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Padavannil A, Ayala-Hernandez MG, Castellanos-Silva EA, Letts JA. The Mysterious Multitude: Structural Perspective on the Accessory Subunits of Respiratory Complex I. Front Mol Biosci 2022; 8:798353. [PMID: 35047558 PMCID: PMC8762328 DOI: 10.3389/fmolb.2021.798353] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 11/25/2021] [Indexed: 01/10/2023] Open
Abstract
Complex I (CI) is the largest protein complex in the mitochondrial oxidative phosphorylation electron transport chain of the inner mitochondrial membrane and plays a key role in the transport of electrons from reduced substrates to molecular oxygen. CI is composed of 14 core subunits that are conserved across species and an increasing number of accessory subunits from bacteria to mammals. The fact that adding accessory subunits incurs costs of protein production and import suggests that these subunits play important physiological roles. Accordingly, knockout studies have demonstrated that accessory subunits are essential for CI assembly and function. Furthermore, clinical studies have shown that amino acid substitutions in accessory subunits lead to several debilitating and fatal CI deficiencies. Nevertheless, the specific roles of CI’s accessory subunits have remained mysterious. In this review, we explore the possible roles of each of mammalian CI’s 31 accessory subunits by integrating recent high-resolution CI structures with knockout, assembly, and clinical studies. Thus, we develop a framework of experimentally testable hypotheses for the function of the accessory subunits. We believe that this framework will provide inroads towards the complete understanding of mitochondrial CI physiology and help to develop strategies for the treatment of CI deficiencies.
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Affiliation(s)
- Abhilash Padavannil
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, United States
| | - Maria G Ayala-Hernandez
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, United States
| | - Eimy A Castellanos-Silva
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, United States
| | - James A Letts
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, United States
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2
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Rhooms SK, Murari A, Goparaju NSV, Vilanueva M, Owusu-Ansah E. Insights from Drosophila on mitochondrial complex I. Cell Mol Life Sci 2020; 77:607-618. [PMID: 31485716 PMCID: PMC7289077 DOI: 10.1007/s00018-019-03293-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 08/08/2019] [Accepted: 08/28/2019] [Indexed: 12/26/2022]
Abstract
NADH:ubiquinone oxidoreductase, more commonly referred to as mitochondrial complex I (CI), is the largest discrete enzyme of the oxidative phosphorylation system (OXPHOS). It is localized to the mitochondrial inner membrane. CI oxidizes NADH generated from the tricarboxylic acid cycle to NAD+, in a series of redox reactions that culminates in the reduction of ubiquinone, and the transport of protons from the matrix across the inner membrane to the intermembrane space. The resulting proton-motive force is consumed by ATP synthase to generate ATP, or harnessed to transport ions, metabolites and proteins into the mitochondrion. CI is also a major source of reactive oxygen species. Accordingly, impaired CI function has been associated with a host of chronic metabolic and degenerative disorders such as diabetes, cardiomyopathy, Parkinson's disease (PD) and Leigh syndrome. Studies on Drosophila have contributed to our understanding of the multiple roles of CI in bioenergetics and organismal physiology. Here, we explore and discuss some of the studies on Drosophila that have informed our understanding of this complex and conclude with some of the open questions about CI that can be resolved by studies on Drosophila.
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Affiliation(s)
- Shauna-Kay Rhooms
- Department of Physiology and Cellular Biophysics, Columbia University Medical Center, New York, NY, 10032, USA
| | - Anjaneyulu Murari
- Department of Physiology and Cellular Biophysics, Columbia University Medical Center, New York, NY, 10032, USA
| | - Naga Sri Vidya Goparaju
- Department of Physiology and Cellular Biophysics, Columbia University Medical Center, New York, NY, 10032, USA
| | - Maximino Vilanueva
- Department of Physiology and Cellular Biophysics, Columbia University Medical Center, New York, NY, 10032, USA
| | - Edward Owusu-Ansah
- Department of Physiology and Cellular Biophysics, Columbia University Medical Center, New York, NY, 10032, USA.
- The Robert N. Butler Columbia Aging Center, Columbia University Medical Center, New York, NY, 10032, USA.
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3
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Abstract
Single-particle electron cryomicroscopy (cryo-EM) has led to a revolution in structural work on mammalian respiratory complex I. Complex I (mitochondrial NADH:ubiquinone oxidoreductase), a membrane-bound redox-driven proton pump, is one of the largest and most complicated enzymes in the mammalian cell. Rapid progress, following the first 5-Å resolution data on bovine complex I in 2014, has led to a model for mouse complex I at 3.3-Å resolution that contains 96% of the 8,518 residues and to the identification of different particle classes, some of which are assigned to biochemically defined states. Factors that helped improve resolution, including improvements to biochemistry, cryo-EM grid preparation, data collection strategy, and image processing, are discussed. Together with recent structural data from an ancient relative, membrane-bound hydrogenase, cryo-EM on mammalian complex I has provided new insights into the proton-pumping machinery and a foundation for understanding the enzyme's catalytic mechanism.
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Affiliation(s)
- Ahmed-Noor A Agip
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, United Kingdom; , , ,
| | - James N Blaza
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, United Kingdom; , , , .,Current affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, United Kingdom
| | - Justin G Fedor
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, United Kingdom; , , ,
| | - Judy Hirst
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, United Kingdom; , , ,
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4
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Abstract
Mitochondria are the power stations of the eukaryotic cell, using the energy released by the oxidation of glucose and other sugars to produce ATP. Electrons are transferred from NADH, produced in the citric acid cycle in the mitochondrial matrix, to oxygen by a series of large protein complexes in the inner mitochondrial membrane, which create a transmembrane electrochemical gradient by pumping protons across the membrane. The flow of protons back into the matrix via a proton channel in the ATP synthase leads to conformational changes in the nucleotide binding pockets and the formation of ATP. The three proton pumping complexes of the electron transfer chain are NADH-ubiquinone oxidoreductase or complex I, ubiquinone-cytochrome c oxidoreductase or complex III, and cytochrome c oxidase or complex IV. Succinate dehydrogenase or complex II does not pump protons, but contributes reduced ubiquinone. The structures of complex II, III and IV were determined by x-ray crystallography several decades ago, but complex I and ATP synthase have only recently started to reveal their secrets by advances in x-ray crystallography and cryo-electron microscopy. The complexes I, III and IV occur to a certain extent as supercomplexes in the membrane, the so-called respirasomes. Several hypotheses exist about their function. Recent cryo-electron microscopy structures show the architecture of the respirasome with near-atomic detail. ATP synthase occurs as dimers in the inner mitochondrial membrane, which by their curvature are responsible for the folding of the membrane into cristae and thus for the huge increase in available surface that makes mitochondria the efficient energy plants of the eukaryotic cell.
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Affiliation(s)
- Joana S Sousa
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Edoardo D'Imprima
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Janet Vonck
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
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5
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Perrier S, Gauquelin L, Tétreault M, Tran L, Webb N, Srour M, Mitchell J, Brunel-Guitton C, Majewski J, Long V, Keller S, Gambello M, Simons C, Vanderver A, Bernard G. Recessive mutations in NDUFA2
cause mitochondrial leukoencephalopathy. Clin Genet 2017; 93:396-400. [DOI: 10.1111/cge.13126] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 08/07/2017] [Accepted: 08/13/2017] [Indexed: 11/30/2022]
Affiliation(s)
- S. Perrier
- Department of Neurology and Neurosurgery; McGill University; Montreal Canada
| | - L. Gauquelin
- Department of Neurology and Neurosurgery; McGill University; Montreal Canada
- Department of Pediatrics; McGill University; Montreal Canada
| | - M. Tétreault
- Department of Human Genetics; McGill University; Montreal Canada
- McGill University and Genome Quebec Innovation Centre; Montreal Canada
| | - L.T. Tran
- Department of Neurology and Neurosurgery; McGill University; Montreal Canada
- Department of Pediatrics; McGill University; Montreal Canada
- Department of Medical Genetics, Montreal Children's Hospital; McGill University Health Center; Montreal Canada
- Child Health and Human Development Program; Research Institute of the McGill University Health Centre; Montreal Canada
| | - N. Webb
- Department of Human Genetics; McGill University; Montreal Canada
- Division of Medical Genetics, Department of Pediatrics; CHU Sainte-Justine and Université de Montréal; Montreal Canada
- Montreal Neurological Institute; McGill University; Montreal Canada
| | - M. Srour
- Department of Neurology and Neurosurgery; McGill University; Montreal Canada
- Department of Pediatrics; McGill University; Montreal Canada
- Child Health and Human Development Program; Research Institute of the McGill University Health Centre; Montreal Canada
| | - J.J. Mitchell
- Department of Pediatrics; McGill University; Montreal Canada
- Department of Medical Genetics, Montreal Children's Hospital; McGill University Health Center; Montreal Canada
| | - C. Brunel-Guitton
- Division of Medical Genetics, Department of Pediatrics; CHU Sainte-Justine and Université de Montréal; Montreal Canada
| | - J. Majewski
- Department of Human Genetics; McGill University; Montreal Canada
- McGill University and Genome Quebec Innovation Centre; Montreal Canada
| | - V. Long
- Department of Human Genetics, Division of Medical Genetics; Emory University School of Medicine; Atlanta Georgia
| | - S. Keller
- Department of Pediatrics, Division of Pediatric Neurology; Emory University School of Medicine; Atlanta Georgia
| | - M.J. Gambello
- Department of Human Genetics, Division of Medical Genetics; Emory University School of Medicine; Atlanta Georgia
| | - C. Simons
- Institute for Molecular Bioscience; The University of Queensland; St. Lucia Australia
| | - A. Vanderver
- Department of Neurology, Perelman School of Medicine; University of Pennsylvania; Philadelphia Pennsylvania
- Division of Neurology; Children's Hospital of Philadelphia; Philadelphia Pennsylvania
| | - G. Bernard
- Department of Neurology and Neurosurgery; McGill University; Montreal Canada
- Department of Pediatrics; McGill University; Montreal Canada
- Department of Medical Genetics, Montreal Children's Hospital; McGill University Health Center; Montreal Canada
- Child Health and Human Development Program; Research Institute of the McGill University Health Centre; Montreal Canada
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6
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Galkin A, Moncada S. Modulation of the conformational state of mitochondrial complex I as a target for therapeutic intervention. Interface Focus 2017; 7:20160104. [PMID: 28382200 DOI: 10.1098/rsfs.2016.0104] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In recent years, there have been significant advances in our understanding of the functions of mitochondrial complex I other than the generation of energy. These include its role in generation of reactive oxygen species, involvement in the hypoxic tissue response and its possible regulation by nitric oxide (NO) metabolites. In this review, we will focus on the hypoxic conformational change of this mitochondrial enzyme, the so-called active/deactive transition. This conformational change is physiological and relevant to the understanding of certain pathological conditions including, in the cardiovascular system, ischaemia/reperfusion (I/R) damage. We will discuss how complex I can be affected by NO metabolites and will outline some potential mitochondria-targeted therapies in I/R damage.
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Affiliation(s)
- Alexander Galkin
- Feil Family Brain and Mind Research Institute, Weill Cornell Medical College, 401 East 61st Street, 5th floor, New York, NY 10065, USA; Queens University Belfast, School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK
| | - Salvador Moncada
- Manchester Cancer Research Centre , University of Manchester , Wilmslow Road, Manchester M20 4QL , UK
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7
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Margita K, Voinov MA, Smirnov AI. Effect of Solution Ionic Strength on the pK a of the Nitroxide pH EPR Probe 2,2,3,4,5,5-Hexamethylimidazolidin-1-oxyl. Cell Biochem Biophys 2017; 75:185-193. [PMID: 28210984 DOI: 10.1007/s12013-017-0780-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 01/03/2017] [Indexed: 10/20/2022]
Abstract
Spin probe and spin labeling Electron Paramagnetic Resonance methods are indispensable research tools for solving a wide range of bioanalytical problems-from measuring microviscosity and polarity of phase-separated liquids to oxygen concentrations in tissues. One of the emerging uses of spin probes are the studies of proton transfer-related and surface electrostatic phenomena. The latter Electron Paramagnetic Resonance methods rely on molecular probes containing an additional functionality capable of reversible ionization (protonation, in particular) in the immediate proximity to an Electron Paramagnetic Resonance-active reporter group, such as (N-O•) for nitroxides. The consequent formation of protonated and nonprotonated nitroxide species with different magnetic parameters (A iso, g iso) could be readily distinguished by Electron Paramagnetic Resonance. Bioanalytical Electron Paramagnetic Resonance studies employing pH-sensitive paramagnetic probes typically involve determination of the equilibrium constant (pK a) between the protonated and nonprotonated forms of the nitroxide. However, any chemical equilibrium involving charged species, such as ionization of acids and bases, and so the reversible protonation of the nitroxide, is known to be affected by an ionic strength of the solution. Currently, only scarce data for the effect of the solution ionic strength on the experimental pK a's of the ionizable nitroxides can be found in the literature. Here we have carried out a series of Electron Paramagnetic Resonance titration experiments for aqueous solutions of 2,2,3,4,5,5-hexamethylimidazolidin-1-oxyl (HMI) nitroxide known for one of the largest differences in the isotropic nitrogen hyperfine coupling constant A iso between the protonated and nonprotonated forms. Electrolyte concentration was varied over an exceptionally large range (i.e., from 0.05 to 5.0 M) to elucidate the effect of ionic strength on the ionization constant of this pH-sensitive Electron Paramagnetic Resonance probe and the data were compared to the Debye-Hückel limiting law. Effects of the ionic strength on the magnetic parameters of the ionizable nitroxides are also discussed.
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Affiliation(s)
- Kaleigh Margita
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, 27606, NC, USA
| | - Maxim A Voinov
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, 27606, NC, USA
| | - Alex I Smirnov
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, 27606, NC, USA.
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8
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Cryo-EM structure of respiratory complex I reveals a link to mitochondrial sulfur metabolism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1935-1942. [PMID: 27693469 DOI: 10.1016/j.bbabio.2016.09.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 09/22/2016] [Accepted: 09/29/2016] [Indexed: 12/17/2022]
Abstract
Mitochondrial complex I is a 1MDa membrane protein complex with a central role in aerobic energy metabolism. The bioenergetic core functions are executed by 14 central subunits that are conserved from bacteria to man. Despite recent progress in structure determination, our understanding of the function of the ~30 accessory subunits associated with the mitochondrial complex is still limited. We have investigated the structure of complex I from the aerobic yeast Yarrowia lipolytica by cryo-electron microscopy. Our density map at 7.9Å resolution closely matches the 3.6-3.9Å X-ray structure of the Yarrowia lipolytica complex. However, the cryo-EM map indicated an additional subunit on the side of the matrix arm above the membrane surface, pointing away from the membrane arm. The density, which is not present in any previously described complex I structure and occurs in about 20 % of the particles, was identified as the accessory sulfur transferase subunit ST1. The Yarrowia lipolytica complex I preparation is active in generating H2S from the cysteine derivative 3-mercaptopyruvate, catalyzed by ST1. We thus provide evidence for a link between respiratory complex I and mitochondrial sulfur metabolism.
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9
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Letts JA, Fiedorczuk K, Sazanov LA. The architecture of respiratory supercomplexes. Nature 2016; 537:644-648. [PMID: 27654913 DOI: 10.1038/nature19774] [Citation(s) in RCA: 359] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Accepted: 08/18/2016] [Indexed: 02/06/2023]
Abstract
Mitochondrial electron transport chain complexes are organized into supercomplexes responsible for carrying out cellular respiration. Here we present three architectures of mammalian (ovine) supercomplexes determined by cryo-electron microscopy. We identify two distinct arrangements of supercomplex CICIII2CIV (the respirasome)-a major 'tight' form and a minor 'loose' form (resolved at the resolution of 5.8 Å and 6.7 Å, respectively), which may represent different stages in supercomplex assembly or disassembly. We have also determined an architecture of supercomplex CICIII2 at 7.8 Å resolution. All observed density can be attributed to the known 80 subunits of the individual complexes, including 132 transmembrane helices. The individual complexes form tight interactions that vary between the architectures, with complex IV subunit COX7a switching contact from complex III to complex I. The arrangement of active sites within the supercomplex may help control reactive oxygen species production. To our knowledge, these are the first complete architectures of the dominant, physiologically relevant state of the electron transport chain.
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Affiliation(s)
- James A Letts
- Institute of Science and Technology Austria, Klosterneuburg 3400, Austria
| | - Karol Fiedorczuk
- Institute of Science and Technology Austria, Klosterneuburg 3400, Austria.,MRC Mitochondrial Biology Unit, Cambridge CB2 0XY, UK
| | - Leonid A Sazanov
- Institute of Science and Technology Austria, Klosterneuburg 3400, Austria
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10
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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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11
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Zhu J, Vinothkumar KR, Hirst J. Structure of mammalian respiratory complex I. Nature 2016; 536:354-358. [PMID: 27509854 PMCID: PMC5027920 DOI: 10.1038/nature19095] [Citation(s) in RCA: 395] [Impact Index Per Article: 49.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 07/08/2016] [Indexed: 12/17/2022]
Abstract
Complex I (NADH:ubiquinone oxidoreductase), one of the largest membrane-bound enzymes in the cell, powers ATP synthesis in mammalian mitochondria by using the reducing potential of NADH to drive protons across the inner membrane. Mammalian complex I1 contains 45 subunits, comprising 14 core subunits that house the catalytic machinery and are conserved from bacteria to humans, and a mammalian-specific cohort of 31 supernumerary subunits1,2. Knowledge about the structures and functions of the supernumerary subunits is fragmentary. Here, we describe a 4.2 Å resolution single-particle cryoEM structure of complex I from Bos taurus. We locate and model all 45 subunits to provide the entire structure of the mammalian complex. Furthermore, computational sorting of the particles identified different structural classes, related by subtle domain movements, which reveal conformationally-dynamic regions and match biochemical descriptions of the ‘active-to-deactive’ enzyme transition that occurs during hypoxia3,4. Thus, our structures provide a foundation for understanding complex I assembly5 and the effects of mutations that cause clinically-relevant complex I dysfunctions6, insights into the structural and functional roles of the supernumerary subunits, and new information on the mechanism and regulation of catalysis.
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Affiliation(s)
- Jiapeng Zhu
- MRC Mitochondrial Biology Unit, Hills Road, Cambridge CB2 0XY, UK
| | - Kutti R Vinothkumar
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Judy Hirst
- MRC Mitochondrial Biology Unit, Hills Road, Cambridge CB2 0XY, UK
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12
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The origin of the supernumerary subunits and assembly factors of complex I: A treasure trove of pathway evolution. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:971-9. [PMID: 27048931 DOI: 10.1016/j.bbabio.2016.03.027] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/16/2016] [Accepted: 03/18/2016] [Indexed: 11/20/2022]
Abstract
We review and document the evolutionary origin of all complex I assembly factors and nine supernumerary subunits from protein families. Based on experimental data and the conservation of critical residues we identify a spectrum of protein function conservation between the complex I representatives and their non-complex I homologs. This spectrum ranges from proteins that have retained their molecular function but in which the substrate specificity may have changed or have become more specific, like NDUFAF5, to proteins that have lost their original molecular function and critical catalytic residues like NDUFAF6. In between are proteins that have retained their molecular function, which however appears unrelated to complex I, like ACAD9, or proteins in which amino acids of the active site are conserved but for which no enzymatic activity has been reported, like NDUFA10. We interpret complex I evolution against the background of molecular evolution theory. Complex I supernumerary subunits and assembly factors appear to have been recruited from proteins that are mitochondrial and/or that are expressed when complex I is active. Within the evolution of complex I and its assembly there are many cases of neofunctionalization after gene duplication, like ACAD9 and TMEM126B, one case of subfunctionalization: ACPM1 and ACPM2 in Yarrowia lipolytica, and one case in which a complex I protein itself appears to have been the source of a new protein from another complex: NDUFS6 gave rise to cytochrome c oxidase subunit COX4/COX5b. Complex I and its assembly can therewith be regarded as a treasure trove for pathway evolution. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt.
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13
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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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14
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Vinothkumar KR, Zhu J, Hirst J. Architecture of mammalian respiratory complex I. Nature 2014; 515:80-84. [PMID: 25209663 PMCID: PMC4224586 DOI: 10.1038/nature13686] [Citation(s) in RCA: 312] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 07/17/2014] [Indexed: 12/18/2022]
Abstract
Complex I (NADH:ubiquinone oxidoreductase) is essential for oxidative phosphorylation in mammalian mitochondria. It couples electron transfer from NADH to ubiquinone with proton translocation across the energy-transducing inner membrane, providing electrons for respiration and driving ATP synthesis. Mammalian complex I contains 44 different nuclear- and mitochondrial-encoded subunits, with a combined mass of 1 MDa. The 14 conserved 'core' subunits have been structurally defined in the minimal, bacterial complex, but the structures and arrangement of the 30 'supernumerary' subunits are unknown. Here we describe a 5 Å resolution structure of complex I from Bos taurus heart mitochondria, a close relative of the human enzyme, determined by single-particle electron cryo-microscopy. We present the structures of the mammalian core subunits that contain eight iron-sulphur clusters and 60 transmembrane helices, identify 18 supernumerary transmembrane helices, and assign and model 14 supernumerary subunits. Thus, we considerably advance knowledge of the structure of mammalian complex I and the architecture of its supernumerary ensemble around the core domains. Our structure provides insights into the roles of the supernumerary subunits in regulation, assembly and homeostasis, and a basis for understanding the effects of mutations that cause a diverse range of human diseases.
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Affiliation(s)
- Kutti R Vinothkumar
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Jiapeng Zhu
- MRC Mitochondrial Biology Unit, Wellcome Trust / MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Judy Hirst
- MRC Mitochondrial Biology Unit, Wellcome Trust / MRC Building, Hills Road, Cambridge, CB2 0XY, UK
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15
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Duarte M, Tomás AM. The mitochondrial complex I of trypanosomatids--an overview of current knowledge. J Bioenerg Biomembr 2014; 46:299-311. [PMID: 24961227 DOI: 10.1007/s10863-014-9556-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 06/17/2014] [Indexed: 01/23/2023]
Abstract
The contribution of trypanosomatid mitochondrial complex I for energy transduction has long been debated. Herein, we summarize current knowledge on the composition and relevance of this enzyme. Bioinformatic and proteomic analyses allowed the identification of many conserved and trypanosomatid-specific subunits of NADH:ubiquinone oxidoreductase, revealing a multifunctional enzyme capable of performing bioenergetic activities and possibly, also of functioning in fatty acid metabolism. A multimeric structure organized in 5 domains of more than 2 MDa is predicted, in contrast to the 1 MDa described for mammalian complex I. The relevance of mitochondrial complex I within the Trypanosomatidae family is quite diverse with its NADH oxidation activity being dispensable for both procyclic and bloodstream Trypanosoma brucei, whereas in Phytomonas serpens the enzyme is the only respiratory complex able to sustain membrane potential. Aside from complex I, trypanosomatid mitochondria contain a type II NADH dehydrogenase and a NADH-dependent fumarate reductase as alternative electron entry points into the respiratory chain and thus, some trypanosomatids may have bypassed the need for complex I. The involvement of each of these enzymes in the maintenance of the mitochondrial redox balance in trypanosomatids is still an open question and requires further investigation.
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Affiliation(s)
- Margarida Duarte
- IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180, Porto, Portugal,
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16
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Abstract
Mitochondrial respiratory complex I is a product of both the nuclear and mitochondrial genomes. The integration of seven subunits encoded in mitochondrial DNA into the inner membrane, their association with 14 nuclear-encoded membrane subunits, the construction of the extrinsic arm from 23 additional nuclear-encoded proteins, iron-sulfur clusters, and flavin mononucleotide cofactor require the participation of assembly factors. Some are intrinsic to the complex, whereas others participate transiently. The suppression of the expression of the NDUFA11 subunit of complex I disrupted the assembly of the complex, and subcomplexes with masses of 550 and 815 kDa accumulated. Eight of the known extrinsic assembly factors plus a hydrophobic protein, C3orf1, were associated with the subcomplexes. The characteristics of C3orf1, of another assembly factor, TMEM126B, and of NDUFA11 suggest that they all participate in constructing the membrane arm of complex I.
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17
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Abstract
Mitochondrial complex I has a molecular mass of almost 1 MDa and comprises more than 40 polypeptides. Fourteen central subunits harbour the bioenergetic core functions. We are only beginning to understand the significance of the numerous accessory subunits. The present review addresses the role of accessory subunits for assembly, stability and regulation of complex I and for cellular functions not directly associated with redox-linked proton translocation.
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18
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Kensche PR, Duarte I, Huynen MA. A three-dimensional topology of complex I inferred from evolutionary correlations. BMC STRUCTURAL BIOLOGY 2012; 12:19. [PMID: 22857522 PMCID: PMC3436739 DOI: 10.1186/1472-6807-12-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 06/28/2012] [Indexed: 11/22/2022]
Abstract
Background The quaternary structure of eukaryotic NADH:ubiquinone oxidoreductase (complex I), the largest complex of the oxidative phosphorylation, is still mostly unresolved. Furthermore, it is unknown where transiently bound assembly factors interact with complex I. We therefore asked whether the evolution of complex I contains information about its 3D topology and the binding positions of its assembly factors. We approached these questions by correlating the evolutionary rates of eukaryotic complex I subunits using the mirror-tree method and mapping the results into a 3D representation by multidimensional scaling. Results More than 60% of the evolutionary correlation among the conserved seven subunits of the complex I matrix arm can be explained by the physical distance between the subunits. The three-dimensional evolutionary model of the eukaryotic conserved matrix arm has a striking similarity to the matrix arm quaternary structure in the bacterium Thermus thermophilus (rmsd=19 Å) and supports the previous finding that in eukaryotes the N-module is turned relative to the Q-module when compared to bacteria. By contrast, the evolutionary rates contained little information about the structure of the membrane arm. A large evolutionary model of 45 subunits and assembly factors allows to predict subunit positions and interactions (rmsd = 52.6 Å). The model supports an interaction of NDUFAF3, C8orf38 and C2orf56 during the assembly of the proximal matrix arm and the membrane arm. The model further suggests a tight relationship between the assembly factor NUBPL and NDUFA2, which both have been linked to iron-sulfur cluster assembly, as well as between NDUFA12 and its paralog, the assembly factor NDUFAF2. Conclusions The physical distance between subunits of complex I is a major correlate of the rate of protein evolution in the complex I matrix arm and is sufficient to infer parts of the complex’s structure with high accuracy. The resulting evolutionary model predicts the positions of a number of subunits and assembly factors.
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Affiliation(s)
- Philip R Kensche
- Center for Molecular and Biomolecular Informatics/Nijmegen Center for Molecular Life Sciences, Radboud University Medical Center, PO Box 9101, Nijmegen, HB, 6500, The Netherlands.
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19
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Yip CY, Harbour ME, Jayawardena K, Fearnley IM, Sazanov LA. Evolution of respiratory complex I: "supernumerary" subunits are present in the alpha-proteobacterial enzyme. J Biol Chem 2010; 286:5023-33. [PMID: 21115482 DOI: 10.1074/jbc.m110.194993] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Modern α-proteobacteria are thought to be closely related to the ancient symbiont of eukaryotes, an ancestor of mitochondria. Respiratory complex I from α-proteobacteria and mitochondria is well conserved at the level of the 14 "core" subunits, consistent with that notion. Mitochondrial complex I contains the core subunits, present in all species, and up to 31 "supernumerary" subunits, generally thought to have originated only within eukaryotic lineages. However, the full protein composition of an α-proteobacterial complex I has not been established previously. Here, we report the first purification and characterization of complex I from the α-proteobacterium Paracoccus denitrificans. Single particle electron microscopy shows that the complex has a well defined L-shape. Unexpectedly, in addition to the 14 core subunits, the enzyme also contains homologues of three supernumerary mitochondrial subunits as follows: B17.2, AQDQ/18, and 13 kDa (bovine nomenclature). This finding suggests that evolution of complex I via addition of supernumerary or "accessory" subunits started before the original endosymbiotic event that led to the creation of the eukaryotic cell. It also provides further confirmation that α-proteobacteria are the closest extant relatives of mitochondria.
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Affiliation(s)
- Chui-ying Yip
- Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, United Kingdom
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20
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Saraiva J, Siqueira CM, de Paula da Silva CHT, Barreto da Silva V, Tudella VG, Silva R, Andrade e Silva ML, Dorta DJ, Bastos JK, Uyemura SA, de Albuquerque S, Curti C. Cubebin and derivatives as inhibitors of mitochondrial complex I. Proposed interaction with subunit B8. J Enzyme Inhib Med Chem 2009; 24:599-606. [DOI: 10.1080/14756360802318845] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Affiliation(s)
- Juliana Saraiva
- 1Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, CEP 14040-903 Ribeirão Preto, SP, Brazil
| | - Claudia Meirelles Siqueira
- 2Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, CEP 14040-903, Ribeirão Preto, SP, Brazil
| | - Carlos Henrique Tomich de Paula da Silva
- 3Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/nCEP 14040-903, Ribeirão Preto, SP, Brazil
| | - Vinicius Barreto da Silva
- 3Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/nCEP 14040-903, Ribeirão Preto, SP, Brazil
| | - Valeria Gomes Tudella
- 1Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, CEP 14040-903 Ribeirão Preto, SP, Brazil
| | - Rosângela Silva
- 4Núcleo de Pesquisa em Ciências Exatas e Tecnológicas, Universidade de Franca, CEP 14404-600 Franca, SP, Brazil
| | - Marcio Luis Andrade e Silva
- 4Núcleo de Pesquisa em Ciências Exatas e Tecnológicas, Universidade de Franca, CEP 14404-600 Franca, SP, Brazil
| | - Daniel Junqueira Dorta
- 2Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, CEP 14040-903, Ribeirão Preto, SP, Brazil
| | - Jairo Kenupp Bastos
- 3Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/nCEP 14040-903, Ribeirão Preto, SP, Brazil
| | - Sérgio Akira Uyemura
- 1Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, CEP 14040-903 Ribeirão Preto, SP, Brazil
| | - Sergio de Albuquerque
- 1Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, CEP 14040-903 Ribeirão Preto, SP, Brazil
| | - Carlos Curti
- 2Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, CEP 14040-903, Ribeirão Preto, SP, Brazil
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21
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Zickermann V, Kerscher S, Zwicker K, Tocilescu MA, Radermacher M, Brandt U. Architecture of complex I and its implications for electron transfer and proton pumping. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:574-83. [PMID: 19366614 DOI: 10.1016/j.bbabio.2009.01.012] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 01/15/2009] [Accepted: 01/15/2009] [Indexed: 11/27/2022]
Abstract
Proton pumping NADH:ubiquinone oxidoreductase (complex I) is the largest and remains by far the least understood enzyme complex of the respiratory chain. It consists of a peripheral arm harbouring all known redox active prosthetic groups and a membrane arm with a yet unknown number of proton translocation sites. The ubiquinone reduction site close to iron-sulfur cluster N2 at the interface of the 49-kDa and PSST subunits has been mapped by extensive site directed mutagenesis. Independent lines of evidence identified electron transfer events during reduction of ubiquinone to be associated with the potential drop that generates the full driving force for proton translocation with a 4H(+)/2e(-) stoichiometry. Electron microscopic analysis of immuno-labelled native enzyme and of a subcomplex lacking the electron input module indicated a distance of 35-60 A of cluster N2 to the membrane surface. Resolution of the membrane arm into subcomplexes showed that even the distal part harbours subunits that are prime candidates to participate in proton translocation because they are homologous to sodium/proton antiporters and contain conserved charged residues in predicted transmembrane helices. The mechanism of redox linked proton translocation by complex I is largely unknown but has to include steps where energy is transmitted over extremely long distances. In this review we compile the available structural information on complex I and discuss implications for complex I function.
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Affiliation(s)
- Volker Zickermann
- Goethe-Universität, Fachbereich Medizin, Molekulare Bioenergetik, ZBC, Theodor-Stern-Kai 7, Haus 26, D-60590 Frankfurt am Main, Germany
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22
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Hoefs SJG, Dieteren CEJ, Distelmaier F, Janssen RJRJ, Epplen A, Swarts HGP, Forkink M, Rodenburg RJ, Nijtmans LG, Willems PH, Smeitink JAM, van den Heuvel LP. NDUFA2 complex I mutation leads to Leigh disease. Am J Hum Genet 2008; 82:1306-15. [PMID: 18513682 DOI: 10.1016/j.ajhg.2008.05.007] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Revised: 04/29/2008] [Accepted: 05/13/2008] [Indexed: 01/21/2023] Open
Abstract
Mitochondrial isolated complex I deficiency is the most frequently encountered OXPHOS defect. We report a patient with an isolated complex I deficiency expressed in skin fibroblasts as well as muscle tissue. Because the parents were consanguineous, we performed homozygosity mapping to identify homozygous regions containing candidate genes such as NDUFA2 on chromosome 5. Screening of this gene on genomic DNA revealed a mutation that interferes with correct splicing and results in the skipping of exon 2. Exon skipping was confirmed on the mRNA level. The mutation in this accessory subunit causes reduced activity and disturbed assembly of complex I. Furthermore, the mutation is associated with a mitochondrial depolarization. The expression and activity of complex I and the depolarization was (partially) rescued with a baculovirus system expressing the NDUFA2 gene.
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Affiliation(s)
- Saskia J G Hoefs
- Department of Pediatrics, Nijmegen Center for Mitochondrial Disorders, Radboud University Nijmegen Medical Center, Nijmegen 6500 HB, The Netherlands
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23
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Mingatto FE, Dorta DJ, dos Santos AB, Carvalho I, da Silva CHTP, da Silva VB, Uyemura SA, dos Santos AC, Curti C. Dehydromonocrotaline inhibits mitochondrial complex I. A potential mechanism accounting for hepatotoxicity of monocrotaline. Toxicon 2007; 50:724-30. [PMID: 17669457 DOI: 10.1016/j.toxicon.2007.06.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2007] [Revised: 06/05/2007] [Accepted: 06/06/2007] [Indexed: 11/21/2022]
Abstract
Monocrotaline is a pyrrolizidine alkaloid present in plants of the Crotalaria species, which causes cytotoxicity and genotoxicity, including hepatotoxicity in animals and humans. It is metabolized by cytochrome P-450 in the liver to the alkylating agent dehydromonocrotaline. We evaluated the effects of monocrotaline and its metabolite on respiration, membrane potential and ATP levels in isolated rat liver mitochondria, and on respiratory chain complex I NADH oxidase activity in submitochondrial particles. Dehydromonocrotaline, but not the parent compound, showed a concentration-dependent inhibition of glutamate/malate-supported state 3 respiration (respiratory chain complex I), but did not affect succinate-supported respiration (complex II). Only dehydromonocrotaline dissipated mitochondrial membrane potential, depleted ATP, and inhibited complex I NADH oxidase activity (IC50=62.06 microM) through a non-competitive type of inhibition (K(I)=8.1 microM). Therefore, dehydromonocrotaline is an inhibitor of the activity of respiratory chain complex I NADH oxidase, an action potentially accounting for the well-documented monocrotaline's hepatotoxicity to animals and humans. The mechanism probably involves change of the complex I conformation resulting from modification of cysteine thiol groups by the metabolite.
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Affiliation(s)
- Fábio E Mingatto
- Laboratório de Bioquímica, Faculdade de Zootecnia, Universidade Estadual Paulista Júlio de Mesquita Filho, Campus de Dracena, 17900-000 Dracena, SP, Brazil.
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24
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Abstract
NADH:quinone oxidoreductase (complex I) pumps protons across the inner membrane of mitochondria or the plasma membrane of many bacteria. Human complex I is involved in numerous pathological conditions and degenerative processes. With 14 central and up to 32 accessory subunits, complex I is among the largest membrane-bound protein assemblies. The peripheral arm of the L-shaped molecule contains flavine mononucleotide and eight or nine iron-sulfur clusters as redox prosthetic groups. Seven of the iron-sulfur clusters form a linear electron transfer chain between flavine and quinone. In most organisms, the seven most hydrophobic subunits forming the core of the membrane arm are encoded by the mitochondrial genome. Most central subunits have evolved from subunits of different hydrogenases and bacterial Na+/H+ antiporters. This evolutionary origin is reflected in three functional modules of complex I. The coupling mechanism of complex I most likely involves semiquinone intermediates that drive proton pumping through redox-linked conformational changes.
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Affiliation(s)
- Ulrich Brandt
- Universität Frankfurt, Fachbereich Medizin, Zentrum der Biologischen Chemie, D-60590 Frankfurt am Main, Germany.
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25
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Ferguson AD, Labunskyy VM, Fomenko DE, Araç D, Chelliah Y, Amezcua CA, Rizo J, Gladyshev VN, Deisenhofer J. NMR Structures of the Selenoproteins Sep15 and SelM Reveal Redox Activity of a New Thioredoxin-like Family. J Biol Chem 2006; 281:3536-43. [PMID: 16319061 DOI: 10.1074/jbc.m511386200] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Selenium has significant health benefits, including potent cancer prevention activity and roles in immune function and the male reproductive system. Selenium-containing proteins, which incorporate this essential micronutrient as selenocysteine, are proposed to mediate the positive effects of dietary selenium. Presented here are the solution NMR structures of the selenoprotein SelM and an ortholog of the selenoprotein Sep15. These data reveal that Sep15 and SelM are structural homologs that establish a new thioredoxin-like protein family. The location of the active-site redox motifs within the fold together with the observed localized conformational changes after thiol-disulfide exchange and measured redox potential indicate that they have redox activity. In mammals, Sep15 expression is regulated by dietary selenium, and either decreased or increased expression of this selenoprotein alters redox homeostasis. A physiological role for Sep15 and SelM as thiol-disulfide oxidoreductases and their contribution to the quality control pathways of the endoplasmic reticulum are discussed.
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Affiliation(s)
- Andrew D Ferguson
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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