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Abstract
Mitochondria are dynamic organelles vital for energy production with now appreciated roles in immune defense. During microbial infection, mitochondria serve as signaling hubs to induce immune responses to counteract invading pathogens like viruses. Mitochondrial functions are central to a variety of antiviral responses including apoptosis and type I interferon signaling (IFN-I). While apoptosis and IFN-I mediated by mitochondrial antiviral signaling (MAVS) are well-established defenses, new dimensions of mitochondrial biology are emerging as battlefronts during viral infection. Increasingly, it has become apparent that mitochondria serve as reservoirs for distinct cues that trigger immune responses and that alterations in mitochondrial morphology may also tip infection outcomes. Furthermore, new data are foreshadowing pivotal roles for classic, homeostatic facets of this organelle as host-virus interfaces, namely, the tricarboxylic acid (TCA) cycle and electron transport chain (ETC) complexes like respiratory supercomplexes. Underscoring the importance of "housekeeping" mitochondrial activities in viral infection is the growing list of viral-encoded inhibitors including mimics derived from cellular genes that antagonize these functions. For example, virologs for ETC factors and several enzymes from the TCA cycle have been recently identified in DNA virus genomes and serve to pinpoint new vulnerabilities during infection. Here, we highlight recent advances for known antiviral functions associated with mitochondria as well as where the next battlegrounds may be based on viral effectors. Collectively, new methodology and mechanistic insights over the coming years will strengthen our understanding of how an ancient molecular truce continues to defend cells against viruses.
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Affiliation(s)
- Mahsa Sorouri
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Tyron Chang
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Genetics, Disease, and Development Graduate Program, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Dustin C Hancks
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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2
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Duong QV, Levitsky Y, Dessinger MJ, Strubbe-Rivera JO, Bazil JN. Identifying Site-Specific Superoxide and Hydrogen Peroxide Production Rates From the Mitochondrial Electron Transport System Using a Computational Strategy. FUNCTION (OXFORD, ENGLAND) 2021; 2:zqab050. [PMID: 35330793 PMCID: PMC8788716 DOI: 10.1093/function/zqab050] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 08/02/2021] [Accepted: 09/14/2021] [Indexed: 01/07/2023]
Abstract
Mitochondrial reactive oxygen species (ROS) play important roles in cellular signaling; however, certain pathological conditions such as ischemia/reperfusion (I/R) injury disrupt ROS homeostasis and contribute to cell death. A major impediment to developing therapeutic measures against oxidative stress-induced cellular damage is the lack of a quantitative framework to identify the specific sources and regulatory mechanisms of mitochondrial ROS production. We developed a thermodynamically consistent, mass-and-charge balanced, kinetic model of mitochondrial ROS homeostasis focused on redox sites of electron transport chain complexes I, II, and III. The model was calibrated and corroborated using comprehensive data sets relevant to ROS homeostasis. The model predicts that complex I ROS production dominates other sources under conditions favoring a high membrane potential with elevated nicotinamide adenine dinucleotide (NADH) and ubiquinol (QH2) levels. In general, complex I contributes to significant levels of ROS production under pathological conditions, while complexes II and III are responsible for basal levels of ROS production, especially when QH2 levels are elevated. The model also reveals that hydrogen peroxide production by complex I underlies the non-linear relationship between ROS emission and O2 at low O2 concentrations. Lastly, the model highlights the need to quantify scavenging system activity under different conditions to establish a complete picture of mitochondrial ROS homeostasis. In summary, we describe the individual contributions of the electron transport system complex redox sites to total ROS emission in mitochondria respiring under various combinations of NADH- and Q-linked respiratory fuels under varying workloads.
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Affiliation(s)
- Quynh V Duong
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA
| | - Yan Levitsky
- Department of Physiology, Michigan State University, East Lansing, Michigan 48824, USA
| | - Maria J Dessinger
- Department of Physiology, Michigan State University, East Lansing, Michigan 48824, USA
| | - Jasiel O Strubbe-Rivera
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan 48824, USA
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Kalmar B, Innes A, Wanisch K, Kolaszynska AK, Pandraud A, Kelly G, Abramov AY, Reilly MM, Schiavo G, Greensmith L. Mitochondrial deficits and abnormal mitochondrial retrograde axonal transport play a role in the pathogenesis of mutant Hsp27-induced Charcot Marie Tooth Disease. Hum Mol Genet 2018; 26:3313-3326. [PMID: 28595321 PMCID: PMC5808738 DOI: 10.1093/hmg/ddx216] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 05/25/2017] [Indexed: 11/26/2022] Open
Abstract
Mutations in the small heat shock protein Hsp27, encoded by the HSPB1 gene, have been shown to cause Charcot Marie Tooth Disease type 2 (CMT-2) or distal hereditary motor neuropathy (dHMN). Protein aggregation and axonal transport deficits have been implicated in the disease. In this study, we conducted analysis of bidirectional movements of mitochondria in primary motor neuron axons expressing wild type and mutant Hsp27. We found significantly slower retrograde transport of mitochondria in Ser135Phe, Pro39Leu and Arg140Gly mutant Hsp27 expressing motor neurons than in wild type Hsp27 neurons, although anterograde movement velocities remained normal. Retrograde transport of other important cargoes, such as the p75 neurotrophic factor receptor was minimally altered in mutant Hsp27 neurons, implicating that axonal transport deficits primarily affect mitochondria and the axonal transport machinery itself is less affected. Investigation of mitochondrial function revealed a decrease in mitochondrial membrane potential in mutant Hsp27 expressing motor axons, as well as a reduction in mitochondrial complex 1 activity, increased vulnerability of mitochondria to mitochondrial stressors, leading to elevated superoxide release and reduced mitochondrial glutathione (GSH) levels, although cytosolic GSH remained normal. This mitochondrial redox imbalance in mutant Hsp27 motor neurons is likely to cause low level of oxidative stress, which in turn will contribute to, and indeed may be the underlying cause of the deficits in mitochondrial axonal transport. Together, these findings suggest that the mitochondrial abnormalities in mutant Hsp27-induced neuropathies may be a primary cause of pathology, leading to further deficits in the mitochondrial axonal transport and onset of disease.
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Affiliation(s)
| | - Amy Innes
- Sobell Department of Motor Neuroscience and Movement Disorders.,MRC Centre for Neuromuscular Diseases
| | - Klaus Wanisch
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square House, Queen Square, London WC1N 3BG, UK
| | | | - Amelie Pandraud
- MRC Centre for Neuromuscular Diseases.,Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square House, Queen Square, London WC1N 3BG, UK
| | - Gavin Kelly
- Bioinformatics and Biostatistics Science Technology Platform, The Francis Crick Institute, London NW1?1AT, UK
| | | | - Mary M Reilly
- MRC Centre for Neuromuscular Diseases.,Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square House, Queen Square, London WC1N 3BG, UK
| | | | - Linda Greensmith
- Sobell Department of Motor Neuroscience and Movement Disorders.,MRC Centre for Neuromuscular Diseases
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Analysis of a Functional Dimer Model of Ubiquinol Cytochrome c Oxidoreductase. Biophys J 2017; 113:1599-1612. [PMID: 28978450 PMCID: PMC5627346 DOI: 10.1016/j.bpj.2017.08.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 08/04/2017] [Accepted: 08/10/2017] [Indexed: 11/21/2022] Open
Abstract
Ubiquinol cytochrome c oxidoreductase (bc1 complex) serves as an important electron junction in many respiratory systems. It funnels electrons coming from NADH and ubiquinol to cytochrome c, but it is also capable of producing significant amounts of the free radical superoxide. In situ and in other experimental systems, the enzyme exists as a dimer. But until recently, it was believed to operate as a functional monomer. Here we show that a functional dimer model is capable of explaining both kinetic and superoxide production rate data. The model consists of six electronic states characterized by the number of electrons deposited on the complex. It is fully reversible and strictly adheres to the thermodynamics governing the reactions. A total of nine independent data sets were used to parameterize the model. To explain the data with a consistent set of parameters, it was necessary to incorporate intramonomer Coulombic effects between hemes bL and bH and intermonomer Coulombic effects between bL hemes. The fitted repulsion energies fall within the theoretical range of electrostatic calculations. In addition, model analysis demonstrates that the Q pool is mostly oxidized under normal physiological operation but can switch to a more reduced state when reverse electron transport conditions are in place.
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Analysis of the kinetics and bistability of ubiquinol:cytochrome c oxidoreductase. Biophys J 2014; 105:343-55. [PMID: 23870256 DOI: 10.1016/j.bpj.2013.05.033] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 03/28/2013] [Accepted: 05/13/2013] [Indexed: 11/21/2022] Open
Abstract
Ubiquinol:cytochrome c oxidoreductase, bc1 complex, is the enzyme in the respiratory chain of mitochondria responsible for the transfer reducing potential from ubiquinol to cytochrome c coupled to the movement of charge against the electrostatic potential across the mitochondrial inner membrane. The complex is also implicated in the generation of reactive oxygen species under certain conditions and is thus a contributor to cellular oxidative stress. Here, a biophysically detailed, thermodynamically consistent model of the bc1 complex for mammalian mitochondria is developed. The model incorporates the major redox centers near the Qo- and Qi-site of the enzyme, includes the pH-dependent redox reactions, accounts for the effect of the proton-motive force of the reaction rate, and simulates superoxide production at the Qo-site. The model consists of six distinct states characterized by the mobile electron distribution in the enzyme. Within each state, substates that correspond to various electron localizations exist in a rapid equilibrium distribution. The steady-state equation for the six-state system is parameterized using five independent data sets and validated in comparison to additional experimental data. Model analysis suggests that the pH-dependence on turnover is primarily due to the pKa values of cytochrome bH and Rieske iron sulfur protein. A previously proposed kinetic scheme at the Qi-site where ubiquinone binds to only the reduced enzyme and ubiquinol binds to only the oxidized enzyme is shown to be thermodynamically infeasible. Moreover, the model is able to reproduce the bistability phenomenon where at a given overall flux through the enzyme, different rates of superoxide production are attained when the enzyme is differentially reduced.
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Yoon H, Kim DS, Lee GH, Kim KW, Kim HR, Chae HJ. Apoptosis Induced by Manganese on Neuronal SK-N-MC Cell Line: Endoplasmic Reticulum (ER) Stress and Mitochondria Dysfunction. ENVIRONMENTAL HEALTH AND TOXICOLOGY 2011; 26:e2011017. [PMID: 22232721 PMCID: PMC3250590 DOI: 10.5620/eht.2011.26.e2011017] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2011] [Accepted: 11/11/2011] [Indexed: 05/31/2023]
Abstract
OBJECTIVES Manganese chloride (MnCl(2)) is one of heavy metals for causing neurogenerative dysfunction like Manganism. The purpose of this study was to determine the acute toxicity of MnCl(2) using different times and various concentrations including whether manganese toxicity may involve in two intrinsic pathways, endoplasmic reticulum (ER) stress and mitochondria dysfunction and lead to neuronal apoptosis mediated by organelle disorders in neuroblastoma cell line SK-N-MC. METHODS In the acute toxicity test, five concentrations (200, 400, 600, 800, 1,000 uM) of MnCl(2) with 3, 6, 12, 24, 48 hours exposure were selected to analyze cell viability. In addition, to better understand their toxicity, acute toxicity was examined with 1,000 uM MnCl(2) for 24 hours exposure via reactive oxygen species (ROS), mitochondria membrane potential, western blotting and mitochondrial complex activities. RESULTS Our results showed that both increments of dose and time prompt the increments in the number of dead cells. Cells treated by 1,000 µM MnCl(2) activated 265% (±8.1) caspase-3 compared to control cell. MnCl(2) induced intracellular ROS produced 168% (±2.3%) compared to that of the control cells and MnCl(2) induced neurotoxicity significantly dissipated 48.9% of mitochondria membrane potential compared to the control cells. CONCLUSIONS This study indicated that MnCl(2) induced apoptosis via ER stress and mitochondria dysfunction. In addition, MnCl(2) affected only complex I except complex II, III or IV activities.
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Affiliation(s)
- Hyonok Yoon
- Department of Pharmacology, School of Medicine, Chonbuk National University, Jeonju, Korea
- School of Pharmacy, Howard University, Washington DC, USA
| | - Do-Sung Kim
- Department of Pharmacology, School of Medicine, Chonbuk National University, Jeonju, Korea
| | - Geum-Hwa Lee
- Department of Pharmacology, School of Medicine, Chonbuk National University, Jeonju, Korea
| | - Kee-Won Kim
- Department of Pharmacology, School of Medicine, Chonbuk National University, Jeonju, Korea
| | | | - Han-Jung Chae
- Department of Pharmacology, School of Medicine, Chonbuk National University, Jeonju, Korea
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Yoon H, Lee GH, Kim DS, Kim KW, Kim HR, Chae HJ. The effects of 3, 4 or 5 amino salicylic acids on manganese-induced neuronal death: ER stress and mitochondrial complexes. Toxicol In Vitro 2011; 25:1259-68. [DOI: 10.1016/j.tiv.2011.04.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 03/07/2011] [Accepted: 04/01/2011] [Indexed: 02/02/2023]
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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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9
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Jarmuszkiewicz W, Sluse-Goffart CM, Hryniewiecka L, Michejda J, Sluse FE. Electron partitioning between the two branching quinol-oxidizing pathways in Acanthamoeba castellanii mitochondria during steady-state state 3 respiration. J Biol Chem 1998; 273:10174-80. [PMID: 9553066 DOI: 10.1074/jbc.273.17.10174] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Amoeba mitochondria possess a respiratory chain with two quinol-oxidizing pathways: the cytochrome pathway and the cyanide-resistant alternative oxidase pathway. The ADP/O method, based on the non-phosphorylating property of alternative oxidase, was used to determine contributions of both pathways in overall state 3 respiration in the presence of GMP (an activator of the alternative oxidase in amoeba) and succinate as oxidizable substrate. This method involves pair measurements of ADP/O ratios plus and minus benzohydroxamate (an inhibitor of the alternative oxidase). The requirements of the method are listed and verified. When overall state 3 respiration was decreased by increasing concentrations of n-butyl malonate (a non-penetrating inhibitor of succinate uptake), the quinone reduction level declined. At the same time, the alternative pathway contribution decreased sharply and became negligible when quinone redox state was lower than 50%, whereas the cytochrome pathway contribution first increased and then passed through a maximum at a quinone redox state of 58% and sharply decreased at a lower level of quinone reduction. This study is the first attempt to examine the steady-state kinetics of the two quinol-oxidizing pathways when both are active and to describe electron partitioning between them when the steady-state rate of the quinone-reducing pathway is varied.
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Affiliation(s)
- W Jarmuszkiewicz
- Department of Bioenergetics, Adam Mickiewicz University, Fredry 10, 61-701 Poznan, Poland.
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10
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Krab K. Kinetic and regulatory aspects of the function of the alternative oxidase in plant respiration. J Bioenerg Biomembr 1995; 27:387-96. [PMID: 8595974 DOI: 10.1007/bf02110001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The kinetic modelling of the respiratory network in plant mitochondria is discussed, with emphasis on the importance of the choice of boundary conditions, and of modelling of both quinol-oxidising and quinone-reducing pathways. This allows quantitative understanding of the interplay between the different pathways, and of the functioning of the plant respiratory network in terms of the kinetic properties of its component parts. The effects of activation of especially succinate dehydrogenase and the cyanide-insensitive alternative oxidase are discussed. Phenomena, such as respiratory control ratios depending on the substrate, shortcomings of the Bahr and Bonner model for electron distribution between the oxidases and reversed respiratory control, are explained. The relation to metabolic control analysis of the respiratory network is discussed in terms of top-down analysis.
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Affiliation(s)
- K Krab
- Department of Molecular and Cellular Biology, Vrije Universiteit, Amsterdam, The Netherlands
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11
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Van den Bergen CW, Wagner AM, Krab K, Moore AL. The relationship between electron flux and the redox poise of the quinone pool in plant mitochondria. Interplay between quinol-oxidizing and quinone-reducing pathways. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 226:1071-8. [PMID: 7813462 DOI: 10.1111/j.1432-1033.1994.01071.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The dependence of electron flux through quinone-reducing and quinol-oxidizing pathways on the redox state of the ubiquinone (Q) pool was investigated in plant mitochondria isolated from potato (Solanum tuberosum cv. Bintje, fresh tissue and callus), sweet potato (Ipomoea batatas) and Arum italicum. We have determined the redox state of the Q pool with two different methods, the Q-electrode and Q-extraction techniques. Although results from the two techniques agree well, in all tissues tested (with the exception of fresh potato) an inactive pool of QH2 was detected by the extraction technique that was not observed with the electrode. In potato callus mitochondria, an inactive Q pool was also found. An advantage of the extraction method is that it permits determination of the Q redox state in the presence of substances that interfere with the Q-electrode, such as benzohydroxamate and NADH. We have studied the relation between rate and Q redox state for both quinol-oxidizing and quinone-reducing pathways under a variety of metabolic conditions including state 3, state 4, in the presence of myxothiazol, and benzohydroxamate. Under state 4 conditions or in the presence of myxothiazol, a non-linear dependence of the rate of respiration on the Q-redox state was observed in potato callus mitochondria and in sweet potato mitochondria. The addition of benzohydroxamate, under state 4 conditions, removed this non-linearity confirming that it is due to activity of the cyanide-resistant pathway. The relation between rate and Q redox state for the external NADH dehydrogenase in potato callus mitochondria was found to differ from that of succinate dehydrogenase. It is suggested that the oxidation of cytoplasmic NADH in vivo uses the cyanide-resistant pathway more than the pathway involving the oxidation of succinate. A model is used to predict the kinetic behaviour of the respiratory network. It is shown that titrations with inhibitors of the alternative oxidase cannot be used to demonstrate a pure overflow function of the alternative oxidase.
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Affiliation(s)
- C W Van den Bergen
- Department of Molecular and Cellular Biology, Vrije Universiteit, Amsterdam, The Netherlands
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12
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Moore AL, Leach G, Whitehouse DG, van den Bergen CW, Wagner AM, Krab K. Control of oxidative phosphorylation in plant mitochondria: The role of non-phosphorylating pathways. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1994. [DOI: 10.1016/0005-2728(94)90101-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Siedow JN, Moore AL. A kinetic model for the regulation of electron transfer through the cyanide-resistant pathway in plant mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1993. [DOI: 10.1016/0005-2728(93)90098-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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14
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Moore AL, Siedow JN. The regulation and nature of the cyanide-resistant alternative oxidase of plant mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1059:121-40. [PMID: 1883834 DOI: 10.1016/s0005-2728(05)80197-5] [Citation(s) in RCA: 247] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In addition to possessing multiple NAD(P)H dehydrogenases, most plant mitochondria contain a cyanide- and antimycin-insensitive alternative terminal oxidase. Although the general characteristics of this terminal oxidase have been known for a considerable number of years, the mechanism by which it is regulated is unclear and until recently there has been relatively little information on its exact nature. In the past 5 years, however, the application of molecular and novel voltametric techniques has advanced our understanding of this oxidase considerably. In this article, we review briefly current understanding on the structure and function of the multiple NADH dehydrogenases and consider, in detail, the nature and regulation of the alternative oxidase. We derive a kinetic model for electron transfer through the ubiquinone pool based on a proposed model for the reduction of the oxidase by quinol and show how this can account for deviations from Q-pool behaviour. We review information on the attempts to isolate and characterise the oxidase and finally consider the molecular aspects of the expression of the alternative oxidase.
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Affiliation(s)
- A L Moore
- Department of Biochemistry, University of Sussex, Brighton, U.K
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15
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Camougrand NM, Zniber S, Guérin MG. The antimycin-A-insensitive respiratory pathway of Candida parapsilosis: evidence for a second quinone involved specifically in its functioning. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1057:124-30. [PMID: 2009273 DOI: 10.1016/s0005-2728(05)80092-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The involvement of a quinone in the antimycin A-insensitive electron transfer from NADH-dehydrogenase to cytochrome c via the alternative respiratory chain of Candida parapsilosis, by-passing complex II, has been studied. After a partial extraction of quinones, the residual respiration was fully antimycin-A-sensitive, but reincorporation of the organic extract partially restored an antimycin A-insensitive respiration. Analysis of quinone content by HPLC, after purification by thin-layer chromatography, evidenced another quinone species in a very low amount. Myxothiazol and stigmatellin were shown to inhibit the alternative pathway but at a higher concentration than required to inhibit the classical pathway. Cytochrome spectra analysis showed that, in the presence of high myxothiazol concentrations, cytochromes c and aa3 were not reduced, while they were in the presence of antimycin A. It is suggested that the secondary pathway of C. parapsilosis involved a specific quinone pool which can be displaced from its binding site by high concentrations of myxothiazol or analogous compounds.
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Affiliation(s)
- N M Camougrand
- Institut de Biochimie Cellulaire et Neurochimie du CNRS, Université de Bordeaux II, France
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16
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Day DA, Dry IB, Soole KL, Wiskich JT, Moore AL. Regulation of Alternative Pathway Activity in Plant Mitochondria : Deviations from Q-Pool Behavior during Oxidation of NADH and Quinols. PLANT PHYSIOLOGY 1991; 95:948-53. [PMID: 16668077 PMCID: PMC1077629 DOI: 10.1104/pp.95.3.948] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
External NADH and succinate were oxidized at similar rates by soybean (Glycine max) cotyledon and leaf mitochondria when the cytochrome chain was operating, but the rate of NADH oxidation via the alternative oxidase was only half that of succinate. However, measurements of the redox poise of the endogenous quinone pool and reduction of added quinones revealed that external NADH reduced them to the same, or greater, extent than did succinate. A kinetic analysis of the relationship between alternative oxidase activity and the redox state of ubiquinone indicated that the degree of ubiquinone reduction during external NADH oxidation was sufficient to fully engage the alternative oxidase. Measurements of NADH oxidation in the presence of succinate showed that the two substrates competed for cytochrome chain activity but not for alternative oxidase activity. Both reduced Q-1 and duroquinone were readily oxidized by the cytochrome oxidase pathway but only slowly by the alternative oxidase pathway in soybean mitochondria. In mitochondria isolated from the thermogenic spadix of Philodendron selloum, on the other hand, quinol oxidation via the alternative oxidase was relatively rapid; in these mitochondria, external NADH was also oxidized readily by the alternative oxidase. Antibodies raised against alternative oxidase proteins from Sauromatum guttatum cross-reacted with proteins of similar molecular size from soybean mitochondria, indicating similarities between the two alternative oxidases. However, it appears that the organization of the respiratory chain in soybean is different, and we suggest that some segregation of electron transport chain components may exist in mitochondria from nonthermogenic plant tissues.
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Affiliation(s)
- D A Day
- Botany Department, Australian National University, Canberra, A. C. T. 2601
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17
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Zannoni D, Moore AL. Measurement of the redox state of the ubiquinone pool in Rhodobacter capsulatus membrane fragments. FEBS Lett 1990; 271:123-7. [PMID: 2171997 DOI: 10.1016/0014-5793(90)80387-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The dependence of the respiratory rate on the redox poise of the quinone pool was investigated in wild type and mutant membranes of Rhodobacter capsulatus. A linear relationship has been found between these two parameters only when succinate was oxidized by the bc1 complex. Conversely, a marked nonlinear relationship was observed between the Q-pool reduction level and the respiratory rate when O2 uptake occurred via the alternative oxidase. In addition, it was found that this latter pathway was not engaged until Q-pool reduction level reached approximately 25%. These results are discussed within the framework of a homogeneous pool regulating both photosynthetic and respiratory fluxes.
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Affiliation(s)
- D Zannoni
- Department of Biology, University of Bologna, Italy
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18
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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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