1
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Jarman OD, Hirst J. Membrane-domain mutations in respiratory complex I impede catalysis but do not uncouple proton pumping from ubiquinone reduction. PNAS NEXUS 2022; 1:pgac276. [PMID: 36712358 PMCID: PMC9802314 DOI: 10.1093/pnasnexus/pgac276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 12/01/2022] [Indexed: 12/05/2022]
Abstract
Respiratory complex I [NADH:ubiquinone (UQ) oxidoreductase] captures the free energy released from NADH oxidation and UQ reduction to pump four protons across an energy-transducing membrane and power ATP synthesis. Mechanisms for long-range energy coupling in complex I have been proposed from structural data but not yet evaluated by robust biophysical and biochemical analyses. Here, we use the powerful bacterial model system Paracoccus denitrificans to investigate 14 mutations of key residues in the membrane-domain Nqo13/ND4 subunit, defining the rates and reversibility of catalysis and the number of protons pumped per NADH oxidized. We reveal new insights into the roles of highly conserved charged residues in lateral energy transduction, confirm the purely structural role of the Nqo12/ND5 transverse helix, and evaluate a proposed hydrated channel for proton uptake. Importantly, even when catalysis is compromised the enzyme remains strictly coupled (four protons are pumped per NADH oxidized), providing no evidence for escape cycles that circumvent blocked proton-pumping steps.
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Affiliation(s)
- Owen D Jarman
- The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
| | - Judy Hirst
- The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK
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2
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Cloning and Organelle Expression of Bamboo Mitochondrial Complex I Subunits Nad1, Nad2, Nad4, and Nad5 in the Yeast Saccharomyces cerevisiae. Int J Mol Sci 2022; 23:ijms23074054. [PMID: 35409414 PMCID: PMC8999482 DOI: 10.3390/ijms23074054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 04/02/2022] [Accepted: 04/04/2022] [Indexed: 02/04/2023] Open
Abstract
Mitochondrial respiratory complex I catalyzes electron transfer from NADH to ubiquinone and pumps protons from the matrix into the intermembrane space. In particular, the complex I subunits Nad1, Nad2, Nad4, and Nad5, which are encoded by the nad1, nad2, nad4, and nad5 genes, reside at the mitochondrial inner membrane and possibly function as proton (H+) and ion translocators. To understand the individual functional roles of the Nad1, Nad2, Nad4, and Nad5 subunits in bamboo, each cDNA of these four genes was cloned into the pYES2 vector and expressed in the mitochondria of the yeast Saccharomyces cerevisiae. The mitochondrial targeting peptide mt gene (encoding MT) and the egfp marker gene (encoding enhanced green fluorescent protein, EGFP) were fused at the 5'-terminal and 3'-terminal ends, respectively. The constructed plasmids were then transformed into yeast. RNA transcripts and fusion protein expression were observed in the yeast transformants. Mitochondrial localizations of the MT-Nad1-EGFP, MT-Nad2-EGFP, MT-Nad4-EGFP, and MT-Nad5-EGFP fusion proteins were confirmed by fluorescence microscopy. The ectopically expressed bamboo subunits Nad1, Nad2, Nad4, and Nad5 may function in ion translocation, which was confirmed by growth phenotype assays with the addition of different concentrations of K+, Na+, or H+.
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3
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Jarman OD, Biner O, Wright JJ, Hirst J. Paracoccus denitrificans: a genetically tractable model system for studying respiratory complex I. Sci Rep 2021; 11:10143. [PMID: 33980947 PMCID: PMC8115037 DOI: 10.1038/s41598-021-89575-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 04/27/2021] [Indexed: 02/03/2023] Open
Abstract
Mitochondrial complex I (NADH:ubiquinone oxidoreductase) is a crucial metabolic enzyme that couples the free energy released from NADH oxidation and ubiquinone reduction to the translocation of four protons across the inner mitochondrial membrane, creating the proton motive force for ATP synthesis. The mechanism by which the energy is captured, and the mechanism and pathways of proton pumping, remain elusive despite recent advances in structural knowledge. Progress has been limited by a lack of model systems able to combine functional and structural analyses with targeted mutagenic interrogation throughout the entire complex. Here, we develop and present the α-proteobacterium Paracoccus denitrificans as a suitable bacterial model system for mitochondrial complex I. First, we develop a robust purification protocol to isolate highly active complex I by introducing a His6-tag on the Nqo5 subunit. Then, we optimize the reconstitution of the enzyme into liposomes, demonstrating its proton pumping activity. Finally, we develop a strain of P. denitrificans that is amenable to complex I mutagenesis and create a catalytically inactive variant of the enzyme. Our model provides new opportunities to disentangle the mechanism of complex I by combining mutagenesis in every subunit with established interrogative biophysical measurements on both the soluble and membrane bound enzymes.
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Affiliation(s)
- Owen D. Jarman
- grid.5335.00000000121885934The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY UK
| | - Olivier Biner
- grid.5335.00000000121885934The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY UK
| | - John J. Wright
- grid.5335.00000000121885934The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY UK
| | - Judy Hirst
- grid.5335.00000000121885934The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY UK
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4
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Kaila VRI. Long-range proton-coupled electron transfer in biological energy conversion: towards mechanistic understanding of respiratory complex I. J R Soc Interface 2019; 15:rsif.2017.0916. [PMID: 29643224 PMCID: PMC5938582 DOI: 10.1098/rsif.2017.0916] [Citation(s) in RCA: 97] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 03/13/2018] [Indexed: 12/20/2022] Open
Abstract
Biological energy conversion is driven by efficient enzymes that capture, store and transfer protons and electrons across large distances. Recent advances in structural biology have provided atomic-scale blueprints of these types of remarkable molecular machinery, which together with biochemical, biophysical and computational experiments allow us to derive detailed energy transduction mechanisms for the first time. Here, I present one of the most intricate and least understood types of biological energy conversion machinery, the respiratory complex I, and how its redox-driven proton-pump catalyses charge transfer across approximately 300 Å distances. After discussing the functional elements of complex I, a putative mechanistic model for its action-at-a-distance effect is presented, and functional parallels are drawn to other redox- and light-driven ion pumps.
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Affiliation(s)
- Ville R I Kaila
- Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, Garching, Germany
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5
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A modeling and simulation perspective on the mechanism and function of respiratory complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:510-523. [DOI: 10.1016/j.bbabio.2018.04.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 04/03/2018] [Accepted: 04/10/2018] [Indexed: 12/12/2022]
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6
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Agip ANA, Blaza JN, Bridges HR, Viscomi C, Rawson S, Muench SP, Hirst J. Cryo-EM structures of complex I from mouse heart mitochondria in two biochemically defined states. Nat Struct Mol Biol 2018; 25:548-556. [PMID: 29915388 PMCID: PMC6054875 DOI: 10.1038/s41594-018-0073-1] [Citation(s) in RCA: 163] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 04/26/2018] [Indexed: 02/02/2023]
Abstract
Complex I (NADH:ubiquinone oxidoreductase) uses the reducing potential of NADH to drive protons across the energy-transducing inner membrane and power oxidative phosphorylation in mammalian mitochondria. Recent cryo-EM analyses have produced near-complete models of all 45 subunits in the bovine, ovine and porcine complexes and have identified two states relevant to complex I in ischemia-reperfusion injury. Here, we describe the 3.3-Å structure of complex I from mouse heart mitochondria, a biomedically relevant model system, in the 'active' state. We reveal a nucleotide bound in subunit NDUFA10, a nucleoside kinase homolog, and define mechanistically critical elements in the mammalian enzyme. By comparisons with a 3.9-Å structure of the 'deactive' state and with known bacterial structures, we identify differences in helical geometry in the membrane domain that occur upon activation or that alter the positions of catalytically important charged residues. Our results demonstrate the capability of cryo-EM analyses to challenge and develop mechanistic models for mammalian complex I.
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Affiliation(s)
- Ahmed-Noor A Agip
- The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - James N Blaza
- The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Hannah R Bridges
- The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Carlo Viscomi
- The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Shaun Rawson
- School of Biomedical Sciences, Faculty of Biological Sciences and Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, UK
| | - Stephen P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences and Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, UK
| | - Judy Hirst
- The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK.
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7
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Abstract
Complex I functions as the initial electron acceptor in aerobic respiratory chains of most organisms. This gigantic redox-driven enzyme employs the energy from quinone reduction to pump protons across its complete approximately 200-Å membrane domain, thermodynamically driving synthesis of ATP. Despite recently resolved structures from several species, the molecular mechanism by which complex I catalyzes this long-range proton-coupled electron transfer process, however, still remains unclear. We perform here large-scale classical and quantum molecular simulations to study the function of the proton pump in complex I from Thermus thermophilus The simulations suggest that proton channels are established at symmetry-related locations in four subunits of the membrane domain. The channels open up by formation of quasi one-dimensional water chains that are sensitive to the protonation states of buried residues at structurally conserved broken helix elements. Our combined data provide mechanistic insight into long-range coupling effects and predictions for site-directed mutagenesis experiments.
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8
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Functional Role of MrpA in the MrpABCDEFG Na+/H+ Antiporter Complex from the Archaeon Methanosarcina acetivorans. J Bacteriol 2016; 199:JB.00662-16. [PMID: 27799324 DOI: 10.1128/jb.00662-16] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 10/18/2016] [Indexed: 11/20/2022] Open
Abstract
The multisubunit cation/proton antiporter 3 family, also called Mrp, is widely distributed in all three phylogenetic domains (Eukarya, Bacteria, and Archaea). Investigations have focused on Mrp complexes from the domain Bacteria to the exclusion of Archaea, with a consensus emerging that all seven subunits are required for Na+/H+ antiport activity. The MrpA subunit from the MrpABCDEFG Na+/H+ antiporter complex of the archaeon Methanosarcina acetivorans was produced in antiporter-deficient Escherichia coli strains EP432 and KNabc and biochemically characterized to determine the role of MrpA in the complex. Both strains containing MrpA grew in the presence of up to 500 mM NaCl and pH values up to 11.0 with no added NaCl. Everted vesicles from the strains containing MrpA were able to generate a NADH-dependent pH gradient (ΔpH), which was abated by the addition of monovalent cations. The apparent Km values for Na+ and Li+ were similar and ranged from 31 to 63 mM, whereas activity was too low to determine the apparent Km for K+ Optimum activity was obtained between pH 7.0 and 8.0. Homology molecular modeling identified two half-closed symmetry-related ion translocation channels that are linked, forming a continuous path from the cytoplasm to the periplasm, analogous to the NuoL subunit of complex I. Bioinformatics analyses revealed genes encoding homologs of MrpABCDEFG in metabolically diverse methane-producing species. Overall, the results advance the biochemical, evolutionary, and physiological understanding of Mrp complexes that extends to the domain Archaea IMPORTANCE: The work is the first reported characterization of an Mrp complex from the domain Archaea, specifically methanogens, for which Mrp is important for acetotrophic growth. The results show that the MrpA subunit is essential for antiport activity and, importantly, that not all seven subunits are required, which challenges current dogma for Mrp complexes from the domain Bacteria A mechanism is proposed in which an MrpAD subcomplex catalyzes Na+/H+ antiport independent of an MrpBCEFG subcomplex, although the activity of the former is modulated by the latter. Properties of MrpA strengthen proposals that the Mrp complex is of ancient origin and that subunits were recruited to evolve the ancestral complex I. Finally, bioinformatics analyses indicate that Mrp complexes function in diverse methanogenic pathways.
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9
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Morino M, Ogoda S, Krulwich TA, Ito M. Differences in the phenotypic effects of mutations in homologous MrpA and MrpD subunits of the multi-subunit Mrp-type Na +/H + antiporter. Extremophiles 2016; 21:51-64. [PMID: 27709304 DOI: 10.1007/s00792-016-0877-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 09/24/2016] [Indexed: 10/20/2022]
Abstract
Mrp antiporters are the sole antiporters in the Cation/Proton Antiporter 3 family of transporter databases because of their unusual structural complexity, 6-7 hydrophobic proteins that function as a hetero-oligomeric complex. The two largest and homologous subunits, MrpA and MrpD, are essential for antiport activity and have direct roles in ion transport. They also show striking homology with proton-conducting, membrane-embedded Nuo subunits of respiratory chain complex I of bacteria, e.g., Escherichia coli. MrpA has the closest homology to the complex I NuoL subunit and MrpD has the closest homology to the complex I NuoM and N subunits. Here, introduction of mutations in MrpD, in residues that are also present in MrpA, led to defects in antiport function and/or complex formation. No significant phenotypes were detected in strains with mutations in corresponding residues of MrpA, but site-directed changes in the C-terminal region of MrpA had profound effects, showing that the MrpA C-terminal region has indispensable roles in antiport function. The results are consistent with a divergence in adaptations that support the roles of MrpA and MrpD in secondary antiport, as compared to later adaptations supporting homologs in primary proton pumping by the respiratory chain complex I.
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Affiliation(s)
- Masato Morino
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.,, 573-13 Kamitanui, Tarnaki-cho, Watarai-gun, Mie, 519-0417, Japan
| | - Shinichiro Ogoda
- Faculty of Life Sciences, Graduate School of Life Sciences, Toyo University, Oura-gun, Gunma, 374-0193, Japan
| | - Terry Ann Krulwich
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Masahiro Ito
- Faculty of Life Sciences, Graduate School of Life Sciences, Toyo University, Oura-gun, Gunma, 374-0193, Japan. .,Bio-Nano Electronics Research Center, Toyo University, Kawagoe, Saitama, 350-0815, Japan.
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10
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Tursun A, Zhu S, Vik SB. Probing the proton channels in subunit N of Complex I from Escherichia coli through intra-subunit cross-linking. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1840-1848. [PMID: 27632419 DOI: 10.1016/j.bbabio.2016.09.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 08/19/2016] [Accepted: 09/09/2016] [Indexed: 10/21/2022]
Abstract
Respiratory Complex I appears to have 4 sites for proton translocation, which are coupled to the oxidation of NADH and reduction of coenzyme Q. The proton pathways are thought to be made of offset half-channels that connect to the membrane surfaces, and are connected by a horizontal path through the center of the membrane. In this study of the enzyme from Escherichia coli, subunit N, containing one of the sites, was targeted. Pairs of cysteine residues were introduced into neighboring α-helices along the proposed proton pathways. In an effort to constrain conformational changes that might occur during proton translocation, we attempted to form disulfide bonds or methanethiosulfonate bridges between two engineered cysteine residues. Cysteine modification was inferred by the inability of PEG-maleimide to shift the electrophoretic mobility of subunit N, which will occur upon reaction with free sulfhydryl groups. After the cross-linking treatment, NADH oxidase and NADH-driven proton translocation were measured. Ten different pairs of cysteine residues showed evidence of cross-linking. The most significant loss of enzyme activity was seen for residues near the essential Lys 395. This residue is positioned between the proposed proton half-channel to the periplasm and the horizontal connection through subunit N, and is also near the essential Glu 144 of subunit M. The results suggest important conformational changes in this region for the delivery of protons to the periplasm, or for coupling the actions of subunit N to subunit M.
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Affiliation(s)
- Ablat Tursun
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
| | - Shaotong Zhu
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
| | - Steven B Vik
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA.
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11
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Zhu S, Canales A, Bedair M, Vik SB. Loss of Complex I activity in the Escherichia coli enzyme results from truncating the C-terminus of subunit K, but not from cross-linking it to subunits N or L. J Bioenerg Biomembr 2016; 48:325-33. [PMID: 26931547 DOI: 10.1007/s10863-016-9655-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 02/25/2016] [Indexed: 12/16/2022]
Abstract
Complex I is a multi-subunit enzyme of the respiratory chain with seven core subunits in its membrane arm (A, H, J, K, L, M, and N). In the enzyme from Escherichia coli the C-terminal ten amino acids of subunit K lie along the lateral helix of subunit L, and contribute to a junction of subunits K, L and N on the cytoplasmic surface. Using double cysteine mutagenesis, the cross-linking of subunit K (R99C) to either subunit L (K581C) or subunit N (T292C) was attempted. A partial yield of cross-linked product had no effect on the activity of the enzyme, or on proton translocation, suggesting that the C-terminus of subunit K has no dynamic role in function. To further elucidate the role of subunit K genetic deletions were constructed at the C-terminus. Upon the serial deletion of the last 4 residues of the C-terminus of subunit K, various results were obtained. Deletion of one amino acid had little effect on the activity of Complex I, but deletions of 2 or more amino acids led to total loss of enzyme activity and diminished levels of subunits L, M, and N in preparations of membrane vesicles. Together these results suggest that while the C-terminus of subunit K has no dynamic role in energy transduction by Complex I, it is vital for the correct assembly of the enzyme.
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Affiliation(s)
- Shaotong Zhu
- Department of Biological Sciences, Southern Methodist University, Dallas, TX, 75275-0376, USA.,Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Alejandra Canales
- Department of Biological Sciences, Southern Methodist University, Dallas, TX, 75275-0376, USA.,Department of Biochemistry, University of Wisconsin, Madison, WI, 53706, USA
| | - Mai Bedair
- Department of Biological Sciences, Southern Methodist University, Dallas, TX, 75275-0376, USA.,University of Texas Southwestern Medical School, Dallas, TX, 75390, USA
| | - Steven B Vik
- Department of Biological Sciences, Southern Methodist University, Dallas, TX, 75275-0376, USA.
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12
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Kriegel S, Srour B, Steimle S, Friedrich T, Hellwig P. Involvement of Acidic Amino Acid Residues in Zn2+Binding to Respiratory Complex I. Chembiochem 2015; 16:2080-5. [DOI: 10.1002/cbic.201500273] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Indexed: 12/13/2022]
Affiliation(s)
- Sébastien Kriegel
- Laboratoire de Bioelectrochimie et Spectroscopie; UMR 7140; Chimie de la Matière Complexe; Université de Strasbourg; CNRS; 1 rue Blaise Pascal 67070 Strasbourg France
- Université Paris Diderot; Sorbonne Paris Cité; Laboratoire d'Electrochimie Moléculaire; Unité Mixte de Recherche Université-; CNRS No. 7591; Bâtiment Lavoisier 15 rue Jean de Baïf 75205 Paris Cedex 13 France
| | - Batoul Srour
- Laboratoire de Bioelectrochimie et Spectroscopie; UMR 7140; Chimie de la Matière Complexe; Université de Strasbourg; CNRS; 1 rue Blaise Pascal 67070 Strasbourg France
| | - Stefan Steimle
- Albert-Ludwigs-Universität Freiburg; Institut für Biochemie; Albertstrasse 21 79104 Freiburg Germany
| | - Thorsten Friedrich
- Albert-Ludwigs-Universität Freiburg; Institut für Biochemie; Albertstrasse 21 79104 Freiburg Germany
| | - Petra Hellwig
- Laboratoire de Bioelectrochimie et Spectroscopie; UMR 7140; Chimie de la Matière Complexe; Université de Strasbourg; CNRS; 1 rue Blaise Pascal 67070 Strasbourg France
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13
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Steimle S, Schnick C, Burger EM, Nuber F, Krämer D, Dawitz H, Brander S, Matlosz B, Schäfer J, Maurer K, Glessner U, Friedrich T. Cysteine scanning reveals minor local rearrangements of the horizontal helix of respiratory complex I. Mol Microbiol 2015; 98:151-61. [PMID: 26115017 DOI: 10.1111/mmi.13112] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/25/2015] [Indexed: 12/22/2022]
Abstract
The NADH:ubiquinone oxidoreductase, respiratory complex I, couples electron transfer from NADH to ubiquinone with the translocation of protons across the membrane. The complex consists of a peripheral arm catalyzing the redox reaction and a membrane arm catalyzing proton translocation. The membrane arm is almost completely aligned by a 110 Å unique horizontal helix that is discussed to transmit conformational changes induced by the redox reaction in a piston-like movement to the membrane arm driving proton translocation. Here, we analyzed such a proposed movement by cysteine-scanning of the helix of the Escherichia coli complex I. The accessibility of engineered cysteine residues and the flexibility of individual positions were determined by labeling the preparations with a fluorescent marker and a spin-probe, respectively, in the oxidized and reduced states. The differences in fluorescence labeling and the rotational flexibility of the spin probe between both redox states indicate only slight conformational changes at distinct positions of the helix but not a large movement.
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Affiliation(s)
- Stefan Steimle
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Christian Schnick
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Eva-Maria Burger
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Franziska Nuber
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Dorothée Krämer
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Hannah Dawitz
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Sofia Brander
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Bartlomiej Matlosz
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Jacob Schäfer
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Katharina Maurer
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Udo Glessner
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
| | - Thorsten Friedrich
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg i. Br., Germany
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14
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Zhu S, Vik SB. Constraining the Lateral Helix of Respiratory Complex I by Cross-linking Does Not Impair Enzyme Activity or Proton Translocation. J Biol Chem 2015; 290:20761-20773. [PMID: 26134569 DOI: 10.1074/jbc.m115.660381] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Indexed: 12/19/2022] Open
Abstract
Complex I (NADH:ubiquinone oxidoreductase) is a multisubunit, membrane-bound enzyme of the respiratory chain. The energy from NADH oxidation in the peripheral region of the enzyme is used to drive proton translocation across the membrane. One of the integral membrane subunits, nuoL in Escherichia coli, has an unusual lateral helix of ∼75 residues that lies parallel to the membrane surface and has been proposed to play a mechanical role as a piston during proton translocation (Efremov, R. G., Baradaran, R., and Sazanov, L. A. (2010) Nature 465, 441-445). To test this hypothesis we have introduced 11 pairs of cysteine residues into Complex I; in each pair one is in the lateral helix, and the other is in a nearby region of subunit N, M, or L. The double mutants were treated with Cu(2+) ions or with bi-functional methanethiosulfonate reagents to catalyze cross-link formation in membrane vesicles. The yields of cross-linked products were typically 50-90%, as judged by immunoblotting, but in no case did the activity of Complex I decrease by >10-20%, as indicated by deamino-NADH oxidase activity or rates of proton translocation. In contrast, several pairs of cysteine residues introduced at other interfaces of N:M and M:L subunits led to significant loss of activity, in particular, in the region of residue Glu-144 of subunit M. The results do not support the hypothesis that the lateral helix of subunit L functions like a piston, but rather, they suggest that conformational changes might be transmitted more directly through the functional residues of the proton translocation apparatus.
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Affiliation(s)
- Shaotong Zhu
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275-0376
| | - Steven B Vik
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275-0376.
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15
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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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Respiratory complex I fromEscherichia colidoes not transport Na+in the absence of its NuoL subunit. FEBS Lett 2014; 588:4520-5. [DOI: 10.1016/j.febslet.2014.10.030] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 10/24/2014] [Accepted: 10/27/2014] [Indexed: 12/23/2022]
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Friedrich T. On the mechanism of respiratory complex I. J Bioenerg Biomembr 2014; 46:255-68. [PMID: 25022766 DOI: 10.1007/s10863-014-9566-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 07/03/2014] [Indexed: 02/08/2023]
Abstract
The energy-converting NADH:ubiquinone oxidoreductase, respiratory complex I, couples the transfer of electrons from NADH to ubiquinone with the translocation of protons across the membrane. Electron microscopy and X-ray crystallography revealed the two-part structure of the enzyme complex. A peripheral arm extending into the aqueous phase catalyzes the electron transfer reaction. Accordingly, this arm contains the redox-active cofactors, namely one flavin mononucleotide (FMN) and up to ten iron-sulfur (Fe/S) clusters. A membrane arm embedded in the lipid bilayer catalyzes proton translocation by a yet unknown mechanism. The binding site of the substrate (ubi) quinone is located at the interface of the two arms. The oxidation of one NADH is coupled with the translocation of four protons across the membrane. In this review, the binding of the substrates, the intramolecular electron transfer, the role of individual Fe/S clusters and the mechanism of proton translocation are discussed in the light of recent data obtained from our laboratory.
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Affiliation(s)
- Thorsten Friedrich
- Institut für Biochemie, Albert-Ludwigs-Universität, Albertstr. 21, 79104, Freiburg, Germany,
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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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Virzintiene E, Moparthi VK, Al-Eryani Y, Shumbe L, Górecki K, Hägerhäll C. Structure and function of the C-terminal domain of MrpA in theBacillus subtilisMrp-antiporter complex - The evolutionary progenitor of the long horizontal helix in complex I. FEBS Lett 2013; 587:3341-7. [DOI: 10.1016/j.febslet.2013.08.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 08/22/2013] [Accepted: 08/23/2013] [Indexed: 01/15/2023]
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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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