EM structure of complex I from mouse heart mitochondria with a substrate-like inhibitor, piericidin A, bound in the ubiquinone-binding active site. We combine our structural analyses with both functional and computational studies to demonstrate competitive inhibitor binding poses and provide evidence that two inhibitor molecules bind end-to-end in the long substrate binding channel. Our findings reveal information about the mechanisms of inhibition and substrate reduction that are central for understanding the principles of energy transduction in mammalian complex I. The respiratory complex I (NADH:ubiquinone oxidoreductase) is a large redox-driven proton pump that initiates respiration in mitochondria. Here, the authors present the 3.0 Å cryo-EM structure of complex I from mouse heart mitochondria with the ubiquinone-analogue inhibitor piericidin A bound in the active site and with kinetic measurements and MD simulations they further show that this inhibitor acts competitively against the native ubiquinone-10 substrate.
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6
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Zhang L, Xu Y, Makris TM, Wang Q. Enhanced Arylamine N-Oxygenase Activity of Polymer–Enzyme Assemblies by Facilitating Electron-Transferring Efficiency. Biomacromolecules 2018; 19:918-925. [DOI: 10.1021/acs.biomac.7b01706] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Libo Zhang
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
| | - Yanmei Xu
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
| | - Thomas M. Makris
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
| | - Qian Wang
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
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7
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Bernhard Y, Gigot E, Goncalves V, Moreau M, Sok N, Richard P, Decréau RA. Direct subphthalocyanine conjugation to bombesin vs. indirect conjugation to its lipidic nanocarrier. Org Biomol Chem 2018; 14:4511-8. [PMID: 27097718 DOI: 10.1039/c6ob00530f] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Bombesin (BBN) was covalently bound to graftable subphthalocyanine (SubPc) or to a cholesterol derivative, a component of a liposome that encapsulates non-graftable SubPc. The latter bioconjugation approach was suitable to address the stability of SubPc and was achieved by copper-free click-chemistry on the outer-face of the liposome. Liposomes were purified (FPLC) and then analyzed in size (outer diameter about 60 nm measured by DLS). In vitro binding studies allowed to determine the IC50 13.9 nM for one component of the liposome, cholesterol, conjugated to BBN. Hence, azido- (or alkynyl-) liposomes give fluorophores with no reactive functional group available on their backbone a second chance to be (indirectly) bioconjugated (with bombesin).
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Affiliation(s)
- Yann Bernhard
- ICMUB Institute-Dept of Chemistry, Sciences Mirande, UMR-CNRS 6302, 9 Avenue Alain Savary, University of Burgundy Franche-Comté, France.
| | - Elodie Gigot
- ICMUB Institute-Dept of Chemistry, Sciences Mirande, UMR-CNRS 6302, 9 Avenue Alain Savary, University of Burgundy Franche-Comté, France.
| | - Victor Goncalves
- ICMUB Institute-Dept of Chemistry, Sciences Mirande, UMR-CNRS 6302, 9 Avenue Alain Savary, University of Burgundy Franche-Comté, France.
| | - Mathieu Moreau
- ICMUB Institute-Dept of Chemistry, Sciences Mirande, UMR-CNRS 6302, 9 Avenue Alain Savary, University of Burgundy Franche-Comté, France.
| | - Nicolas Sok
- AgroSup Dijon, UMR PAM, 1 Esplanade Erasme, University Bourgogne Franche-Comté, 21078 Dijon, France
| | - Philippe Richard
- ICMUB Institute-Dept of Chemistry, Sciences Mirande, UMR-CNRS 6302, 9 Avenue Alain Savary, University of Burgundy Franche-Comté, France.
| | - Richard A Decréau
- ICMUB Institute-Dept of Chemistry, Sciences Mirande, UMR-CNRS 6302, 9 Avenue Alain Savary, University of Burgundy Franche-Comté, France.
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8
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Lancaster CRD, Betz YM, Heit S, Lafontaine MA. Transmembrane Electron and Proton Transfer in Diheme-Containing Succinate : Quinone Oxidoreductases. Isr J Chem 2017. [DOI: 10.1002/ijch.201600139] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- C. Roy D. Lancaster
- Department of Structural Biology; Center of Human and Molecular Biology (ZHMB); Saarland University; Faculty of Medicine Building 60 D-66421 Homburg (Saar) Germany
| | - Yamila M. Betz
- Department of Structural Biology; Center of Human and Molecular Biology (ZHMB); Saarland University; Faculty of Medicine Building 60 D-66421 Homburg (Saar) Germany
| | - Sabine Heit
- Department of Structural Biology; Center of Human and Molecular Biology (ZHMB); Saarland University; Faculty of Medicine Building 60 D-66421 Homburg (Saar) Germany
| | - Michael A. Lafontaine
- Department of Structural Biology; Center of Human and Molecular Biology (ZHMB); Saarland University; Faculty of Medicine Building 60 D-66421 Homburg (Saar) Germany
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9
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Rak M, Bénit P, Chrétien D, Bouchereau J, Schiff M, El-Khoury R, Tzagoloff A, Rustin P. Mitochondrial cytochrome c oxidase deficiency. Clin Sci (Lond) 2016; 130:393-407. [PMID: 26846578 PMCID: PMC4948581 DOI: 10.1042/cs20150707] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
As with other mitochondrial respiratory chain components, marked clinical and genetic heterogeneity is observed in patients with a cytochrome c oxidase deficiency. This constitutes a considerable diagnostic challenge and raises a number of puzzling questions. So far, pathological mutations have been reported in more than 30 genes, in both mitochondrial and nuclear DNA, affecting either structural subunits of the enzyme or proteins involved in its biogenesis. In this review, we discuss the possible causes of the discrepancy between the spectacular advances made in the identification of the molecular bases of cytochrome oxidase deficiency and the lack of any efficient treatment in diseases resulting from such deficiencies. This brings back many unsolved questions related to the frequent delay of clinical manifestation, variable course and severity, and tissue-involvement often associated with these diseases. In this context, we stress the importance of studying different models of these diseases, but also discuss the limitations encountered in most available disease models. In the future, with the possible exception of replacement therapy using genes, cells or organs, a better understanding of underlying mechanism(s) of these mitochondrial diseases is presumably required to develop efficient therapy.
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Affiliation(s)
- Malgorzata Rak
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
| | - Paule Bénit
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
| | - Dominique Chrétien
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
| | - Juliette Bouchereau
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
| | - Manuel Schiff
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Reference Center for Inherited Metabolic Diseases, Hôpital Robert Debré, Assistance Publique-Hôpitaux de Paris, 48 Boulevard Sérurier, 75019 Paris, France
| | - Riyad El-Khoury
- American University of Beirut Medical Center, Department of Pathology and Laboratory Medicine, Cairo Street, Hamra, Beirut, Lebanon
| | - Alexander Tzagoloff
- Biological Sciences Department, Columbia University, New York, NY 10027, U.S.A
| | - Pierre Rustin
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1141, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France Faculté de Médecine Denis Diderot, Université Paris Diderot-Paris 7, Site Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France
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10
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Bernhard Y, Winckler P, Chassagnon R, Richard P, Gigot É, Perrier-Cornet JM, Decréau RA. Subphthalocyanines: addressing water-solubility, nano-encapsulation, and activation for optical imaging of B16 melanoma cells. Chem Commun (Camb) 2014; 50:13975-8. [DOI: 10.1039/c4cc05503a] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Three new facets of subphthalocyanines (hydrophilic/hydrophobic) are presented: probes for molecular imaging, pH-activation, nano-encapsulation (liposomes: 20 nm large/13% loading).
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Affiliation(s)
- Yann Bernhard
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB)
- UMR 6302 CNRS – Université de Bourgogne
- Dijon Cedex, France
| | - Pascale Winckler
- Université de Bourgogne
- AgroSup Dijon
- Dimacell Imaging Ressource Center
- F-21000 Dijon, France
| | - Remi Chassagnon
- Laboratoire Interdisciplinaire Carnot Bourgogne
- UMR CNRS 6303 – Université de Bourgogne
- F-21078 Dijon, France
| | - Philippe Richard
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB)
- UMR 6302 CNRS – Université de Bourgogne
- Dijon Cedex, France
| | - Élodie Gigot
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB)
- UMR 6302 CNRS – Université de Bourgogne
- Dijon Cedex, France
| | | | - Richard A. Decréau
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB)
- UMR 6302 CNRS – Université de Bourgogne
- Dijon Cedex, France
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11
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Barge J, Decréau R, Julliard M, Hubaud JC, Sabatier AS, Grob JJ, Verrando P. Killing efficacy of a new silicon phthalocyanine in human melanoma cells treated with photodynamic therapy by early activation of mitochondrion-mediated apoptosis. Exp Dermatol 2004; 13:33-44. [PMID: 15009114 DOI: 10.1111/j.0906-6705.2004.00147.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Photodynamic therapy (PDT) is a promising therapeutic modality that utilizes a combination of a photosensitizer and visible light for the destruction of diseased tissues. Using human-pigmented melanoma cells, we examined the photokilling efficacy of new silicon-phthalocyanines (SiPc) that bore bulky axial substituents. The bis(cholesteryloxy) derivate (Chol-O-SiPc) displayed the best in vitro photokilling efficacy (LD(50) = 6-8 x 10(-9) M) and was seven to nine times more potent than chloro-aluminium Pc (ClAlPc), a known photosensitizer used as a reference. Although Chol-O-SiPc was half as potent as ClAlPc for promoting photo-oxidative membrane damage in a cell-free assay, early events of mitochondrion-mediated apoptosis upon PDT were triggered much faster, as demonstrated by kinetics studies examining cells with permeabilized mitochondrial membranes, cytochrome c release and caspase-9 activation. Inhibition of caspase-9 activity by a substrate analogue argued for its central role in the proapoptotic events leading to cell death by Chol-O-SiPc PDT. In addition, immunoblots showed that Bcl-2 antiapoptotic oncoprotein was not a primary target of Chol-O-SiPc in M3Dau cells treated with PDT. Conclusively, Chol-O-SiPc is a useful new photosensitizer with the property of triggering cell apoptosis mediated by mitochondria.
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Affiliation(s)
- Jérôme Barge
- Laboratoire Activation, Mécanismes, Modélisation Moléculaire, ESA CNRS 6009, Faculté des Sciences de Saint Jérôme, Marseille, France
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12
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13
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Moore AL, Dry IB, Wiskich JT. Measurement of the redox state of the ubiquinone pool in plant mitochondria. FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)81237-7] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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14
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Giorgini E, Tommasi G, Stipa P, Tosi G, Littarru G, Greci L. Reactivity of ubiquinones and ubiquinols with free radicals. Free Radic Res 2001; 35:63-72. [PMID: 11697118 DOI: 10.1080/10715760100300601] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The reactivity of quinones 1-4 and of the corresponding quinols 5-8 towards carbon- and oxygen-centred radicals were studied. All quinones bearing at least one nuclear position free, readily react with alkyl and phenyl radicals to afford the alkylated quinones 12-24; however, quinones 1 and 3 reacted with 2-cyano-2-propyl radical to yield products (the mono- and di-ethers 9-11) derived from the attack on the carbonylic oxygen. The reactions carried out on quinones with the benzoyloxy radical led to no reaction products and in the case of Q10, the isoprenic chain also remained unchanged. Quinols 5-8 reacted only with oxygen-centred radicals (benzoyloxy and 2-cyano-2-propyl-peroxy radicals) to give the corresponding quinones. The isoprenic chain of Q10 did not undergo attack even with peroxy radicals. Carbon-centred radicals resulted unable to abstract hydrogen from the studied quinols.
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Affiliation(s)
- E Giorgini
- Dipartimento di Scienze dei Materiali e della Terra, via Brecce Bianche, Università, I-60131 Ancona, Italy
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15
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Affiliation(s)
- V E Kagan
- Department of Environmental and Occupational Health, University of Pittsburgh, Pennsylvania 15238, USA
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16
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Okun JG, Lümmen P, Brandt U. Three classes of inhibitors share a common binding domain in mitochondrial complex I (NADH:ubiquinone oxidoreductase). J Biol Chem 1999; 274:2625-30. [PMID: 9915790 DOI: 10.1074/jbc.274.5.2625] [Citation(s) in RCA: 263] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have developed two independent methods to measure equilibrium binding of inhibitors to membrane-bound and partially purified NADH:ubiquinone oxidoreductase (complex I) to characterize the binding sites for the great variety of hydrophobic compounds acting on this large and complicated enzyme. Taking advantage of a partial quench of fluorescence upon binding of the fenazaquin-type inhibitor 2-decyl-4-quinazolinyl amine to complex I in bovine submitochondrial particles, we determined a Kd of 17 +/- 3 nM and one binding site per complex I. Equilibrium binding studies with [3H]dihydrorotenone and the aminopyrimidine [3H]AE F119209 (4(cis-4-[3H]isopropyl cyclohexylamino)-5-chloro-6-ethyl pyrimidine) using partially purified complex I from Musca domestica exhibited little unspecific binding and allowed reliable determination of dissociation constants. Competition experiments consistently demonstrated that all tested hydrophobic inhibitors of complex I share a common binding domain with partially overlapping sites. Although the rotenone site overlaps with both the piericidin A and the capsaicin site, the latter two sites do not overlap. This is in contrast to the interpretation of enzyme kinetics that have previously been used to define three classes of complex I inhibitors. The existence of only one large inhibitor binding pocket in the hydrophobic part of complex I is discussed in the light of possible mechanisms of proton translocation.
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Affiliation(s)
- J G Okun
- Universitätsklinikum Frankfurt, Institut für Biochemie I, D-60590 Frankfurt am Main, Federal Republic of Germany
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17
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Affiliation(s)
- P J Quinn
- Division of Life Sciences, King's College, London, UK
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18
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Degli Esposti M. Inhibitors of NADH-ubiquinone reductase: an overview. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1364:222-35. [PMID: 9593904 DOI: 10.1016/s0005-2728(98)00029-2] [Citation(s) in RCA: 378] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This article provides an updated overview of the plethora of complex I inhibitors. The inhibitors are presented within the broad categories of natural and commercial compounds and their potency is related to that of rotenone, the classical inhibitor of complex I. Among commercial products, particular attention is dedicated to inhibitors of pharmacological or toxicological relevance. The compounds that inhibit the NADH-ubiquinone reductase activity of complex I are classified according to three fundamental types of action on the basis of available evidence and recent insights: type A are antagonists of the ubiquinone substrate, type B displace the ubisemiquinone intermediate, and type C are antagonists of the ubiquinol product.
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Affiliation(s)
- M Degli Esposti
- Department of Biochemistry and Molecular Biology, Monash University, 3168 Clayton, Victoria, Australia.
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Viola A, Jeunet A, Decreau R, Chanon M, Julliard M. ESR studies of a series of phthalocyanines. Mechanism of phototoxicity. Comparative quantitation of O2-. using ESR spin-trapping and cytochrome c reduction techniques. Free Radic Res 1998; 28:517-32. [PMID: 9702532 DOI: 10.3109/10715769809066889] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ESR experiments with 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP) and the spin-trap 5,5-dimethyl pyrroline-N-oxide (DMPO) have been performed on a series of new phthalocyanines: the bis(tri-n-hexylsiloxy) silicon phthalocyanine ([(nhex)3SiO]2SiPc), the hexadecachloro zinc phthalocyanine (ZnPcCl16), the hexadecachloro aluminum phthalocyanine (AlPcCl16), the hexadecachloro aluminum phthalocyanine sulfate (HSO4AlPcCl16), whose photocytotoxicity has been studied against various leukemic and melanotic cell lines. Type I and Type II pathways occur simultaneously in DMF although the Type II seems to be prevalent. These results are not changed when the bis(tri-n-hexylsiloxy) silicon phthalocyanine is entrapped into liposomes. By contrast, the Type I process is favored in membrane models for all the perchlorinated phthalocyanines. This modified behavior may be accounted on a possible stacking of phthalocyanines in membranes and a preventing effect of axial ligands against aggregation in the case of the bis(tri-n-hexylsiloxy) silicon phthalocyanine. The photodynamic action of zinc perchlorinated phthalocyanine is not dependent on singlet oxygen, phototoxicity of this molecule being essentially mediated by oxygen free radicals. Quantitation of the superoxide radical was accomplished, with good agreement, by two techniques: the cytochrome c reduction and the ESR quantitation based on the double integration of the first derivative of the ESR signal. The disproportionation of the superoxide radical or degradation of the spin-trap seem to be avoided in aprotic solvents such as DMF.
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Affiliation(s)
- A Viola
- Laboratoire AM3-ESA 6009, Faculté des Sciences Saint-Jérôme, Marseille, France
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20
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Hadjur C, Wagnieres G, Monnier P, Bergh H. EPR and Spectrophotometric Studies of Free Radicals (O2°−, °OH, BPD-MA°−) and Singlet Oxygen (1O2) Generated by Irradiation of Benzoporphyrin Derivative Monoacid Ring A. Photochem Photobiol 1997. [DOI: 10.1111/j.1751-1097.1997.tb01929.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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21
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Plastoquinol and α-tocopherol quinol are more active than ubiquinol and α-tocopherol in inhibition of lipid peroxidation. Chem Phys Lipids 1997. [DOI: 10.1016/s0009-3084(97)00027-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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22
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Majander A, Finel M, Savontaus ML, Nikoskelainen E, Wikström M. Catalytic activity of complex I in cell lines that possess replacement mutations in the ND genes in Leber's hereditary optic neuropathy. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 239:201-7. [PMID: 8706709 DOI: 10.1111/j.1432-1033.1996.0201u.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Short-chain ubiquinone analogues act as electron acceptors and as inhibitors in the lymphoblast mitochondria of ND1/3460 mutants, which indicates structural changes in the ubiquinone-binding domain of Complex I in this mutant. The ND4/11778 mutant and two secondary ND5 mutants studied are associated with reductions of at least 50, 35 and 30% in the catalytic rate constant, respectively. However, the efficiency of oxidative phosphorylation is unaffected in all these ND mutants. The rate of respiration is only slightly limited by Complex I in lymphoblast mitochondria. Consequently, there is a 30-35% reduction in the electron flow through Complex I compared with that through Complex II, and an increased lactate/pyruvate ratio, in the ND1 and ND4 mutants, but these factors were unaffected in the secondary ND5 mutants. Energy metabolism is thus less severely affected in the secondary mutants than in the primary mutants, which supports the division into these two categories. An increased ubiquinone-10 content in the mitochondrial membrane of all the mutants, and enhanced succinate dehydrogenase and citrate synthase activities in the ND4 mutant, are proposed to be compensatory changes. The efficiency of these changes and the level of kinetic limitation of respiration by Complex I in each tissue are proposed to determine the clinical development of the disease.
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Affiliation(s)
- A Majander
- Department of Medical Chemistry, University of Helsinki, Finland
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23
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Skowronek M, Jemioła-Rzemińska M, Kruk J, Strzałka K. Influence of the redox state of ubiquinones and plastoquinones on the order of lipid bilayers studied by fluorescence anisotropy of diphenylhexatriene and trimethylammonium diphenylhexatriene. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1280:115-9. [PMID: 8634304 DOI: 10.1016/0005-2736(95)00264-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The measurements of diphenylhexatriene (DPH) and trimethylammonium diphenylhexatriene (TMA-DPH) fluorescence anisotropy in egg yolk lecithin (EYL) and of DPH anisotropy in dipalmitoylphosphatidylcholine (DPPC) liposomes containing different concentrations of oxidized and reduced ubiquinone (UQ) and plastoquinone (PQ) homologues have been performed. All the oxidized UQ homologues strongly induced ordering of EYL membrane structure, whereas in DPPC liposomes, above the phase transition temperature, the most pronounced effect showed UQ-4. PQ-2 and PQ-9 were less effective than the corresponding ubiquinones in this respect. The reduced forms of UQ and PQ homologues increased the order of membrane lipids to a smaller extent than the corresponding quinones both in the interior of the membrane and closer to its surface. Nevertheless, the investigated prenylquinols showed stronger increase in the membrane order than alpha-tocopherol or alpha-tocopherol acetate, which could be connected with binding of prenylquinol head groups to phospholipid molecules by hydrogen bonds. The strong ordering influence of ubiquinones on the membrane structure was attributed to methoxyl groups of the UQ quinone rings.
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Affiliation(s)
- M Skowronek
- Department of Plant Physiology and Biochemistry, The Jan Zurzycki Institute of Molecular Biology, Jagiellonian Univeristy, Kraków, Poland
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24
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Jemiola-Rzeminska M, Kruk J, Skowronek M, Strzalka K. Location of ubiquinone homologues in liposome membranes studied by fluorescence anisotropy of diphenyl-hexatriene and trimethylammonium-diphenyl-hexatriene. Chem Phys Lipids 1996; 79:55-63. [PMID: 8907243 DOI: 10.1016/0009-3084(95)02507-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The measurements of diphenyl-hexatriene (DPH) and trimethylammonium-diphenyl-hexatriene (TMA-DPH) fluorescence anisotropy in dipalmitoylphosphatidylcholine (DPPC) and egg yolk lecithin (EYL) liposomes containing different concentrations of various ubiquinone (UQ) homologues have been performed. UQ-4 induced the highest DPH anisotropy increase in DPPC liposomes, whereas for higher UQ homologues the anisotropy was lowered with the increase of UQ side-chain length. These differences were less pronounced in EYL liposomes. It was concluded that at a higher content in the membranes (3-4 mol%), the short-chain ubiquinones are arranged parallel to lipid fatty acid chains, whereas long-chain homologues are progressively removed from the lipid acyl chains into the midplane region of the membrane. At the lower (1-2 mol%) concentrations, long-chain quinones seem to be evenly distributed within the membrane, especially in EYL membranes. UQ-10 in EYL liposomes perturbed TMA-DPH to a similar extend as the short-chain ubiquinones indicating that UQ-10 penetrates the interface regions of the membrane where its redox reactions occur. The localization and physical state of UQ-10 in native membranes is discussed.
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Affiliation(s)
- M Jemiola-Rzeminska
- Department of Physiology and Biochemistry of Plants, The Jan Zurzycki Institute of Molecular Biology, Jagiellonian University, Krakow, Poland
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25
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Degli Esposti M, Ngo A, McMullen GL, Ghelli A, Sparla F, Benelli B, Ratta M, Linnane AW. The specificity of mitochondrial complex I for ubiquinones. Biochem J 1996; 313 ( Pt 1):327-34. [PMID: 8546703 PMCID: PMC1216902 DOI: 10.1042/bj3130327] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We report the first detailed study on the ubiquinone (coenzyme Q; abbreviated to Q) analogue specificity of mitochondrial complex I, NADH:Q reductase, in intact submitochondrial particles. The enzymic function of complex I has been investigated using a series of analogues of Q as electron acceptor substrates for both electron transport activity and the associated generation of membrane potential. Q analogues with a saturated substituent of one to three carbons at position 6 of the 2,3-dimethoxy-5-methyl-1,4-benzoquinone ring have the fastest rates of electron transport activity, and analogues with a substituent of seven to nine carbon atoms have the highest values of association constant derived from NADH:Q reductase activity. The rate of NADH:Q reductase activity is potently but incompletely inhibited by rotenone, and the residual rotenone-insensitive rate is stimulated by Q analogues in different ways depending on the hydrophobicity of their substituent. Membrane potential measurements have been undertaken to evaluate the energetic efficiency of complex I with various Q analogues. Only hydrophobic analogues such as nonyl-Q or undecyl-Q show an efficiency of membrane potential generation equivalent to that of endogenous Q. The less hydrophobic analogues as well as the isoprenoid analogue Q-2 are more efficient as substrates for the redox activity of complex I than for membrane potential generation. Thus the hydrophilic Q analogues act also as electron sinks and interact incompletely with the physiological Q site in complex I that pumps protons and generates membrane potential.
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Affiliation(s)
- M Degli Esposti
- Centre for Molecular Biology and Medicine, Monash University, Clayton, Victoria, Australia
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26
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Degli Esposti M, Carelli V, Ghelli A, Ratta M, Crimi M, Sangiorgi S, Montagna P, Lenaz G, Lugaresi E, Cortelli P. Functional alterations of the mitochondrially encoded ND4 subunit associated with Leber's hereditary optic neuropathy. FEBS Lett 1994; 352:375-9. [PMID: 7926004 DOI: 10.1016/0014-5793(94)00971-6] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease associated with point mutations in mitochondrial DNA. The most frequent of these mutations is the G-to-A substitution at nucleotide position 11,778 which changes an evolutionarily conserved arginine with a histidine at position 340 in subunit ND4 of NADH:ubiquinone reductase (respiratory complex I). We report that this amino acid substitution alters the affinity of complex I for the ubiquinone substrate and induces resistance towards its potent inhibitor rotenone in mitochondria of LHON patients. Such changes could reflect a substantial loss in the energy conserving function of NADH:ubiquinone reductase and thus explain the pathological effect of the ND4/11,778 mutation.
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Affiliation(s)
- M Degli Esposti
- Department of Biology, Institute of Clinical Neurology, University of Bologna, Italy
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27
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Degli Esposti M, Ghelli A, Ratta M, Cortes D, Estornell E. Natural substances (acetogenins) from the family Annonaceae are powerful inhibitors of mitochondrial NADH dehydrogenase (Complex I). Biochem J 1994; 301 ( Pt 1):161-7. [PMID: 8037664 PMCID: PMC1137156 DOI: 10.1042/bj3010161] [Citation(s) in RCA: 176] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Natural products from the plants of the family Annonaceae, collectively called Annonaceous acetogenins, are very potent inhibitors of the NADH-ubiquinone reductase (Complex I) activity of mammalian mitochondria. The properties of five of such acetogenins are compared with those of rotenone and piericidin, classical potent inhibitors of Complex I. Rolliniastatin-1 and rolliniastatin-2 are more powerful than piericidin in terms of both their inhibitory constant and the protein-dependence of their titre in bovine submitochondrial particles. These acetogenins could be considered therefore the most potent inhibitors of mammalian Complex I. Squamocin and otivarin also have an inhibitory constant lower than that of piericidin, but display a larger protein-dependence of the titre. Squamocin and otivarin, contrary to the other acetogenins, behave qualitatively like rotenone. Rolliniastatin-2 shows unique properties as its interaction, although mutually exclusive to that of piericidin, appears to be mutually non-exclusive to that of rotenone. It is the first time that a potent inhibitor of Complex I is found not to overlap the active site of rotenone.
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28
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Mathai J, Sauna Z, John O, Sitaramam V. Rate-limiting step in electron transport. Osmotically sensitive diffusion of quinones through voids in the bilayer. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)82277-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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29
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Kruk J, Strzałka K, Leblanc RM. Fluorescence properties of plastoquinol, ubiquinol and alpha-tocopherol quinol in solution and liposome membranes. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 1993; 19:33-8. [PMID: 8336241 DOI: 10.1016/1011-1344(93)80090-v] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
It was found that plastoquinol-9, ubiquinol-10 and alpha-tocopherol quinol show intrinsic fluorescence in organic solvents and in liposomes. Their fluorescence spectra in solution showed the presence of one emission band with maximum intensity in the range 319.0-327.0 nm for plastoquinol and 321.5-326.5 nm for alpha-tocopherol quinol, which is the longest wavelength shifted in polar solvents. The emission band at about 371 nm for ubiquinol was not sensitive to solvent polarity. For all three prenylquinones the fluorescence quantum efficiency changed significantly in solvents of different polarities, being the highest in ethanol and the lowest in hexane in the case of plastoquinol and alpha-tocopherol quinol, whereas ubiquinol fluorescence showed the opposite effect. These spectral parameters were applied to determination of prenylquinol localization in liposome membranes.
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Affiliation(s)
- J Kruk
- Department of Physiology and Biochemistry of Plants, Jan Zurzycki Institute of Molecular Biology, Jagiellonian University, Kraków, Poland
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30
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Oleskin AV, Samullov VD. pH-Abhängigkeit der Cytochromc2 (c)-Reduktion und des Membranpotentials (Δ Ψ) in Modellsystemen und Chromatophoren von Purpurbakterien. J Basic Microbiol 1992. [DOI: 10.1002/jobm.3620320608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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31
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Bironaite DA, Cenas NK, Kulys JJ. The rotenone-insensitive reduction of quinones and nitrocompounds by mitochondrial NADH:ubiquinone reductase. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1060:203-9. [PMID: 1932041 DOI: 10.1016/s0005-2728(09)91008-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The rotenone-insensitive reduction of quinones and aromatic nitrocompounds by mitochondrial NADH: ubiquinone reductase (complex I, EC 1.6.99.3) has been studied. It was found that these reactions proceed via a mixed one- and two-electron transfer. The logarithms of the bimolecular rate constants of oxidation (TN/Km) are proportional to the one-electron-reduction potentials of oxidizers. The reactivities of nitrocompounds are close to those of quinones. Unlike the reduction of ferricyanide, these reactions are not inhibited by NADH. However, they are inhibited by NAD+ and ADP-ribose, which also act as the mixed-type inhibitors for ferricyanide. TN/Km of quinones and nitrocompounds depend on the NAD+/NADH ratio, but not on NAD+ concentration. They are diminished by the limiting factors of 2.5-3.5 at NAD+/NADH greater than 200. It seems that rotenone-insensitive reduction of quinones and nitrocompounds takes place near the NAD+/NADH and ferricyanide binding site, and the inhibition is caused by induced conformational changes after the binding of NAD+ or ADP-ribose.
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Affiliation(s)
- D A Bironaite
- Institute of Biochemistry, Lithuanian Academy of Sciences, Vilnius
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32
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Cénas NK, Bironaité DA, Kulys JJ. On the mechanism of rotenone-insensitive reduction of quinones by mitochondrial NADH:ubiquinone reductase. The high affinity binding of NAD+ and NADH to the reduced enzyme form. FEBS Lett 1991; 284:192-4. [PMID: 1905649 DOI: 10.1016/0014-5793(91)80682-s] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
NADH acts as an incomplete competitive inhibitor for 5,8-dioxy-1,4-naphtoquinone during its rotenone-insensitive reduction by mitochondrial NADH:ubiquinone reductase. NAD+ and ADP-ribose act as incomplete mixed-type inhibitors. Ki of NAD+ and NADH towards quinone are about one order less than towards ferricyanide. The bimolecular rate constant of the reduction of the enzyme by NADH in the quinone reductase reaction is about 2 times less than that of ferricyanide reductase reaction. These data indicate that the reduction site of 5,8-dioxy-1,4-naphtoquinone is close to NAD+/NADH and ferricyanide binding site. It seems that during the steady-state reduction of ferricyanide and 5,8-dioxy-1,4-naphtoquinone these oxidizers react with NADH:ubiquinone reductase reduced to different extents.
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Affiliation(s)
- N K Cénas
- Institute of Biochemistry, Lithuanian Academy of Sciences, Vilnius, USSR
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33
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Hafner RP, Brown GC, Brand MD. Analysis of the control of respiration rate, phosphorylation rate, proton leak rate and protonmotive force in isolated mitochondria using the 'top-down' approach of metabolic control theory. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 188:313-9. [PMID: 2156698 DOI: 10.1111/j.1432-1033.1990.tb15405.x] [Citation(s) in RCA: 229] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The rate of respiration of isolated mitochondria was set at different values by addition of either oligomycin or an ADP-regenerating system (glucose and different amounts of hexokinase). We measured the relationship between respiration rate and membrane potential as respiration was titrated by the addition of malonate under each condition. We used the flux control summation and connectivity theorems and the branching theorem of metabolic control theory to calculate the control over respiration rate exerted by the respiratory chain (and associated reactions), phosphorylating system (and associated reactions) and proton leak at each respiration rate. The analysis also yielded the flux control coefficients of these three reactions over phosphorylation rate and proton leak rate and their concentration control coefficients over protonmotive force. We found that respiration rate was controlled largely by the proton leak under non-phosphorylating conditions, by the phosphorylating system at intermediate rates and by both the phosphorylating system and the respiratory chain in state 3. The rate of phosphorylation was controlled largely by the phosphorylating system itself in state 4 and at intermediate rates, while state 3 control was shared between the phosphorylating system and the respiratory chain; the proton leak had insignificant control. In all states the phosphorylating system had large negative control over the proton leak; the chain and the proton leak both had large positive control coefficients. The protonmotive force was controlled by the chain and by the phosphorylating system; the proton leak had little control.
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Affiliation(s)
- R P Hafner
- Department of Biochemistry, University of Cambridge, England
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34
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Kagan VE, Serbinova EA, Koynova GM, Kitanova SA, Tyurin VA, Stoytchev TS, Quinn PJ, Packer L. Antioxidant action of ubiquinol homologues with different isoprenoid chain length in biomembranes. Free Radic Biol Med 1990; 9:117-26. [PMID: 2227528 DOI: 10.1016/0891-5849(90)90114-x] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Ubiquinones (CoQn) are intrinsic lipid components of many membranes. Besides their role in electron-transfer reactions they may act as free radical scavengers, yet their antioxidant function has received relatively little study. The efficiency of ubiquinols of varying isoprenoid chain length (from Q0 to Q10) in preventing (Fe2+ + ascorbate)-dependent or (Fe2+ + NADPH)-dependent lipid peroxidation was investigated in rat liver microsomes and brain synaptosomes and mitochondria. Ubiquinols, the reduced forms of CoQn, possess much greater antioxidant activity than the oxidized ubiquinone forms. In homogenous solution the radical scavenging activity of ubiquinol homologues does not depend on the length of their isoprenoid chain. However in membranes ubiquinols with short isoprenoid chains (Q1-Q4) are much more potent inhibitors of lipid peroxidation than the longer chain homologues (Q5-Q10). It is found that: i) the inhibitory action, that is, antioxidant efficiency of short-chain ubiquinols decreases in order Q1 greater than Q2 greater than Q3 greater than Q4; ii) the antioxidant efficiency of long-chain ubiquinols is only slightly dependent on their concentrations in the order Q5 greater than Q6 greater than Q7 greater than Q8 greater than Q9 greater than Q10 and iii) the antioxidant efficiency of Q0 is markedly less than that of other homologues. Interaction of ubiquinols with oxygen radicals was followed by their effects on luminol-activated chemiluminescence. Ubiquinols Q1-Q4 at 0.1 mM completely inhibit the luminol-activated NADPH-dependent chemiluminescent response of microsomes, while homologues Q6-Q10 exert no effect. In contrast to ubiquinol Q10 (ubiquinone Q10) ubiquinone Q1 synergistically enhances NADPH-dependent regeneration of endogenous vitamin E in microsomes thus providing for higher antioxidant protection against lipid peroxidation. The differences in the antioxidant potency of ubiquinols in membranes are suggested to result from differences in partitioning into membranes, intramembrane mobility and non-uniform distribution of ubiquinols resulting in differing efficiency of interaction with oxygen and lipid radicals as well as different efficiency of ubiquinols in regeneration of endogenous vitamin E.
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Affiliation(s)
- V E Kagan
- Institute of Physiology, Bulgarian Academy of Sciences, Sofia
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35
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Dry IB, Moore AL, Day DA, Wiskich JT. Regulation of alternative pathway activity in plant mitochondria: nonlinear relationship between electron flux and the redox poise of the quinone pool. Arch Biochem Biophys 1989; 273:148-57. [PMID: 2757390 DOI: 10.1016/0003-9861(89)90173-2] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The dependence of respiratory flux via the alternative pathway on the redox poise of the ubiquinone (Q) pool was investigated in soybean cotyledon mitochondria. A marked nonlinear relationship was observed between Q-pool reduction level and O2 uptake via the alternative oxidase. Significant engagement of the alternative pathway was not apparent until Q-pool reduction level reached 35-40% but increased disproportionately on further reduction. Similar results were obtained with electron donation from either Complex 1 or Complex 2. Close agreement was obtained over a range of experimental conditions between the estimated contribution of the alternative pathway to total respiratory flux, as measured with salicylhydroxamic acid, and that predicted from the redox poise of the Q-pool. These results are discussed in terms of existing models of the regulation of respiratory flux via the alternative pathway.
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Affiliation(s)
- I B Dry
- Department of Botany, University of Adelaide, South Australia
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36
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Chazotte B, Hackenbrock CR. Lateral Diffusion as a Rate-limiting Step in Ubiquinone-mediated Mitochondrial Electron Transport. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83687-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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37
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Okamoto T, Fukunaga Y, Ida Y, Kishi T. Determination of reduced and total ubiquinones in biological materials by liquid chromatography with electrochemical detection. JOURNAL OF CHROMATOGRAPHY 1988; 430:11-9. [PMID: 3215946 DOI: 10.1016/s0378-4347(00)83129-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A convenient and reliable liquid chromatographic (LC) method with electrochemical detection (ED) was developed for the determination of reduced (ubiquinol) and total ubiquinones in biological materials. After extraction of samples with n-hexane, ubiquinol was separated on a reversed-phase column and assayed directly by ED. In order to determine the total amount of a ubiquinone in biological samples, the unbiquinone was converted into the corresponding reduced form by treatment with sodium borohydride. No significant interfering peak (plastoquinol-9, ubichromenol-9, etc.) was observed in the elution areas of ubiquinol-7 to -11. This LC-ED method was about 70 times more sensitive than the previous LC-UV method and was able to detect 150 pg of ubiquinol-10. The method was applied satisfactorily to the determination of the contents of ubiquinol homologues in biological materials. The content of ubiquinols is a major component of the total ubiquinones in human plasma and urine and rat plasma and liver, but a minor component in rat heart and kidney.
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Affiliation(s)
- T Okamoto
- Faculty of Pharmaceutical Sciences, Kobe-Gakuin University, Japan
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38
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Reed JS, Ragan CI. The effect of rate limitation by cytochrome c on the redox state of the ubiquinone pool in reconstituted NADH: cytochrome c reductase. Biochem J 1987; 247:657-62. [PMID: 2827635 PMCID: PMC1148462 DOI: 10.1042/bj2470657] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The kinetic model of Ragan & Cottingham [(1985) Biochim. Biophys. Acta 811, 13-31] for electron transport through a mobile pool of quinone predicts that, under certain conditions, the normal linear dependence of electron flow on the degree of reduction (or oxidation) of the quinone should no longer be found. These conditions can be met by reconstituted NADH: cytochrome c reductase (Complex I-III from bovine heart) when electron flow is rate-limited by a low concentration of cytochrome c. We show that, in such a system, the dependence of activity (varied by inhibition with rotenone) on the steady-state level of quinone reduction is indeed non-linear and very closely accounted for by the theory.
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Affiliation(s)
- J S Reed
- Department of Biochemistry, University of Southampton, U.K
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Brand MD, Murphy MP. Control of electron flux through the respiratory chain in mitochondria and cells. Biol Rev Camb Philos Soc 1987; 62:141-93. [PMID: 3300795 DOI: 10.1111/j.1469-185x.1987.tb01265.x] [Citation(s) in RCA: 160] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Kucera I, Kozák L, Dadák V. Is the ubiquinone pool in the respiratory chain of the bacterium Paracoccus denitrificans really unhomogeneous? Arch Biochem Biophys 1987; 253:199-204. [PMID: 3813563 DOI: 10.1016/0003-9861(87)90652-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We have established the participation of a mobile redox pool in the respiratory chain of anaerobically grown bacterium Paracoccus denitrificans. In testing the kinetical homogeneity of the pool it was found that the ratio of fluxes of electron transport toward the terminal acceptors oxygen and nitrate was coincident for the respiratory substrates NADH and succinate; this provides evidence against the preferential link of one dehydrogenase with a distinct terminal enzyme through the separate pool of ubiquinone. The deviation from the expected behavior observed in comparing the titration of NADH oxidase and succinate oxidase with respiratory inhibitors such as mucidin (inhibitor in the bc1 region) or cyanide can be accounted for by the activation of succinate dehydrogenase upon the increase in the reduced state of respiratory components during the titration.
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Hackenbrock CR, Chazotte B, Gupte SS. The random collision model and a critical assessment of diffusion and collision in mitochondrial electron transport. J Bioenerg Biomembr 1986; 18:331-68. [PMID: 3021714 DOI: 10.1007/bf00743010] [Citation(s) in RCA: 307] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This review focuses on our studies over the past ten years which reveal that the mitochondrial inner membrane is a fluid-state rather than a solid-state membrane and that all membrane proteins and redox components which catalyze electron transport and ATP synthesis are in constant and independent diffusional motion. The studies reviewed represent the experimental basis for the random collision model of electron transport. We present five fundamental postulates upon which the random collision model of mitochondrial electron transport is founded: All redox components are independent lateral diffusants; Cytochrome c diffuses primarily in three dimensions; Electron transport is a diffusion-coupled kinetic process; Electron transport is a multicollisional, obstructed, long-range diffusional process; The rates of diffusion of the redox components have a direct influence on the overall kinetic process of electron transport and can be rate limiting, as in diffusion control. The experimental rationales and the results obtained in testing each of the five postulates of the random collision model are presented. In addition, we offer the basic concepts, criteria and experimental strategies that we believe are essential in considering the significance of the relationship between diffusion and electron transport. Finally, we critically explore and assess other contemporary studies on the diffusion of inner membrane components related to electron transport including studies on: rotational diffusion, immobile fractions, complex formation, dynamic aggregates, and rates of diffusion. Review of all available data confirms the random collision model and no data appear to exist that contravene it. It is concluded that mitochondrial electron transport is a diffusion-based random collision process and that diffusion has an integral and controlling affect on electron transport.
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Abstract
Strong evidence for a random collisional mechanism for ubiquinone-mediated electron transfer is provided by the characteristic kinetic properties of respiratory chains originally explored by Kröger, A., and Klingenberg, M. (1973), Eur. J. Biochem. 34, 313-323. A kinetic model which leads to this so-called "simple Q-pool behavior" has been described and we use this in reviewing evidence that electron transfer is diffusion-controlled as well as diffusion-coupled. We also consider mechanisms by which the kinetics of electron transfer might deviate from simple Q-pool behavior and how these might be implicated in the regulation of electron transport.
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Linke P, Bechmann G, Gothe A, Weiss H. Dimeric ubiquinol:cytochrome c reductase of Neurospora mitochondria contains one cooperative ubiquinone-reduction centre. EUROPEAN JOURNAL OF BIOCHEMISTRY 1986; 158:615-21. [PMID: 3015618 DOI: 10.1111/j.1432-1033.1986.tb09799.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
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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Choudhry ZM, Kotlyar AB, Vinogradov AD. Studies on the succinate dehydrogenating system. Interaction of the mitochondrial succinate-ubiquinone reductase with pyridoxal phosphate. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 850:131-8. [PMID: 3707947 DOI: 10.1016/0005-2728(86)90017-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
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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von Jagow G, Link TA, Ohnishi T. Organization and function of cytochrome b and ubiquinone in the cristae membrane of beef heart mitochondria. J Bioenerg Biomembr 1986; 18:157-79. [PMID: 2426249 DOI: 10.1007/bf00743462] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The arrangement and function of the redox centers of the mammalian bc1 complex is described on the basis of structural data derived from amino acid sequence studies and secondary structure predictions and on the basis of functional studies (i.e., EPR data, inhibitor studies, and kinetic experiments). Two ubiquinone reaction centers do exist--a QH2 oxidation center situated at the outer, cytosolic surface of the cristae membrane (Q0 center), and a Q reduction center (Qi center) situated more to the inner surface of the cristae membrane. The Q0 center is formed by the b-566 domain of cytochrome b, the FeS protein, and maybe an additional small subunit, whereas the Qi center is formed by the b-562 domain of cytochrome b and presumably the 13.4 kDa protein ("QP-C"). The "Q binding proteins" are proposed to be protein subunits of the Q reaction centers of various multiprotein complexes. The path of electron flow branches at the Q0 center, half of the electrons flowing via the high-potential cytochrome chain to oxygen and half of the electrons cycling back into the Q pool via the cytochrome b path connecting the two Q reaction centers. During oxidation of QH2, 2H+ are released to the cytosolic space and during reduction of Q, 2H+ are taken up from the matrix side, resulting in a net transport across the membrane of 2H+ per e- flown from QH2 to cytochrome c, the H+ being transported across the membrane as H (H+ + e-) by the mobile carrier Q. The authors correct their earlier view of cytochrome b functioning as a H+ pump, proposing that the redox-linked pK changes of the acidic groups of cytochrome b are involved in the protonation/deprotonation processes taking place during the reduction and oxidation of Q. The reviewers stress that cytochrome b is in equilibrium with the Q pool via the Qi center, but not via the Q0 center. Their view of the mechanisms taking place at the reductase is a Q cycle linked to a Q-pool where cytochrome b is acting as an electron pump.
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Tushurashvili PR, Gavrikova EV, Ledenev AN, Vinogradov AD. Studies on the succinate dehydrogenating system. Isolation and properties of the mitochondrial succinate-ubiquinone reductase. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 809:145-59. [PMID: 2994719 DOI: 10.1016/0005-2728(85)90057-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A simple procedure for preparation of highly purified soluble succinate-ubiquinone reductase from bovine heart mitochondrial particles is described. The enzyme exhibits four major bands on sodium dodecyl sulfate gel electrophoresis and contains (nmol per mg protein): covalently bound flavin, 6; non-heme iron, 53; acid-labile sulfur, 50; cytochrome b-560 heme, 1.2. The enzyme catalyzes thenoyltrifluoroacetone, or carboxin-sensitive (pure non-competitive with Q2) reduction of Q2 by succinate with a turnover number close to that in parent submitochondrial particles. The succinate reduced enzyme exhibits ferredoxin-type iron-sulfur center EPR-signal (g = 1.94 species) and a semiquinone signal (g = 2.00). An oxidized preparation shows a symmetric signal centered around g = 2.01. An unusual dissociation of the enzyme in the absence of a detergent is described. When added to the assay mixture from a concentrated protein-detergent solution, the enzyme does not reduce Q2 being highly reactive towards ferricyanide ('low Km ferricyanide reactive site'; Vinogradov, A.D., Gavrikova, E.V. and Goloveshkina, V.G. (1975) Biochem. Biophys. Res. Commun. 65, 1264-1269). The ubiquinone reductase, not the ferricyanide reductase was observed when the enzyme was added to the assay mixture from the diluted protein-detergent solutions. Thus the dissociation of succinate dehydrogenase from the complex occurs in the absence of a detergent dependent on the concentration of the protein-detergent complex in the stock preparation where the samples for the assay are taken from. An active antimycin-sensitive succinate-cytochrome c reductase was reconstituted by admixing of the soluble succinate-ubiquinone reductase and the cytochrome b-c1 complex, i.e., from the complexes which both contain the ubiquinone reactivity conferring protein (QPs). Cytochrome c reductase was also reconstituted from the succinate-ubiquinone reductase and succinate-cytochrome c reductase containing inactivated succinate dehydrogenase. The reconstitution experiments suggest that there exists a specific protein-protein (or lipid) interaction between QPs and a certain component(s) of the b-c1 complex.
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Jørgensen BM, Rasmussen HN, Rasmussen UF. Ubiquinone reduction pattern in pigeon heart mitochondria. Identification of three distinct ubiquinone pools. Biochem J 1985; 229:621-9. [PMID: 4052014 PMCID: PMC1145104 DOI: 10.1042/bj2290621] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Intact pigeon heart mitochondria showed 10-30% ubiquinone reduction in the absence of substrates. This reduction could not be ascribed to endogenous substrates, as judged by lack of effect of inhibitors and uncouplers and by the very low endogenous respiratory rate. Addition of NADH in the presence of antimycin caused further reduction of about 10% ubiquinone, apparently coupled to the rotenone- and antimycin-sensitive exo-NADH oxidase system [Rasmussen (1969) FEBS Lett. 2, 157-162]. Citric acid cycle substrates reduced most of the remaining ubiquinone in the presence of antimycin; 15-20% of the total ubiquinone content was still in the oxidized form under the most reducing conditions. Three pools of ubiquinone therefore appeared to be present in heart mitochondria: a metabolically inactive pool consisting of reduced as well as oxidized ubiquinone, a pool coupled to oxidation of added (cytoplasmic) NADH, and the well-known pool coupled to citric acid cycle oxidations. Ferricyanide selectively oxidized the ubiquinol reduced by added NADH, indicating that this pool is situated on the outer surface of the mitochondrial inner membrane. Ubiquinone reduction levels were determined with a new method, which is described in detail.
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Okamoto T, Fukui K, Nakamoto M, Kishi T, Okishio T, Yamagami T, Kanamori N, Kishi H, Hiraoka E. High-performance liquid chromatography of coenzyme Q-related compounds and its application to biological materials. JOURNAL OF CHROMATOGRAPHY 1985; 342:35-46. [PMID: 4044758 DOI: 10.1016/s0378-4347(00)84487-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A convenient and precise method for the separation and determination of coenzyme Q (CoQ)-related compounds (CoQ homologues, plastoquinone-9, ubichromenol-9, etc.) was developed using high-performance liquid chromatography (HPLC). All compounds tested were separated using a reverse-phase column with a suitable mobile phase and detected at a wavelength of 275 nm. CoQ extracts in plasma and erythrocytes were purified by thin-layer chromatography prior to HPLC analysis, but such purification was not necessary when determining CoQ in urine and tissues. Hydroquinone forms of CoQ existing in animal tissues were oxidized to the corresponding quinone forms with potassium hexacyanoferrate(III). This HPLC method was applied satisfactorily to the determination of the contents of CoQ homologues in human and animal samples. CoQ10 was the only homologue detected in human samples, and CoQ8, CoQ9 and CoQ10 were native homologues of CoQ in rat tissues. Ubichromenol-9 and plastoquinone-9 were not detected in these samples.
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Ragan CI, Cottingham IR. The kinetics of quinone pools in electron transport. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 811:13-31. [PMID: 3986195 DOI: 10.1016/0304-4173(85)90003-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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