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Mounkoro P, Michel T, Golinelli-Cohen MP, Blandin S, Davioud-Charvet E, Meunier B. A role for the succinate dehydrogenase in the mode of action of the redox-active antimalarial drug, plasmodione. Free Radic Biol Med 2021; 162:533-541. [PMID: 33232753 DOI: 10.1016/j.freeradbiomed.2020.11.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 11/02/2020] [Accepted: 11/10/2020] [Indexed: 11/26/2022]
Abstract
Malaria, caused by protozoan parasites, is a major public health issue in subtropical countries. An arsenal of antimalarial treatments is available, however, resistance is spreading, calling for the development of new antimalarial compounds. The new lead antimalarial drug plasmodione is a redox-active compound that impairs the redox balance of parasites leading to cell death. Based on extensive in vitro assays, a model of its mode of action was drawn, involving the generation of active plasmodione metabolites that act as subversive substrates of flavoproteins, initiating a redox cycling process producing reactive oxygen species. We showed that, in yeast, the mitochondrial respiratory chain NADH-dehydrogenases are the main redox-cycling target enzymes. Furthermore, our data supported the proposal that plasmodione is a pro-drug acting via its benzhydrol and benzoyl metabolites. Here, we selected plasmodione-resistant yeast mutants to further decipher plasmodione mode of action. Of the eleven mutants analysed, nine harboured a mutation in the FAD binding subunit of succinate dehydrogenase (SDH). The analysis of the SDH mutations points towards a specific role for SDH-bound FAD in plasmodione bioactivation, possibly in the first step of the process, highlighting a novel property of SDH.
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Affiliation(s)
- Pierre Mounkoro
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, cedex, France
| | - Thomas Michel
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, cedex, France
| | - Marie-Pierre Golinelli-Cohen
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles (ICSN), 91198, Gif-sur-Yvette, cedex, France
| | - Stéphanie Blandin
- Université de Strasbourg, CNRS, Inserm, UPR9022/U1257, Mosquito Immune Responses (MIR), F-67000, Strasbourg, France
| | - Elisabeth Davioud-Charvet
- Université de Strasbourg, Université de Haute-Alsace, Centre National de la Recherche Scientifique (CNRS), UMR 7042 LIMA, Team Bioorganic and Medicinal Chemistry, ECPM, 25 Rue Becquerel, 67087, Strasbourg, France
| | - Brigitte Meunier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, cedex, France.
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Hadni H, Elhallaoui M. 3D-QSAR, docking and ADMET properties of aurone analogues as antimalarial agents. Heliyon 2020; 6:e03580. [PMID: 32322700 PMCID: PMC7168746 DOI: 10.1016/j.heliyon.2020.e03580] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 02/27/2020] [Accepted: 03/09/2020] [Indexed: 01/26/2023] Open
Abstract
The development of multi-resistant strains of plasmodium parasite has become a global problem, therefore, the discovery of new antimalarial agents is the only available solution. In order to improve and propose new compounds with antimalarial activity, the three-dimensional quantitative structure-activity relationship (3D-QSAR) and molecular docking studies were carried on aurone analogues acting as Qo site inhibitors in cytochrome b. The 3D-QSAR model was established in this study based on the Comparative Molecular Field Analysis (CoMFA) and the Comparative Molecular Similarity Indices Analysis (CoMSIA). The good predictability was obtained using the CoMFA model (Q2 = 0.5; R2 = 0.97;R pred 2 = 0.72) and the best CoMSIA model (Q2 = 0.526; R2 = 0.915;R pred 2 = 0.765). The predictive capacity of the developed model was evaluated through external validation using a test set compound and an applicability domain technique. In this study, the Steric, electrostatic and hydrogen bond acceptor fields played a key role in antimalarial activity. The results of the molecular docking revealed theoretically the importance of the residues his183 and his82 in the active site of the heme bL, this result was validated by a new assessment method. Based on the previous results, we designed several new potent Cytochrome b inhibitors and their inhibitory activities were predicted by the best model. Furthermore, these new inhibitors were analyzed for their ADMET properties and drug likeness. These results would be of great help in leading optimization for new drug discovery that can solve the problem of multiple drug resistance.
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Affiliation(s)
- Hanine Hadni
- Engineering Materials, Modeling and Environmental Laboratory, Faculty of Sciences Dhar El mahraz, Sidi Mohammed Ben Abdellah University, B.P. 1796, Atlas, Fes, Morocco
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Hadni H, Elhallaoui M. 2D and 3D-QSAR, molecular docking and ADMET properties in silico studies of azaaurones as antimalarial agents. NEW J CHEM 2020. [DOI: 10.1039/c9nj05767f] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Malaria persists as the most infectious vector-borne disease in the world.
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Affiliation(s)
- Hanine Hadni
- Engineering Materials
- Modeling and Environmental Laboratory
- Faculty of Sciences Dhar El mahraz
- Sidi Mohammed Ben Abdellah University
- Atlas
| | - Menana Elhallaoui
- Engineering Materials
- Modeling and Environmental Laboratory
- Faculty of Sciences Dhar El mahraz
- Sidi Mohammed Ben Abdellah University
- Atlas
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Song Z, Clain J, Iorga BI, Vallières C, Lalève A, Fisher N, Meunier B. Interplay between the hinge region of iron sulphur protein and the Qo site in the bc1 complex - Analysis of Plasmodium-like mutations in the yeast enzyme. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:1487-94. [PMID: 26301481 DOI: 10.1016/j.bbabio.2015.08.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 07/21/2015] [Accepted: 08/19/2015] [Indexed: 10/23/2022]
Abstract
The respiratory chain bc1 complex is central to mitochondrial bioenergetics and the target of antiprotozoals. We characterized a modified yeast bc1 complex that more closely resemble Plasmodium falciparum enzyme. The mutant version was generated by replacing ten cytochrome b Qo site residues by P. falciparum equivalents. The Plasmodium-like changes caused a major dysfunction of the catalytic mechanism of the bc1 complex resulting in superoxide overproduction and respiratory growth defect. The defect was corrected by substitution of the conserved residue Y279 by a phenylalanine, or by mutations in or in the vicinity of the hinge domain of the iron-sulphur protein. It thus appears that side-reactions can be prevented by the substitution Y279F or the modification of the iron-sulphur protein hinge region. Interestingly, P. falciparum - and all the apicomplexan - contains an unusual hinge region. We replaced the yeast hinge region by the Plasmodium version and combined it with the Plasmodium-like version of the Qo site. This combination restored the respiratory growth competence. It could be suggested that, in the apicomplexan, the hinge region and the cytochrome b Qo site have co-evolved to maintain catalytic efficiency of the bc1 complex Qo site.
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Affiliation(s)
- Zehua Song
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, 91198 Gif-sur-Yvette, France
| | - Jérôme Clain
- UMR 216, Faculté de Pharmacie de Paris, Université Paris Descartes, and Institut de Recherche pour le Développement, 75006 Paris, France
| | - Bogdan I Iorga
- Institut de Chimie des Substances Naturelles, CNRS, UPR 2301, Labex LERMIT, 91198 Gif-sur-Yvette, France
| | - Cindy Vallières
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, 91198 Gif-sur-Yvette, France
| | - Anaïs Lalève
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, 91198 Gif-sur-Yvette, France
| | - Nicholas Fisher
- Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA..
| | - Brigitte Meunier
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, 91198 Gif-sur-Yvette, France.
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Saccharomyces cerevisiae-based mutational analysis of the bc1 complex Qo site residue 279 to study the trade-off between atovaquone resistance and function. Antimicrob Agents Chemother 2015; 59:4053-8. [PMID: 25918152 DOI: 10.1128/aac.00710-15] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 04/19/2015] [Indexed: 11/20/2022] Open
Abstract
The bc1 complex is central to mitochondrial bioenergetics and the target of the antimalarial drug atovaquone that binds in the quinol oxidation (Qo) site of the complex. Structural analysis has shown that the Qo site residue Y279 (Y268 in Plasmodium falciparum) is key for atovaquone binding. Consequently, atovaquone resistance can be acquired by mutation of that residue. In addition to the probability of amino acid substitution, the level of atovaquone resistance and the loss of bc1 complex activity that are associated with the novel amino acid would restrict the nature of resistance-driven mutations occurring on atovaquone exposure in native parasite populations. Using the yeast model, we characterized the effect of all the amino acid replacements resulting from a single nucleotide substitution at codon 279: Y279C, Y279D, Y279F, Y279H, Y279N, and Y279S (Y279C, D, F, H, N, and S). Two residue changes that required a double nucleotide substitution, Y279A and W, were added to the series. We found that mutations Y279A, C, and S conferred high atovaquone resistance but decreased the catalytic activity. Y279F had wild-type enzymatic activity and sensitivity to atovaquone, while the other substitutions caused a dramatic respiratory defect. The results obtained with the yeast model were examined in regard to atomic structure and compared to the reported data on the evolution of acquired atovaquone resistance in P. falciparum.
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Pathological Mutations of the Mitochondrial Human Genome: the Instrumental Role of the Yeast S. cerevisiae. Diseases 2014. [DOI: 10.3390/diseases2010024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Meunier B, Fisher N, Ransac S, Mazat JP, Brasseur G. Respiratory complex III dysfunction in humans and the use of yeast as a model organism to study mitochondrial myopathy and associated diseases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1827:1346-61. [PMID: 23220121 DOI: 10.1016/j.bbabio.2012.11.015] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 11/21/2012] [Accepted: 11/28/2012] [Indexed: 11/25/2022]
Abstract
The bc1 complex or complex III is a central component of the aerobic respiratory chain in prokaryotic and eukaryotic organisms. It catalyzes the oxidation of quinols and the reduction of cytochrome c, establishing a proton motive force used to synthesize adenosine triphosphate (ATP) by the F1Fo ATP synthase. In eukaryotes, the complex III is located in the inner mitochondrial membrane. The genes coding for the complex III have a dual origin. While cytochrome b is encoded by the mitochondrial genome, all the other subunits are encoded by the nuclear genome. In this review, we compile an exhaustive list of the known human mutations and associated pathologies found in the mitochondrially-encoded cytochrome b gene as well as the fewer mutations in the nuclear genes coding for the complex III structural subunits and accessory proteins such as BCS1L involved in the assembly of the complex III. Due to the inherent difficulties of studying human biopsy material associated with complex III dysfunction, we also review the work that has been conducted to study the pathologies with the easy to handle eukaryotic microorganism, the yeast Saccharomyces cerevisiae. Phenotypes, biochemical data and possible effects due to the mutations are also discussed in the context of the known three-dimensional structure of the eukaryotic complex III. This article is part of a Special Issue entitled: Respiratory complex III and related bc complexes.
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Affiliation(s)
- B Meunier
- CNRS, Centre de Génétique Moléculaire, UPR 3404, Gif-sur-Yvette, F-91198, France
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Yang WC, Li H, Wang F, Zhu XL, Yang GF. Rieske Iron-Sulfur Protein of the Cytochrome bc1 Complex: A Potential Target for Fungicide Discovery. Chembiochem 2012; 13:1542-51. [DOI: 10.1002/cbic.201200295] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Indexed: 01/17/2023]
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Fisher N, Abd Majid R, Antoine T, Al-Helal M, Warman AJ, Johnson DJ, Lawrenson AS, Ranson H, O'Neill PM, Ward SA, Biagini GA. Cytochrome b mutation Y268S conferring atovaquone resistance phenotype in malaria parasite results in reduced parasite bc1 catalytic turnover and protein expression. J Biol Chem 2012; 287:9731-9741. [PMID: 22282497 PMCID: PMC3322985 DOI: 10.1074/jbc.m111.324319] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 01/26/2012] [Indexed: 11/24/2022] Open
Abstract
Atovaquone is an anti-malarial drug used in combination with proguanil (e.g. Malarone(TM)) for the curative and prophylactic treatment of malaria. Atovaquone, a 2-hydroxynaphthoquinone, is a competitive inhibitor of the quinol oxidation (Q(o)) site of the mitochondrial cytochrome bc(1) complex. Inhibition of this enzyme results in the collapse of the mitochondrial membrane potential, disruption of pyrimidine biosynthesis, and subsequent parasite death. Resistance to atovaquone in the field is associated with point mutations in the Q(o) pocket of cytochrome b, most notably near the conserved Pro(260)-Glu(261)-Trp(262)-Tyr(263) (PEWY) region in the ef loop). The effect of this mutation has been extensively studied in model organisms but hitherto not in the parasite itself. Here, we have performed a molecular and biochemical characterization of an atovaquone-resistant field isolate, TM902CB. Molecular analysis of this strain reveals the presence of the Y268S mutation in cytochrome b. The Y268S mutation is shown to confer a 270-fold shift of the inhibitory constant (K(i)) for atovaquone with a concomitant reduction in the V(max) of the bc(1) complex of ∼40% and a 3-fold increase in the observed K(m) for decylubiquinol. Western blotting analyses reveal a reduced iron-sulfur protein content in Y268S bc(1) suggestive of a weakened interaction between this subunit and cytochrome b. Gene expression analysis of the TM902CB strain reveals higher levels of expression, compared with the 3D7 (atovaquone-sensitive) control strain in bc(1) and cytochrome c oxidase genes. It is hypothesized that the observed differential expression of these and other key genes offsets the fitness cost resulting from reduced bc(1) activity.
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Affiliation(s)
- Nicholas Fisher
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - Roslaini Abd Majid
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - Thomas Antoine
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - Mohammed Al-Helal
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - Ashley J Warman
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - David J Johnson
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | | | - Hilary Ranson
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - Paul M O'Neill
- Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, United Kingdom
| | - Stephen A Ward
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and.
| | - Giancarlo A Biagini
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and.
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Van Nieuwenhuyse P, Van Leeuwen T, Khajehali J, Vanholme B, Tirry L. Mutations in the mitochondrial cytochrome b of Tetranychus urticae Koch (Acari: Tetranychidae) confer cross-resistance between bifenazate and acequinocyl. PEST MANAGEMENT SCIENCE 2009; 65:404-412. [PMID: 19165831 DOI: 10.1002/ps.1705] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
BACKGROUND Resistance of Tetranychus urticae Koch to bifenazate was recently linked with mutations in the mitochondrial cytochrome b Q(o) pocket, suggesting that bifenazate acts as a Q(o) inhibitor (Q(o)I). Since these mutations might cause cross-resistance to the known acaricidal Q(o)I acequinocyl and fluacrypyrim, resistance levels and inheritance patterns were investigated in several bifenazate-susceptible and bifenazate-resistant strains with different mutations in the cd1 and ef helices aligning the Q(o) pocket. RESULTS Cross-resistance to acequinocyl in two bifenazate-resistant strains was shown to be maternally inherited and caused by the combination of two specific mutations in the cytochrome b Q(o) pocket. Although most investigated strains were resistant to fluacrypyrim, resistance was not inherited maternally, but as a monogenic autosomal highly dominant trait. As a consequence, there was no correlation between cytochrome b genotype and fluacrypyrim resistance. CONCLUSIONS Although there is no absolute cross-resistance between bifenazate, acequinocyl and fluacrypyrim, some bifenazate resistance mutations confer cross-resistance to acequinocyl. In the light of resistance development and management, high prudence is called for when alternating bifenazate and acequinocyl in the same crop. Maternally inherited cross-resistance between bifenazate and acequinocyl reinforces the likelihood of bifenazate acting as a mitochondrial complex III inhibitor at the Q(o) site.
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Affiliation(s)
- Pieter Van Nieuwenhuyse
- Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B9000 Ghent, Belgium
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Seddiki N, Meunier B, Lemesle-Meunier D, Brasseur G. Is Cytochrome b Glutamic Acid 272 a Quinol Binding Residue in the bc1 Complex of Saccharomyces cerevisiae? Biochemistry 2008; 47:2357-68. [DOI: 10.1021/bi701905a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nadir Seddiki
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France, and Centre de Génétique Moléculaire, CNRS, UPR 2167, Gif-sur-Yvette, F-91198, France
| | - Brigitte Meunier
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France, and Centre de Génétique Moléculaire, CNRS, UPR 2167, Gif-sur-Yvette, F-91198, France
| | - Danielle Lemesle-Meunier
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France, and Centre de Génétique Moléculaire, CNRS, UPR 2167, Gif-sur-Yvette, F-91198, France
| | - Gaël Brasseur
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France, and Centre de Génétique Moléculaire, CNRS, UPR 2167, Gif-sur-Yvette, F-91198, France
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A structural perspective on mechanism and function of the cytochrome bc (1) complex. Results Probl Cell Differ 2007; 45:253-78. [PMID: 18038116 DOI: 10.1007/400_2007_042] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The cytochrome bc (1) complex is a fundamental component of the energy conversion machinery of respiratory and photosynthetic electron transfer chains. The multi-subunit membrane protein complex couples electron transfer from hydroquinone to cytochrome c to the translocation of protons across the membrane, thereby substantially contributing to the proton motive force that is used for ATP synthesis. Considerable progress has been made with structural and functional studies towards complete elucidation of the Q cycle mechanism, which was originally proposed by Mitchell 30 years ago. Yet, open questions regarding key steps of the mechanism still remain. The role of the complex as a major source of reactive oxygen species and its implication in pathophysiological conditions has recently gained interest.
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Forquer I, Covian R, Bowman MK, Trumpower BL, Kramer DM. Similar transition states mediate the Q-cycle and superoxide production by the cytochrome bc1 complex. J Biol Chem 2006; 281:38459-65. [PMID: 17008316 DOI: 10.1074/jbc.m605119200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cytochrome bc complexes found in mitochondria, chloroplasts and many bacteria play critical roles in their respective electron transport chains. The quinol oxidase (Q(o)) site in this complex oxidizes a hydroquinone (quinol), reducing two one-electron carriers, a low potential cytochrome b heme and the "Rieske" iron-sulfur cluster. The overall electron transfer reactions are coupled to transmembrane translocation of protons via a "Q-cycle" mechanism, which generates proton motive force for ATP synthesis. Since semiquinone intermediates of quinol oxidation are generally highly reactive, one of the key questions in this field is: how does the Q(o) site oxidize quinol without the production of deleterious side reactions including superoxide production? We attempt to test three possible general models to account for this behavior: 1) The Q(o) site semiquinone (or quinol-imidazolate complex) is unstable and thus occurs at a very low steady-state concentration, limiting O(2) reduction; 2) the Q(o) site semiquinone is highly stabilized making it unreactive toward oxygen; and 3) the Q(o) site catalyzes a quantum mechanically coupled two-electron/two-proton transfer without a semiquinone intermediate. Enthalpies of activation were found to be almost identical between the uninhibited Q-cycle and superoxide production in the presence of antimycin A in wild type. This behavior was also preserved in a series of mutants with altered driving forces for quinol oxidation. Overall, the data support models where the rate-limiting step for both Q-cycle and superoxide production is essentially identical, consistent with model 1 but requiring modifications to models 2 and 3.
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Affiliation(s)
- Isaac Forquer
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA
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Hagerman RA, Waring NJ, Willis RA, Hagerman AE. Ubiquinone accumulates in the mitochondria of yeast mutated in the ubiquinone binding protein, Qcr8p. Biochem Biophys Res Commun 2006; 344:241-5. [PMID: 16597436 DOI: 10.1016/j.bbrc.2006.03.110] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Accepted: 03/20/2006] [Indexed: 10/24/2022]
Abstract
In Saccharomyces cerevisiae, the trans-membrane helix of Qcr8p, the ubiquinone binding protein of complex III, contributes to the Q binding site. In wild-type cells, residue 62 of the helix is non-polar (proline). Substitution of proline 62 with a polar, uncharged residue does not impair the ability of the cells to respire, complex III assembly is unaffected, ubiquinone occupancy of the Q binding site is unchanged, and mitochondrial ubiquinone levels are in the wild-type range. Substitution with a +1 charged residue is associated with partial respiratory competence, impaired complex III assembly, and loss of cytochrome b. Although ubiquinone occupancy of the Q binding site is similar to wild-type, total mitochondrial ubiquinone doubled in these mutants. Mutants with a +2 charged substitution at position 62 are unable to respire. These results suggest that the accumulation of ubiquinone in the mitochondria may be a compensatory mechanism for impaired electron transport at cytochrome b.
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Affiliation(s)
- Ruth A Hagerman
- School of Biological Sciences, University of Texas at Austin, Austin, TX 78712, USA.
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15
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Cape JL, Strahan JR, Lenaeus MJ, Yuknis BA, Le TT, Shepherd JN, Bowman MK, Kramer DM. The respiratory substrate rhodoquinol induces Q-cycle bypass reactions in the yeast cytochrome bc(1) complex: mechanistic and physiological implications. J Biol Chem 2005; 280:34654-60. [PMID: 16087663 DOI: 10.1074/jbc.m507616200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial cytochrome bc(1) complex catalyzes the transfer of electrons from ubiquinol to cyt c while generating a proton motive force for ATP synthesis via the "Q-cycle" mechanism. Under certain conditions electron flow through the Q-cycle is blocked at the level of a reactive intermediate in the quinol oxidase site of the enzyme, resulting in "bypass reactions," some of which lead to superoxide production. Using analogs of the respiratory substrates ubiquinol-3 and rhodoquinol-3, we show that the relative rates of Q-cycle bypass reactions in the Saccharomyces cerevisiae cyt bc(1) complex are highly dependent by a factor of up to 100-fold on the properties of the substrate quinol. Our results suggest that the rate of Q-cycle bypass reactions is dependent on the steady state concentration of reactive intermediates produced at the quinol oxidase site of the enzyme. We conclude that normal operation of the Q-cycle requires a fairly narrow window of redox potentials with respect to the quinol substrate to allow normal turnover of the complex while preventing potentially damaging bypass reactions.
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Affiliation(s)
- Jonathan L Cape
- Institute of Biological Chemistry, Washingston State University, Pullman, Washington 99164-6340, USA
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16
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Current awareness on yeast. Yeast 2004; 21:1317-24. [PMID: 15586969 DOI: 10.1002/yea.1097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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