1
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Pereira CS, Teixeira MH, Russell DA, Hirst J, Arantes GM. Mechanism of rotenone binding to respiratory complex I depends on ligand flexibility. Sci Rep 2023; 13:6738. [PMID: 37185607 PMCID: PMC10130173 DOI: 10.1038/s41598-023-33333-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 04/11/2023] [Indexed: 05/17/2023] Open
Abstract
Respiratory complex I is a major cellular energy transducer located in the inner mitochondrial membrane. Its inhibition by rotenone, a natural isoflavonoid, has been used for centuries by indigenous peoples to aid in fishing and, more recently, as a broad-spectrum pesticide or even a possible anticancer therapeutic. Unraveling the molecular mechanism of rotenone action will help to design tuned derivatives and to understand the still mysterious catalytic mechanism of complex I. Although composed of five fused rings, rotenone is a flexible molecule and populates two conformers, bent and straight. Here, a rotenone derivative locked in the straight form was synthesized and found to inhibit complex I with 600-fold less potency than natural rotenone. Large-scale molecular dynamics and free energy simulations of the pathway for ligand binding to complex I show that rotenone is more stable in the bent conformer, either free in the membrane or bound to the redox active site in the substrate-binding Q-channel. However, the straight conformer is necessary for passage from the membrane through the narrow entrance of the channel. The less potent inhibition of the synthesized derivative is therefore due to its lack of internal flexibility, and interconversion between bent and straight forms is required to enable efficient kinetics and high stability for rotenone binding. The ligand also induces reconfiguration of protein loops and side-chains inside the Q-channel similar to structural changes that occur in the open to closed conformational transition of complex I. Detailed understanding of ligand flexibility and interactions that determine rotenone binding may now be exploited to tune the properties of synthetic derivatives for specific applications.
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Affiliation(s)
- Caroline S Pereira
- Department of Biochemistry, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, São Paulo, SP, 05508-900, Brazil
| | - Murilo H Teixeira
- Department of Biochemistry, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, São Paulo, SP, 05508-900, Brazil
| | - David A Russell
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Judy Hirst
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, UK.
| | - Guilherme M Arantes
- Department of Biochemistry, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, São Paulo, SP, 05508-900, Brazil.
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2
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Stuchebrukhov AA, Hayashi T. Single protonation of the reduced quinone in respiratory complex I drives four-proton pumping. FEBS Lett 2023; 597:237-245. [PMID: 36251339 PMCID: PMC9877130 DOI: 10.1002/1873-3468.14518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 10/02/2022] [Accepted: 10/03/2022] [Indexed: 01/29/2023]
Abstract
Complex I is a key proton-pumping enzyme in bacterial and mitochondrial respiratory electron transport chains. Using quantum chemistry and electrostatic calculations, we have examined the pKa of the reduced quinone QH-/QH2 in the catalytic cavity of complex I. We find that pKa (QH-/QH2) is very high, above 20. This means that the energy of a single protonation reaction of the doubly reduced quinone (i.e. the reduced semiquinone QH-) is sufficient to drive four protons across the membrane with a potential of 180 mV. Based on these calculations, we propose a possible scheme of redox-linked proton pumping by complex I. The model explains how the energy of the protonation reaction can be divided equally among four pumping units of the pump, and how a single proton can drive translocation of four additional protons in multiple pumping blocks.
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Affiliation(s)
| | - Tomoyuki Hayashi
- Department of Chemistry, University of California, Davis, CA 95616
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3
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Kampjut D, Sazanov LA. Structure of respiratory complex I – An emerging blueprint for the mechanism. Curr Opin Struct Biol 2022; 74:102350. [PMID: 35316665 PMCID: PMC7613608 DOI: 10.1016/j.sbi.2022.102350] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 01/25/2022] [Accepted: 02/08/2022] [Indexed: 11/26/2022]
Abstract
Complex I is one of the major respiratory complexes, conserved from bacteria to mammals. It oxidises NADH, reduces quinone and pumps protons across the membrane, thus playing a central role in the oxidative energy metabolism. In this review we discuss our current state of understanding the structure of complex I from various species of mammals, plants, fungi, and bacteria, as well as of several complex I-related proteins. By comparing the structural evidence from these systems in different redox states and data from mutagenesis and molecular simulations, we formulate the mechanisms of electron transfer and proton pumping and explain how they are conformationally and electrostatically coupled. Finally, we discuss the structural basis of the deactivation phenomenon in mammalian complex I.
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4
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Richardson KH, Wright JJ, Šimėnas M, Thiemann J, Esteves AM, McGuire G, Myers WK, Morton JJL, Hippler M, Nowaczyk MM, Hanke GT, Roessler MM. Functional basis of electron transport within photosynthetic complex I. Nat Commun 2021; 12:5387. [PMID: 34508071 PMCID: PMC8433477 DOI: 10.1038/s41467-021-25527-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 08/11/2021] [Indexed: 02/08/2023] Open
Abstract
Photosynthesis and respiration rely upon a proton gradient to produce ATP. In photosynthesis, the Respiratory Complex I homologue, Photosynthetic Complex I (PS-CI) is proposed to couple ferredoxin oxidation and plastoquinone reduction to proton pumping across thylakoid membranes. However, little is known about the PS-CI molecular mechanism and attempts to understand its function have previously been frustrated by its large size and high lability. Here, we overcome these challenges by pushing the limits in sample size and spectroscopic sensitivity, to determine arguably the most important property of any electron transport enzyme - the reduction potentials of its cofactors, in this case the iron-sulphur clusters of PS-CI (N0, N1 and N2), and unambiguously assign them to the structure using double electron-electron resonance. We have thus determined the bioenergetics of the electron transfer relay and provide insight into the mechanism of PS-CI, laying the foundations for understanding of how this important bioenergetic complex functions.
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Affiliation(s)
- Katherine H. Richardson
- grid.4868.20000 0001 2171 1133School of Biological and Chemical Sciences, Queen Mary University of London, London, UK ,grid.7445.20000 0001 2113 8111Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, London, UK
| | - John J. Wright
- grid.4868.20000 0001 2171 1133School of Biological and Chemical Sciences, Queen Mary University of London, London, UK ,grid.14105.310000000122478951Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Cambridge, UK
| | - Mantas Šimėnas
- grid.83440.3b0000000121901201London Centre for Nanotechnology, University College London, London, UK
| | - Jacqueline Thiemann
- grid.5570.70000 0004 0490 981XPlant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Ana M. Esteves
- grid.4868.20000 0001 2171 1133School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
| | - Gemma McGuire
- grid.4868.20000 0001 2171 1133School of Biological and Chemical Sciences, Queen Mary University of London, London, UK ,grid.7445.20000 0001 2113 8111Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, London, UK
| | - William K. Myers
- grid.4991.50000 0004 1936 8948Inorganic Chemistry, University of Oxford, Oxford, UK
| | - John J. L. Morton
- grid.83440.3b0000000121901201London Centre for Nanotechnology, University College London, London, UK ,grid.83440.3b0000000121901201Department of Electronic & Electrical Engineering, UCL, London, UK
| | - Michael Hippler
- grid.5949.10000 0001 2172 9288Institute of Plant Biology and Biotechnology, University of Münster, Münster, Germany ,grid.261356.50000 0001 1302 4472Institute of Plant Science and Resources, Okayama University, Kurashiki, Japan
| | - Marc M. Nowaczyk
- grid.5570.70000 0004 0490 981XPlant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Guy T. Hanke
- grid.4868.20000 0001 2171 1133School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
| | - Maxie M. Roessler
- grid.7445.20000 0001 2113 8111Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, London, UK
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5
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Moosmann B, Schindeldecker M, Hajieva P. Cysteine, glutathione and a new genetic code: biochemical adaptations of the primordial cells that spread into open water and survived biospheric oxygenation. Biol Chem 2021; 401:213-231. [PMID: 31318686 DOI: 10.1515/hsz-2019-0232] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2019] [Accepted: 07/08/2019] [Indexed: 12/13/2022]
Abstract
Life most likely developed under hyperthermic and anaerobic conditions in close vicinity to a stable geochemical source of energy. Epitomizing this conception, the first cells may have arisen in submarine hydrothermal vents in the middle of a gradient established by the hot and alkaline hydrothermal fluid and the cooler and more acidic water of the ocean. To enable their escape from this energy-providing gradient layer, the early cells must have overcome a whole series of obstacles. Beyond the loss of their energy source, the early cells had to adapt to a loss of external iron-sulfur catalysis as well as to a formidable temperature drop. The developed solutions to these two problems seem to have followed the principle of maximum parsimony: Cysteine was introduced into the genetic code to anchor iron-sulfur clusters, and fatty acid unsaturation was installed to maintain lipid bilayer viscosity. Unfortunately, both solutions turned out to be detrimental when the biosphere became more oxidizing after the evolution of oxygenic photosynthesis. To render cysteine thiol groups and fatty acid unsaturation compatible with life under oxygen, numerous counter-adaptations were required including the advent of glutathione and the addition of the four latest amino acids (methionine, tyrosine, tryptophan, selenocysteine) to the genetic code. In view of the continued diversification of derived antioxidant mechanisms, it appears that modern life still struggles with the initially developed strategies to escape from its hydrothermal birthplace. Only archaea may have found a more durable solution by entirely exchanging their lipid bilayer components and rigorously restricting cysteine usage.
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Affiliation(s)
- Bernd Moosmann
- Evolutionary Biochemistry and Redox Medicine, Institute for Pathobiochemistry, University Medical Center of the Johannes Gutenberg University, D-55128 Mainz, Germany
| | - Mario Schindeldecker
- Evolutionary Biochemistry and Redox Medicine, Institute for Pathobiochemistry, University Medical Center of the Johannes Gutenberg University, D-55128 Mainz, Germany
| | - Parvana Hajieva
- Cellular Adaptation Group, Institute for Pathobiochemistry, University Medical Center of the Johannes Gutenberg University, D-55128 Mainz, Germany
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6
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Pamplona R, Jové M, Mota-Martorell N, Barja G. Is the NDUFV2 subunit of the hydrophilic complex I domain a key determinant of animal longevity? FEBS J 2021; 288:6652-6673. [PMID: 33455045 DOI: 10.1111/febs.15714] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 12/02/2020] [Accepted: 01/14/2021] [Indexed: 12/18/2022]
Abstract
Complex I, a component of the electron transport chain, plays a central functional role in cell bioenergetics and the biology of free radicals. The structural and functional N module of complex I is one of the main sites of the generation of free radicals. The NDUFV2 subunit/N1a cluster is a component of this module. Furthermore, the rate of free radical production is linked to animal longevity. In this review, we explore the hypothesis that NDUFV2 is the only conserved core subunit designed with a regulatory function to ensure correct electron transfer and free radical production, that low gene expression and protein abundance of the NDUFV2 subunit is an evolutionary adaptation needed to achieve a longevity phenotype, and that these features are determinants of the lower free radical generation at the mitochondrial level and a slower rate of aging of long-lived animals.
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Affiliation(s)
- Reinald Pamplona
- Department of Experimental Medicine, University of Lleida-Lleida Biomedical Research Institute (UdL-IRBLleida), Lleida, Spain
| | - Mariona Jové
- Department of Experimental Medicine, University of Lleida-Lleida Biomedical Research Institute (UdL-IRBLleida), Lleida, Spain
| | - Natalia Mota-Martorell
- Department of Experimental Medicine, University of Lleida-Lleida Biomedical Research Institute (UdL-IRBLleida), Lleida, Spain
| | - Gustavo Barja
- Department of Genetics, Physiology and Microbiology, Complutense University of Madrid, Madrid, Spain
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7
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Melin F, Hellwig P. Redox Properties of the Membrane Proteins from the Respiratory Chain. Chem Rev 2020; 120:10244-10297. [DOI: 10.1021/acs.chemrev.0c00249] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Frederic Melin
- Chimie de la Matière Complexe UMR 7140, Laboratoire de Bioelectrochimie et Spectroscopie, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France
| | - Petra Hellwig
- Chimie de la Matière Complexe UMR 7140, Laboratoire de Bioelectrochimie et Spectroscopie, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France
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8
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Khaniya U, Gupta C, Cai X, Mao J, Kaur D, Zhang Y, Singharoy A, Gunner MR. Hydrogen bond network analysis reveals the pathway for the proton transfer in the E-channel of T. thermophilus Complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148240. [PMID: 32531220 DOI: 10.1016/j.bbabio.2020.148240] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 05/19/2020] [Accepted: 06/03/2020] [Indexed: 10/24/2022]
Abstract
Complex I, NADH-ubiquinone oxidoreductase, is the first enzyme in the mitochondrial and bacterial aerobic respiratory chain. It pumps four protons through four transiently open pathways from the high pH, negative, N-side of the membrane to the positive, P-side driven by the exergonic transfer of electrons from NADH to a quinone. Three protons transfer through subunits descended from antiporters, while the fourth, E-channel is unique. The path through the E-channel is determined by a network analysis of hydrogen bonded pathways obtained by Monte Carlo sampling of protonation states, polar hydrogen orientation and water occupancy. Input coordinates are derived from molecular dynamics trajectories comparing oxidized, reduced (dihydro) and no menaquinone-8 (MQ). A complex proton transfer path from the N- to the P-side is found consisting of six clusters of highly connected hydrogen-bonded residues. The network connectivity depends on the presence of quinone and its redox state, supporting a role for this cofactor in coupling electron and proton transfers. The N-side is more organized with MQ-bound complex I facilitating proton entry, while the P-side is more connected in the apo-protein, facilitating proton exit. Subunit Nqo8 forms the core of the E channel; Nqo4 provides the N-side entry, Nqo7 and then Nqo10 join the pathway in the middle, while Nqo11 contributes to the P-side exit.
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Affiliation(s)
- Umesh Khaniya
- Department of Physics, City College of New York, New York 10031, USA; Department of Physics, The Graduate Center, City University of New York, New York 10016, USA
| | - Chitrak Gupta
- School of Molecular Sciences, Arizona State University, Tempe, AZ, USA; Biodesign Institute, Arizona State University, Tempe, AZ, USA
| | - Xiuhong Cai
- Department of Physics, City College of New York, New York 10031, USA; Department of Physics, The Graduate Center, City University of New York, New York 10016, USA
| | - Junjun Mao
- Department of Physics, City College of New York, New York 10031, USA
| | - Divya Kaur
- Department of Physics, City College of New York, New York 10031, USA; Department of Chemistry, The Graduate Center, City University of New York, New York 10016, USA
| | - Yingying Zhang
- Department of Physics, City College of New York, New York 10031, USA; Department of Physics, The Graduate Center, City University of New York, New York 10016, USA
| | - Abhishek Singharoy
- School of Molecular Sciences, Arizona State University, Tempe, AZ, USA; Biodesign Institute, Arizona State University, Tempe, AZ, USA
| | - M R Gunner
- Department of Physics, City College of New York, New York 10031, USA; Department of Physics, The Graduate Center, City University of New York, New York 10016, USA; Department of Chemistry, The Graduate Center, City University of New York, New York 10016, USA.
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9
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Gupta C, Khaniya U, Chan CK, Dehez F, Shekhar M, Gunner MR, Sazanov L, Chipot C, Singharoy A. Charge Transfer and Chemo-Mechanical Coupling in Respiratory Complex I. J Am Chem Soc 2020; 142:9220-9230. [PMID: 32347721 DOI: 10.1021/jacs.9b13450] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The mitochondrial respiratory chain, formed by five protein complexes, utilizes energy from catabolic processes to synthesize ATP. Complex I, the first and the largest protein complex of the chain, harvests electrons from NADH to reduce quinone, while pumping protons across the mitochondrial membrane. Detailed knowledge of the working principle of such coupled charge-transfer processes remains, however, fragmentary due to bottlenecks in understanding redox-driven conformational transitions and their interplay with the hydrated proton pathways. Complex I from Thermus thermophilus encases 16 subunits with nine iron-sulfur clusters, reduced by electrons from NADH. Here, employing the latest crystal structure of T. thermophilus complex I, we have used microsecond-scale molecular dynamics simulations to study the chemo-mechanical coupling between redox changes of the iron-sulfur clusters and conformational transitions across complex I. First, we identify the redox switches within complex I, which allosterically couple the dynamics of the quinone binding pocket to the site of NADH reduction. Second, our free-energy calculations reveal that the affinity of the quinone, specifically menaquinone, for the binding-site is higher than that of its reduced, menaquinol form-a design essential for menaquinol release. Remarkably, the barriers to diffusive menaquinone dynamics are lesser than that of the more ubiquitous ubiquinone, and the naphthoquinone headgroup of the former furnishes stronger binding interactions with the pocket, favoring menaquinone for charge transport in T. thermophilus. Our computations are consistent with experimentally validated mutations and hierarchize the key residues into three functional classes, identifying new mutation targets. Third, long-range hydrogen-bond networks connecting the quinone-binding site to the transmembrane subunits are found to be responsible for proton pumping. Put together, the simulations reveal the molecular design principles linking redox reactions to quinone turnover to proton translocation in complex I.
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Affiliation(s)
- Chitrak Gupta
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, United States.,Biodesign Institute, Arizona State University, Tempe, Arizona 85281, United States
| | - Umesh Khaniya
- Department of Physics, City College of New York, New York, New York 10031, United States.,Department of Physics, City University of New York, New York, New York 10017, United States
| | - Chun Kit Chan
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | | | - Mrinal Shekhar
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - M R Gunner
- Department of Physics, City College of New York, New York, New York 10031, United States.,Department of Physics, City University of New York, New York, New York 10017, United States
| | - Leonid Sazanov
- Institute of Science and Technology, 3400 Klosterneuburg, Austria
| | - Christophe Chipot
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,University of Lorraine, Nancy 54000, France
| | - Abhishek Singharoy
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, United States.,Biodesign Institute, Arizona State University, Tempe, Arizona 85281, United States
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10
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Hoias Teixeira M, Menegon Arantes G. Balanced internal hydration discriminates substrate binding to respiratory complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2019; 1860:541-548. [DOI: 10.1016/j.bbabio.2019.05.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 05/16/2019] [Accepted: 05/28/2019] [Indexed: 12/16/2022]
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11
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Hagras MA, Stuchebrukhov AA. Concerted Two-Electron Reduction of Ubiquinone in Respiratory Complex I. J Phys Chem B 2019; 123:5265-5273. [DOI: 10.1021/acs.jpcb.9b04082] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Muhammad A. Hagras
- Department of Chemistry, University of California Davis, One Shields Avenue, Davis, California 95616, United States
| | - Alexei A. Stuchebrukhov
- Department of Chemistry, University of California Davis, One Shields Avenue, Davis, California 95616, United States
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12
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Tran KN, Niu S, Ichiye T. Reduction potential calculations of the Fe–S clusters in
Thermus thermophilus
respiratory complex I. J Comput Chem 2019; 40:1248-1256. [DOI: 10.1002/jcc.25785] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 12/12/2018] [Accepted: 01/06/2019] [Indexed: 01/12/2023]
Affiliation(s)
- Kelly N. Tran
- Department of ChemistryGeorgetown University Washington District of Columbia, 20057
| | - Shuqiang Niu
- Department of ChemistryGeorgetown University Washington District of Columbia, 20057
| | - Toshiko Ichiye
- Department of ChemistryGeorgetown University Washington District of Columbia, 20057
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13
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Manoj KM. Aerobic Respiration: Criticism of the Proton-centric Explanation Involving Rotary Adenosine Triphosphate Synthesis, Chemiosmosis Principle, Proton Pumps and Electron Transport Chain. BIOCHEMISTRY INSIGHTS 2018; 11:1178626418818442. [PMID: 30643418 PMCID: PMC6311555 DOI: 10.1177/1178626418818442] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 11/20/2018] [Indexed: 12/17/2022]
Abstract
The acclaimed explanation for mitochondrial oxidative phosphorylation (mOxPhos, or cellular respiration) is a deterministic proton-centric scheme involving four components: Rotary adenosine triphosphate (ATP)-synthesis, Chemiosmosis principle, Proton pumps, and Electron transport chain (abbreviated as RCPE hypothesis). Within this write-up, the RCPE scheme is critically analyzed with respect to mitochondrial architecture, proteins’ distribution, structure-function correlations and their interactive dynamics, overall reaction chemistry, kinetics, thermodynamics, evolutionary logic, and so on. It is found that the RCPE proposal fails to explain key physiological aspects of mOxPhos in several specific issues and also in holistic perspectives. Therefore, it is imperative to look for new explanations for mOxPhos.
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14
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Schuller JM, Birrell JA, Tanaka H, Konuma T, Wulfhorst H, Cox N, Schuller SK, Thiemann J, Lubitz W, Sétif P, Ikegami T, Engel BD, Kurisu G, Nowaczyk MM. Structural adaptations of photosynthetic complex I enable ferredoxin-dependent electron transfer. Science 2018; 363:257-260. [PMID: 30573545 DOI: 10.1126/science.aau3613] [Citation(s) in RCA: 127] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 12/06/2018] [Indexed: 12/22/2022]
Abstract
Photosynthetic complex I enables cyclic electron flow around photosystem I, a regulatory mechanism for photosynthetic energy conversion. We report a 3.3-angstrom-resolution cryo-electron microscopy structure of photosynthetic complex I from the cyanobacterium Thermosynechococcus elongatus. The model reveals structural adaptations that facilitate binding and electron transfer from the photosynthetic electron carrier ferredoxin. By mimicking cyclic electron flow with isolated components in vitro, we demonstrate that ferredoxin directly mediates electron transfer between photosystem I and complex I, instead of using intermediates such as NADPH (the reduced form of nicotinamide adenine dinucleotide phosphate). A large rate constant for association of ferredoxin to complex I indicates efficient recognition, with the protein subunit NdhS being the key component in this process.
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Affiliation(s)
- Jan M Schuller
- Department of Structural Cell Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
| | - James A Birrell
- Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany
| | - Hideaki Tanaka
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan.,Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan
| | - Tsuyoshi Konuma
- Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Hannes Wulfhorst
- Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany.,Daiichi Sankyo Deutschland GmbH, Zielstattstr. 48, 81379 München, Germany
| | - Nicholas Cox
- Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany.,Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Sandra K Schuller
- Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 Munich, Germany
| | - Jacqueline Thiemann
- Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany
| | - Pierre Sétif
- Institut de Biologie Intégrative de la Cellule (I2BC), IBITECS, CEA, CNRS, Université Paris-Saclay, F-91198 Gif-sur-Yvette, France
| | - Takahisa Ikegami
- Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Benjamin D Engel
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Genji Kurisu
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan. .,Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan
| | - Marc M Nowaczyk
- Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany.
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15
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Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part I. [4Fe-4S] + [2Fe-2S] iron-sulfur proteins. J Struct Biol 2017; 200:1-19. [DOI: 10.1016/j.jsb.2017.05.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 05/25/2017] [Indexed: 01/08/2023]
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16
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Reduction of the off-pathway iron-sulphur cluster N1a of Escherichia coli respiratory complex I restrains NAD + dissociation. Sci Rep 2017; 7:8754. [PMID: 28821859 PMCID: PMC5562879 DOI: 10.1038/s41598-017-09345-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 07/25/2017] [Indexed: 12/24/2022] Open
Abstract
Respiratory complex I couples the electron transfer from NADH to ubiquinone with the translocation of protons across the membrane. The reaction starts with NADH oxidation by a flavin cofactor followed by transferring the electrons through a chain of seven iron-sulphur clusters to quinone. An eighth cluster called N1a is located proximally to flavin, but on the opposite side of the chain of clusters. N1a is strictly conserved although not involved in the direct electron transfer to quinone. Here, we show that the NADH:ferricyanide oxidoreductase activity of E. coli complex I is strongly diminished when the reaction is initiated by an addition of ferricyanide instead of NADH. This effect is significantly less pronounced in a variant containing N1a with a 100 mV more negative redox potential. Detailed kinetic analysis revealed that the reduced activity is due to a lower dissociation constant of bound NAD+. Thus, reduction of N1a induces local structural rearrangements of the protein that stabilise binding of NAD+. The variant features a considerably enhanced production of reactive oxygen species indicating that bound NAD+ represses this process.
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17
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Ježek J, Engstová H, Ježek P. Antioxidant mechanism of mitochondria-targeted plastoquinone SkQ1 is suppressed in aglycemic HepG2 cells dependent on oxidative phosphorylation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:750-762. [PMID: 28554565 DOI: 10.1016/j.bbabio.2017.05.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 05/17/2017] [Accepted: 05/24/2017] [Indexed: 12/19/2022]
Abstract
Previously suggested antioxidant mechanisms for mitochondria-targeted plastoquinone SkQ1 included: i) ion-pairing of cationic SkQ1+ with free fatty acid anions resulting in uncoupling; ii) SkQ1H2 ability to interact with lipoperoxyl radical; iii) interference with electron flow at the inner ubiquinone (Q) binding site of Complex III (Qi), involving the reduction of SkQ1 to SkQ1H2 by ubiquinol. We elucidated SkQ1 antioxidant properties by confocal fluorescence semi-quantification of mitochondrial superoxide (Jm) and cytosolic H2O2 (Jc) release rates in HepG2 cells. Only in glycolytic cells, SkQ1 prevented the rotenone-induced enhancement of Jm and Jc but not basal releases without rotenone. The effect ceased in glutaminolytic aglycemic cells, in which the redox parameter NAD(P)H/FAD increased after rotenone in contrast to its decrease in glycolytic cells. Autofluorescence decay indicated decreased NADPH/NADH ratios with rotenone in both metabolic modes. SkQ1 did not increase cell respiration and diminished Jm established high by antimycin or myxothiazol but not by stigmatellin. The revealed SkQ1 antioxidant modes reflect its reduction to SkQ1H2 at Complex I IQ or Complex III Qi site. Both reductions diminish electron diversions to oxygen thus attenuating superoxide formation. Resulting SkQ1H2 oxidizes back to SkQ1at the second (flavin) Complex I site, previously indicated for MitoQ10. Regeneration proceeds only at lower NAD(P)H/FAD in glycolytic cells. In contrast, cyclic SkQ1 reduction/SkQ1H2 oxidation does not substantiate antioxidant activity in intact cells in the absence of oxidative stress (neither pro-oxidant activity, representing a great advantage). A targeted delivery to oxidative-stressed tissues is suggested for the effective antioxidant therapy based on SkQ1.
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Affiliation(s)
- Jan Ježek
- Department No. 75, Institute of Physiology, Academy of Sciences, Vídeňská 1083, Prague 14220, Czech Republic.
| | - Hana Engstová
- Department No. 75, Institute of Physiology, Academy of Sciences, Vídeňská 1083, Prague 14220, Czech Republic
| | - Petr Ježek
- Department No. 75, Institute of Physiology, Academy of Sciences, Vídeňská 1083, Prague 14220, Czech Republic.
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18
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Fiedorczuk K, Letts JA, Degliesposti G, Kaszuba K, Skehel M, Sazanov LA. Atomic structure of the entire mammalian mitochondrial complex I. Nature 2016; 538:406-410. [PMID: 27595392 DOI: 10.1038/nature19794] [Citation(s) in RCA: 359] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 08/26/2016] [Indexed: 12/15/2022]
Abstract
Mitochondrial complex I (also known as NADH:ubiquinone oxidoreductase) contributes to cellular energy production by transferring electrons from NADH to ubiquinone coupled to proton translocation across the membrane. It is the largest protein assembly of the respiratory chain with a total mass of 970 kilodaltons. Here we present a nearly complete atomic structure of ovine (Ovis aries) mitochondrial complex I at 3.9 Å resolution, solved by cryo-electron microscopy with cross-linking and mass-spectrometry mapping experiments. All 14 conserved core subunits and 31 mitochondria-specific supernumerary subunits are resolved within the L-shaped molecule. The hydrophilic matrix arm comprises flavin mononucleotide and 8 iron-sulfur clusters involved in electron transfer, and the membrane arm contains 78 transmembrane helices, mostly contributed by antiporter-like subunits involved in proton translocation. Supernumerary subunits form an interlinked, stabilizing shell around the conserved core. Tightly bound lipids (including cardiolipins) further stabilize interactions between the hydrophobic subunits. Subunits with possible regulatory roles contain additional cofactors, NADPH and two phosphopantetheine molecules, which are shown to be involved in inter-subunit interactions. We observe two different conformations of the complex, which may be related to the conformationally driven coupling mechanism and to the active-deactive transition of the enzyme. Our structure provides insight into the mechanism, assembly, maturation and dysfunction of mitochondrial complex I, and allows detailed molecular analysis of disease-causing mutations.
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Affiliation(s)
- Karol Fiedorczuk
- Institute of Science and Technology Austria, Klosterneuburg 3400, Austria.,MRC Mitochondrial Biology Unit, Cambridge CB2 0XY, UK
| | - James A Letts
- Institute of Science and Technology Austria, Klosterneuburg 3400, Austria
| | | | - Karol Kaszuba
- Institute of Science and Technology Austria, Klosterneuburg 3400, Austria
| | - Mark Skehel
- MRC Laboratory of Molecular Biology, Cambridge CB2 OQH, UK
| | - Leonid A Sazanov
- Institute of Science and Technology Austria, Klosterneuburg 3400, Austria
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19
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Wright JJ, Salvadori E, Bridges HR, Hirst J, Roessler MM. Small-volume potentiometric titrations: EPR investigations of Fe-S cluster N2 in mitochondrial complex I. J Inorg Biochem 2016; 162:201-206. [DOI: 10.1016/j.jinorgbio.2016.04.025] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 02/19/2016] [Accepted: 04/18/2016] [Indexed: 11/17/2022]
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20
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Holt PJ, Efremov RG, Nakamaru-Ogiso E, Sazanov LA. Reversible FMN dissociation from Escherichia coli respiratory complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1777-1785. [PMID: 27555334 DOI: 10.1016/j.bbabio.2016.08.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 08/04/2016] [Accepted: 08/17/2016] [Indexed: 12/13/2022]
Abstract
Respiratory complex I transfers electrons from NADH to quinone, utilizing the reaction energy to translocate protons across the membrane. It is a key enzyme of the respiratory chain of many prokaryotic and most eukaryotic organisms. The reversible NADH oxidation reaction is facilitated in complex I by non-covalently bound flavin mononucleotide (FMN). Here we report that the catalytic activity of E. coli complex I with artificial electron acceptors potassium ferricyanide (FeCy) and hexaamineruthenium (HAR) is significantly inhibited in the enzyme pre-reduced by NADH. Further, we demonstrate that the inhibition is caused by reversible dissociation of FMN. The binding constant (Kd) for FMN increases from the femto- or picomolar range in oxidized complex I to the nanomolar range in the NADH reduced enzyme, with an FMN dissociation time constant of ~5s. The oxidation state of complex I, rather than that of FMN, proved critical to the dissociation. Such dissociation is not observed with the T. thermophilus enzyme and our analysis suggests that the difference may be due to the unusually high redox potential of Fe-S cluster N1a in E. coli. It is possible that the enzyme attenuates ROS production in vivo by releasing FMN under highly reducing conditions.
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Affiliation(s)
- Peter J Holt
- MRC Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
| | - Rouslan G Efremov
- Structural Biology Research Center, VIB, 1050 Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium
| | - Eiko Nakamaru-Ogiso
- Johnson Research Foundation, Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6059, United States
| | - Leonid A Sazanov
- Institute of Science and Technology Austria, Am Campus 1, A-3400 Klosterneuburg, Austria.
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21
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Gnandt E, Dörner K, Strampraad MFJ, de Vries S, Friedrich T. The multitude of iron-sulfur clusters in respiratory complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1068-1072. [PMID: 26944855 DOI: 10.1016/j.bbabio.2016.02.018] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 02/19/2016] [Accepted: 02/26/2016] [Indexed: 12/13/2022]
Abstract
Respiratory complex I couples the electron transfer from NADH to ubiquinone with the translocation of protons across the membrane. Complex I contains one non-covalently bound flavin mononucleotide and, depending on the species, up to ten iron-sulfur (Fe/S) clusters as cofactors. The reason for the presence of the multitude of Fe/S clusters in complex I remained enigmatic for a long time. The question was partly answered by investigations on the evolution of the complex revealing the stepwise construction of the electron transfer domain from several modules. Extension of the ancestral to the modern electron input domain was associated with the acquisition of several Fe/S-proteins. The X-ray structure of the complex showed that the NADH oxidation-site is connected with the quinone-reduction site by a chain of seven Fe/S-clusters. Fast enzyme kinetics revealed that this chain of Fe/S-clusters is used to regulate electron-tunneling rates within the complex. A possible function of the off-pathway cluster N1a is discussed. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.
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Affiliation(s)
- Emmanuel Gnandt
- Albert-Ludwigs-Universität Freiburg, Institut für Biochemie, Albertstr. 21, 79104 Freiburg i. Br., Germany
| | - Katerina Dörner
- Deutsches Elektronen-Synchrotron DESY, CFEL, Notkestr. 85, Hamburg, Germany
| | - Marc F J Strampraad
- Delft University of Technology, Department of Biotechnology, Julianalaan 67, 2628 BC Delft, The Netherlands
| | - Simon de Vries
- Delft University of Technology, Department of Biotechnology, Julianalaan 67, 2628 BC Delft, The Netherlands
| | - Thorsten Friedrich
- Albert-Ludwigs-Universität Freiburg, Institut für Biochemie, Albertstr. 21, 79104 Freiburg i. Br., Germany.
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22
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Wirth C, Brandt U, Hunte C, Zickermann V. Structure and function of mitochondrial complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:902-14. [PMID: 26921811 DOI: 10.1016/j.bbabio.2016.02.013] [Citation(s) in RCA: 215] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 02/16/2016] [Accepted: 02/17/2016] [Indexed: 12/13/2022]
Abstract
Proton-pumping NADH:ubiquinone oxidoreductase (complex I) is the largest and most complicated enzyme of the respiratory chain. Fourteen central subunits represent the minimal form of complex I and can be assigned to functional modules for NADH oxidation, ubiquinone reduction, and proton pumping. In addition, the mitochondrial enzyme comprises some 30 accessory subunits surrounding the central subunits that are not directly associated with energy conservation. Complex I is known to release deleterious oxygen radicals (ROS) and its dysfunction has been linked to a number of hereditary and degenerative diseases. We here review recent progress in structure determination, and in understanding the role of accessory subunits and functional analysis of mitochondrial complex I. For the central subunits, structures provide insight into the arrangement of functional modules including the substrate binding sites, redox-centers and putative proton channels and pump sites. Only for two of the accessory subunits, detailed structures are available. Nevertheless, many of them could be localized in the overall structure of complex I, but most of these assignments have to be considered tentative. Strikingly, redox reactions and proton pumping machinery are spatially completely separated and the site of reduction for the hydrophobic substrate ubiquinone is found deeply buried in the hydrophilic domain of the complex. The X-ray structure of complex I from Yarrowia lipolytica provides clues supporting the previously proposed two-state stabilization change mechanism, in which ubiquinone redox chemistry induces conformational states and thereby drives proton pumping. The same structural rearrangements may explain the active/deactive transition of complex I implying an integrated mechanistic model for energy conversion and regulation. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt.
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Affiliation(s)
- Christophe Wirth
- Institute for Biochemistry and Molecular Biology, ZBMZ, BIOSS Centre for Biological Signalling Studies, University of Freiburg, Germany
| | - Ulrich Brandt
- Nijmegen Center for Mitochondrial Disorders, Radboud University Medical Center, Nijmegen, The Netherlands; Cluster of Excellence Frankfurt "Macromolecular Complexes, Goethe-University, Germany
| | - Carola Hunte
- Institute for Biochemistry and Molecular Biology, ZBMZ, BIOSS Centre for Biological Signalling Studies, University of Freiburg, Germany.
| | - Volker Zickermann
- Structural Bioenergetics Group, Institute of Biochemistry II, Medical School, Goethe-University, Frankfurt am Main, Germany; Cluster of Excellence Frankfurt "Macromolecular Complexes, Goethe-University, Germany.
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23
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Berrisford JM, Baradaran R, Sazanov LA. Structure of bacterial respiratory complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:892-901. [PMID: 26807915 DOI: 10.1016/j.bbabio.2016.01.012] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 01/18/2016] [Accepted: 01/20/2016] [Indexed: 12/23/2022]
Abstract
Complex I (NADH:ubiquinone oxidoreductase) plays a central role in cellular energy production, coupling electron transfer between NADH and quinone to proton translocation. It is the largest protein assembly of respiratory chains and one of the most elaborate redox membrane proteins known. Bacterial enzyme is about half the size of mitochondrial and thus provides its important "minimal" model. Dysfunction of mitochondrial complex I is implicated in many human neurodegenerative diseases. The L-shaped complex consists of a hydrophilic arm, where electron transfer occurs, and a membrane arm, where proton translocation takes place. We have solved the crystal structures of the hydrophilic domain of complex I from Thermus thermophilus, the membrane domain from Escherichia coli and recently of the intact, entire complex I from T. thermophilus (536 kDa, 16 subunits, 9 iron-sulphur clusters, 64 transmembrane helices). The 95Å long electron transfer pathway through the enzyme proceeds from the primary electron acceptor flavin mononucleotide through seven conserved Fe-S clusters to the unusual elongated quinone-binding site at the interface with the membrane domain. Four putative proton translocation channels are found in the membrane domain, all linked by the central flexible axis containing charged residues. The redox energy of electron transfer is coupled to proton translocation by the as yet undefined mechanism proposed to involve long-range conformational changes. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt.
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Affiliation(s)
| | - Rozbeh Baradaran
- Memorial Sloan-Kettering Cancer Center, 430 E 67th Street, NY 10065, USA
| | - Leonid A Sazanov
- Institute of Science and Technology Austria (IST Austria), Am Campus 1, 3400 Klosterneuburg, Austria.
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24
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Hirst J, Roessler MM. Energy conversion, redox catalysis and generation of reactive oxygen species by respiratory complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1857:872-83. [PMID: 26721206 PMCID: PMC4893023 DOI: 10.1016/j.bbabio.2015.12.009] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 12/15/2015] [Accepted: 12/16/2015] [Indexed: 12/30/2022]
Abstract
Complex I (NADH:ubiquinone oxidoreductase) is critical for respiration in mammalian mitochondria. It oxidizes NADH produced by the Krebs' tricarboxylic acid cycle and β-oxidation of fatty acids, reduces ubiquinone, and transports protons to contribute to the proton-motive force across the inner membrane. Complex I is also a significant contributor to cellular oxidative stress. In complex I, NADH oxidation by a flavin mononucleotide, followed by intramolecular electron transfer along a chain of iron–sulfur clusters, delivers electrons and energy to bound ubiquinone. Either at cluster N2 (the terminal cluster in the chain) or upon the binding/reduction/dissociation of ubiquinone/ubiquinol, energy from the redox process is captured to initiate long-range energy transfer through the complex and drive proton translocation. This review focuses on current knowledge of how the redox reaction and proton transfer are coupled, with particular emphasis on the formation and role of semiquinone intermediates in both energy transduction and reactive oxygen species production. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt. Current knowledge of the redox reactions catalyzed by complex I is reviewed. Possible quinone reduction pathways are presented. The presence and number of semiquinone intermediates are deliberated. The involvement of cluster N2/semiquinones in coupled proton transfer is discussed. Evidence for reactive oxygen species production by semiquinones is examined.
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Affiliation(s)
- Judy Hirst
- Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, United Kingdom.
| | - Maxie M Roessler
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom.
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25
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Breuer M, Rosso KM, Blumberger J, Butt JN. Multi-haem cytochromes in Shewanella oneidensis MR-1: structures, functions and opportunities. J R Soc Interface 2015; 12:20141117. [PMID: 25411412 DOI: 10.1098/rsif.2014.1117] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Multi-haem cytochromes are employed by a range of microorganisms to transport electrons over distances of up to tens of nanometres. Perhaps the most spectacular utilization of these proteins is in the reduction of extracellular solid substrates, including electrodes and insoluble mineral oxides of Fe(III) and Mn(III/IV), by species of Shewanella and Geobacter. However, multi-haem cytochromes are found in numerous and phylogenetically diverse prokaryotes where they participate in electron transfer and redox catalysis that contributes to biogeochemical cycling of N, S and Fe on the global scale. These properties of multi-haem cytochromes have attracted much interest and contributed to advances in bioenergy applications and bioremediation of contaminated soils. Looking forward, there are opportunities to engage multi-haem cytochromes for biological photovoltaic cells, microbial electrosynthesis and developing bespoke molecular devices. As a consequence, it is timely to review our present understanding of these proteins and we do this here with a focus on the multitude of functionally diverse multi-haem cytochromes in Shewanella oneidensis MR-1. We draw on findings from experimental and computational approaches which ideally complement each other in the study of these systems: computational methods can interpret experimentally determined properties in terms of molecular structure to cast light on the relation between structure and function. We show how this synergy has contributed to our understanding of multi-haem cytochromes and can be expected to continue to do so for greater insight into natural processes and their informed exploitation in biotechnologies.
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Affiliation(s)
- Marian Breuer
- Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
| | - Kevin M Rosso
- Pacific Northwest National Laboratory, Richland, WA, USA
| | - Jochen Blumberger
- Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
| | - Julea N Butt
- School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
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26
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Sazanov LA. A giant molecular proton pump: structure and mechanism of respiratory complex I. Nat Rev Mol Cell Biol 2015; 16:375-88. [PMID: 25991374 DOI: 10.1038/nrm3997] [Citation(s) in RCA: 321] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The mitochondrial respiratory chain, also known as the electron transport chain (ETC), is crucial to life, and energy production in the form of ATP is the main mitochondrial function. Three proton-translocating enzymes of the ETC, namely complexes I, III and IV, generate proton motive force, which in turn drives ATP synthase (complex V). The atomic structures and basic mechanisms of most respiratory complexes have previously been established, with the exception of complex I, the largest complex in the ETC. Recently, the crystal structure of the entire complex I was solved using a bacterial enzyme. The structure provided novel insights into the core architecture of the complex, the electron transfer and proton translocation pathways, as well as the mechanism that couples these two processes.
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Affiliation(s)
- Leonid A Sazanov
- Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria
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27
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Real-time optical studies of respiratory Complex I turnover. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1837:1973-1980. [PMID: 25283488 DOI: 10.1016/j.bbabio.2014.09.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 08/28/2014] [Accepted: 09/23/2014] [Indexed: 12/16/2022]
Abstract
Reduction of Complex l (NADH:ubiquinone oxidoreductase l) from Escherichia coli by NADH was investigated optically by means of an ultrafast stopped-flow approach. A locally designed microfluidic stopped-flow apparatus with a low volume (0.21Jl) but a long optical path (10 mm) cuvette allowed measurements in the time range from 270 ).IS to seconds. The data acquisition system collected spectra in the visible range every 50 )JS. Analysis of the obtained time-resolved spectral changes upon the reaction of Complex I with NADH revealed three kinetic components with characteristic times of <270 ).IS, 0.45-0.9 ms and 3-6 ms, reflecting reduction of different FeS clusters and FMN. The rate of the major ( T = 0.45-0.9 ms) component was slower than predicted by electron transfer theory for the reduction of all FeS clusters in the intraprotein redox chain. This delay of the reaction was explained by retention of NAD+ in the catalytic site. The fast optical changes in the time range of 0.27- 1.5 ms were not altered significantly in the presence of 1 0-fold excess of NAD+ over NADH. The data obtained on the NuoF E95Q variant of Complex I shows that the single amino acid replacement in the catalytic site caused a strong decrease of NADH binding and/or the hydride transfer from bound NADH to FMN.
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28
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Wikström M, Sharma V, Kaila VRI, Hosler JP, Hummer G. New Perspectives on Proton Pumping in Cellular Respiration. Chem Rev 2015; 115:2196-221. [DOI: 10.1021/cr500448t] [Citation(s) in RCA: 183] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mårten Wikström
- Institute
of Biotechnology, University of Helsinki, Biocenter 3 (Viikinkaari 1), PB
65, Helsinki 00014, Finland
| | - Vivek Sharma
- Department
of Physics, Tampere University of Technology, Korkeakoulunkatu 3, Tampere 33720, Finland
| | - Ville R. I. Kaila
- Department
Chemie, Technische Universität München, Lichtenbergstraße 4, D-85748 Garching, Germany
| | - Jonathan P. Hosler
- Department
of Biochemistry, University of Mississippi Medical Center, Jackson, Mississippi 39216, United States
| | - Gerhard Hummer
- Department
of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue-Straße
3, 60438 Frankfurt
am Main, Germany
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29
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de Vries S, Dörner K, Strampraad MJF, Friedrich T. Die Elektronentunnelraten im Atmungskettenkomplex I sind auf eine effiziente Energiewandlung abgestimmt. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201410967] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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30
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de Vries S, Dörner K, Strampraad MJF, Friedrich T. Electron tunneling rates in respiratory complex I are tuned for efficient energy conversion. Angew Chem Int Ed Engl 2015; 54:2844-8. [PMID: 25600069 PMCID: PMC4506566 DOI: 10.1002/anie.201410967] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Indexed: 12/13/2022]
Abstract
Respiratory complex I converts the free energy of ubiquinone reduction by NADH into a proton motive force, a redox reaction catalyzed by flavin mononucleotide(FMN) and a chain of seven iron–sulfur centers. Electron transfer rates between the centers were determined by ultrafast freeze-quenching and analysis by EPR and UV/Vis spectroscopy. The complex rapidly oxidizes three NADH molecules. The electron-tunneling rate between the most distant centers in the middle of the chain depends on the redox state of center N2 at the end of the chain, and is sixfold slower when N2 is reduced. The conformational changes that accompany reduction of N2 decrease the electronic coupling of the longest electron-tunneling step. The chain of iron–sulfur centers is not just a simple electron-conducting wire; it regulates the electron-tunneling rate synchronizing it with conformation-mediated proton pumping, enabling efficient energy conversion. Synchronization of rates is a principle means of enhancing the specificity of enzymatic reactions.
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Affiliation(s)
- Simon de Vries
- Department of Biotechnology, Institution Delft University of Technology, Julianalaan 67, 2628 BC, Delft (The Netherlands).
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31
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Lauterbach L, Wang H, Horch M, Gee LB, Yoda Y, Tanaka Y, Zebger I, Lenz O, Cramer SP. Nuclear resonance vibrational spectroscopy reveals the FeS cluster composition and active site vibrational properties of an O 2-tolerant NAD +-reducing [NiFe] hydrogenase. Chem Sci 2015; 6:1055-1060. [PMID: 25678951 PMCID: PMC4321745 DOI: 10.1039/c4sc02982h] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Nuclear resonance vibrational spectroscopy is used to characterize all Fe-containing cofactors in a complex multicofactor enzyme.
Hydrogenases are complex metalloenzymes that catalyze the reversible splitting of molecular hydrogen into protons and electrons essentially without overpotential. The NAD+-reducing soluble hydrogenase (SH) from Ralstonia eutropha is capable of H2 conversion even in the presence of usually toxic dioxygen. The molecular details of the underlying reactions are largely unknown, mainly because of limited knowledge of the structure and function of the various metal cofactors present in the enzyme. Here, all iron-containing cofactors of the SH were investigated by 57Fe specific nuclear resonance vibrational spectroscopy (NRVS). Our data provide experimental evidence for one [2Fe2S] center and four [4Fe4S] clusters, which is consistent with the amino acid sequence composition. Only the [2Fe2S] cluster and one of the four [4Fe4S] clusters were reduced upon incubation of the SH with NADH. This finding explains the discrepancy between the large number of FeS clusters and the small amount of FeS cluster-related signals as detected by electron paramagnetic resonance spectroscopic analysis of several NAD+-reducing hydrogenases. For the first time, Fe–CO and Fe–CN modes derived from the [NiFe] active site could be distinguished by NRVS through selective 13C labeling of the CO ligand. This strategy also revealed the molecular coordinates that dominate the individual Fe–CO modes. The present approach explores the complex vibrational signature of the Fe–S clusters and the hydrogenase active site, thereby showing that NRVS represents a powerful tool for the elucidation of complex biocatalysts containing multiple cofactors.
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Affiliation(s)
- Lars Lauterbach
- Institute of Chemistry, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin, Germany ; Department of Chemistry, University of California, One Shields Ave, Davis CA 95616, USA
| | - Hongxin Wang
- Department of Chemistry, University of California, One Shields Ave, Davis CA 95616, USA ; Physical Biosciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley CA 94720, USA
| | - Marius Horch
- Institute of Chemistry, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin, Germany
| | - Leland B Gee
- Department of Chemistry, University of California, One Shields Ave, Davis CA 95616, USA
| | - Yoshitaka Yoda
- JASRI, SPring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Yoshihito Tanaka
- RIKEN, SPring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Ingo Zebger
- Institute of Chemistry, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin, Germany
| | - Oliver Lenz
- Institute of Chemistry, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin, Germany
| | - Stephen P Cramer
- Department of Chemistry, University of California, One Shields Ave, Davis CA 95616, USA ; Physical Biosciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley CA 94720, USA
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32
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Gutiérrez-Sanz O, Olea D, Pita M, Batista AP, Alonso A, Pereira MM, Vélez M, De Lacey AL. Reconstitution of respiratory complex I on a biomimetic membrane supported on gold electrodes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:9007-9015. [PMID: 24988043 DOI: 10.1021/la501825r] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
For the first time, respiratory complex I has been reconstituted on an electrode preserving its structure and activity. Respiratory complex I is a membrane-bound enzyme that has an essential function in cellular energy production. It couples NADH:quinone oxidoreduction to translocation of ions across the cellular (in prokaryotes) or mitochondrial membranes. Therefore, complex I contributes to the establishment and maintenance of the transmembrane difference of electrochemical potential required for adenosine triphosphate synthesis, transport, and motility. Our new strategy has been applied for reconstituting the bacterial complex I from Rhodothermus marinus onto a biomimetic membrane supported on gold electrodes modified with a thiol self-assembled monolayer (SAM). Atomic force microscopy and faradaic impedance measurements give evidence of the biomimetic construction, whereas electrochemical measurements show its functionality. Both electron transfer and proton translocation by respiratory complex I were monitored, simulating in vivo conditions.
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Affiliation(s)
- Oscar Gutiérrez-Sanz
- Instituto de Catalisis y Petroleoquímica, CSIC, c/Marie Curie 2, L10, 28049 Madrid, Spain
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Sazanov LA. The mechanism of coupling between electron transfer and proton translocation in respiratory complex I. J Bioenerg Biomembr 2014; 46:247-53. [PMID: 24943718 DOI: 10.1007/s10863-014-9554-z] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 06/03/2014] [Indexed: 10/25/2022]
Abstract
NADH-ubiquinone oxidoreductase (complex I) is the first and largest enzyme in the respiratory chain of mitochondria and many bacteria. It couples the transfer of two electrons between NADH and ubiquinone to the translocation of four protons across the membrane. Complex I is an L-shaped assembly formed by the hydrophilic (peripheral) arm, containing all the redox centres performing electron transfer and the membrane arm, containing proton-translocating machinery. Mitochondrial complex I consists of 44 subunits of about 1 MDa in total, whilst the prokaryotic enzyme is simpler and generally consists of 14 conserved "core" subunits. Recently we have determined the first atomic structure of the entire complex I, using the enzyme from Thermus thermophilus (536 kDa, 16 subunits, 9 Fe-S clusters, 64 TM helices). Structure suggests a unique coupling mechanism, with redox energy of electron transfer driving proton translocation via long-range (up to ~200 Å) conformational changes. It resembles a steam engine, with coupling elements (akin to coupling rods) linking parts of this molecular machine.
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Affiliation(s)
- Leonid A Sazanov
- Medical Research Council Mitochondrial Biology Unit, Hills road, Cambridge, CB2 0XY, United Kingdom,
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34
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Bak DW, Elliott SJ. Alternative FeS cluster ligands: tuning redox potentials and chemistry. Curr Opin Chem Biol 2014; 19:50-8. [DOI: 10.1016/j.cbpa.2013.12.015] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 12/13/2013] [Accepted: 12/13/2013] [Indexed: 12/14/2022]
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Investigating the function of [2Fe-2S] cluster N1a, the off-pathway cluster in complex I, by manipulating its reduction potential. Biochem J 2013; 456:139-46. [PMID: 23980528 PMCID: PMC3898324 DOI: 10.1042/bj20130606] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
NADH:quinone oxidoreductase (complex I) couples NADH oxidation and quinone reduction to proton translocation across an energy-transducing membrane. All complexes I contain a flavin to oxidize NADH, seven iron–sulfur clusters to transfer electrons from the flavin to quinone and an eighth cluster (N1a) on the opposite side of the flavin. The role of cluster N1a is unknown, but Escherichia coli complex I has an unusually high-potential cluster N1a and its reduced flavin produces H2O2, not superoxide, suggesting that cluster N1a may affect reactive oxygen species production. In the present study, we combine protein film voltammetry with mutagenesis in overproduced N1a-binding subunits to identify two residues that switch N1a between its high- (E. coli, valine and asparagine) and low- (Bos taurus and Yarrowia lipolytica, proline and methionine) potential forms. The mutations were incorporated into E. coli complex I: cluster N1a could no longer be reduced by NADH, but H2O2 and superoxide production were unaffected. The reverse mutations (that increase the potential by ~0.16 V) were incorporated into Y. lipolytica complex I, but N1a was still not reduced by NADH. We conclude that cluster N1a does not affect reactive oxygen species production by the complex I flavin; it is probably required for enzyme assembly or stability. Two residues that determine the potential of cluster N1a in respiratory complex I were identified, and their effects on its flavin-site reactions were determined. Reduction of cluster N1a by NADH does not affect reactive oxygen species production by the flavin.
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36
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Verkhovskaya M, Wikström M. Oxidoreduction properties of bound ubiquinone in Complex I from Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:246-50. [PMID: 24216024 DOI: 10.1016/j.bbabio.2013.11.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 10/31/2013] [Accepted: 11/04/2013] [Indexed: 12/12/2022]
Abstract
The exploration of the redox chemistry of bound ubiquinone during catalysis is a prerequisite for the understanding of the mechanism by which Complex I (nicotinamide adenine dinucleotide (NADH):ubiquinone oxidoreductase) transduces redox energy into an electrochemical proton gradient. Studies of redox dependent changes in the spectrum of Complex I from Escherichia coli in the mid- and near-ultraviolet (UV) and visible areas were performed to identify the spectral contribution, and to determine the redox properties, of the tightly bound ubiquinone. A very low midpoint redox potential (<-300mV) was found for the bound ubiquinone, more than 400mV lower than when dissolved in a phospholipid membrane. This thermodynamic property of bound ubiquinone has important implications for the mechanism by which Complex I catalyzes proton translocation.
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Affiliation(s)
- Marina Verkhovskaya
- Helsinki Bioenergetics Group, Institute of Biotechnology, University of Helsinki, PO Box 65 (Viikinkaari 1), FIN-00014 Helsinki, Finland.
| | - Mårten Wikström
- Helsinki Bioenergetics Group, Institute of Biotechnology, University of Helsinki, PO Box 65 (Viikinkaari 1), FIN-00014 Helsinki, Finland
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Narayanan M, Gabrieli DJ, Leung SA, Elguindy MM, Glaser CA, Saju N, Sinha SC, Nakamaru-Ogiso E. Semiquinone and cluster N6 signals in His-tagged proton-translocating NADH:ubiquinone oxidoreductase (complex I) from Escherichia coli. J Biol Chem 2013; 288:14310-14319. [PMID: 23543743 DOI: 10.1074/jbc.m113.467803] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
NADH:ubiquinone oxidoreductase (complex I) pumps protons across the membrane using downhill redox energy. The Escherichia coli complex I consists of 13 different subunits named NuoA-N coded by the nuo operon. Due to the low abundance of the protein and some difficulty with the genetic manipulation of its large ~15-kb operon, purification of E. coli complex I has been technically challenging. Here, we generated a new strain in which a polyhistidine sequence was inserted upstream of nuoE in the operon. This allowed us to prepare large amounts of highly pure and active complex I by efficient affinity purification. The purified complex I contained 0.94 ± 0.1 mol of FMN, 29.0 ± 0.37 mol of iron, and 1.99 ± 0.07 mol of ubiquinone/1 mol of complex I. The extinction coefficient of isolated complex I was 495 mM(-1) cm(-1) at 274 nm and 50.3 mM(-1) cm(-1) at 410 nm. NADH:ferricyanide activity was 219 ± 9.7 μmol/min/mg by using HEPES-Bis-Tris propane, pH 7.5. Detailed EPR analyses revealed two additional iron-sulfur cluster signals, N6a and N6b, in addition to previously assigned signals. Furthermore, we found small but significant semiquinone signal(s), which have been reported only for bovine complex I. The line width was ~12 G, indicating its neutral semiquinone form. More than 90% of the semiquinone signal originated from the single entity with P½ (half-saturation power level) = 1.85 milliwatts. The semiquinone signal(s) decreased by 60% when with asimicin, a potent complex I inhibitor. The functional role of semiquinone and the EPR assignment of clusters N6a/N6b are discussed.
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Affiliation(s)
- Madhavan Narayanan
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - David J Gabrieli
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Steven A Leung
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Mahmoud M Elguindy
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Carl A Glaser
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Nitha Saju
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Subhash C Sinha
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Eiko Nakamaru-Ogiso
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
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38
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Abstract
Complex I (NADH:ubiquinone oxidoreductase) is crucial for respiration in many aerobic organisms. In mitochondria, it oxidizes NADH from the tricarboxylic acid cycle and β-oxidation, reduces ubiquinone, and transports protons across the inner membrane, contributing to the proton-motive force. It is also a major contributor to cellular production of reactive oxygen species. The redox reaction of complex I is catalyzed in the hydrophilic domain; it comprises NADH oxidation by a flavin mononucleotide, intramolecular electron transfer along a chain of iron-sulfur clusters, and ubiquinone reduction. Redox-coupled proton translocation in the membrane domain requires long-range energy transfer through the protein complex, and the molecular mechanisms that couple the redox and proton-transfer half-reactions are currently unknown. This review evaluates extant data on the mechanisms of energy transduction and superoxide production by complex I, discusses contemporary mechanistic models, and explores how mechanistic studies may contribute to understanding the roles of complex I dysfunctions in human diseases.
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Affiliation(s)
- Judy Hirst
- Medical Research Council Mitochondrial Biology Unit, Cambridge, CB2 0XY, United Kingdom.
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39
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Verkhovskaya M, Bloch DA. Energy-converting respiratory Complex I: on the way to the molecular mechanism of the proton pump. Int J Biochem Cell Biol 2012; 45:491-511. [PMID: 22982742 DOI: 10.1016/j.biocel.2012.08.024] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 08/27/2012] [Accepted: 08/28/2012] [Indexed: 12/16/2022]
Abstract
In respiring organisms the major energy transduction flux employs the transmembrane electrochemical proton gradient as a physical link between exergonic redox reactions and endergonic ADP phosphorylation. Establishing the gradient involves electrogenic, transmembrane H(+) translocation by the membrane-embedded respiratory complexes. Among others, Complex I (NADH:ubiquinone oxidoreductase) is the most structurally complex and functionally enigmatic respiratory enzyme; its molecular mechanism is as yet unknown. Here we highlight recent progress and discuss the catalytic events during Complex I turnover in relation to their role in energy conversion and to the enzyme structure.
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Affiliation(s)
- Marina Verkhovskaya
- Helsinki Bioenergetics Group, Institute of Biotechnology, PO Box 65 (Viikinkaari 1) FIN-00014 University of Helsinki, Finland.
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