1
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Kamiyama Y, Parkin D, Takano M. Torque generation mechanism in F o motor of ATP synthase elucidated by free-energy and Coulomb-energy landscapes along the c-ring rotation. Biochem Biophys Res Commun 2023; 651:56-61. [PMID: 36791499 DOI: 10.1016/j.bbrc.2023.01.085] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 01/27/2023] [Indexed: 02/05/2023]
Abstract
Fo portion of ATP synthase is a proton-motive rotary motor. The Coulombic attraction between the conserved acidic residues in the c-ring and the arginine in the a-subunit (aR) was early proposed to drive the c-ring rotation relative to the a-subunit, and has been actually observed in our previous molecular dynamics simulation with full atomistic description of Fo embedded in the membrane. In this study, to quantify the driving force, we conducted the umbrella sampling (US) and obtained the free-energy landscape for the c-ring rotation. We first show that the free-energy gradient toward the ATP-synthesis direction appears in the deprotonated state of cE. Using the sampled snapshots that cover a wide range of the rotational angle, we further analyzed the rotational-angle dependence of the hydration and the protonation states and obtained the Coulomb-energy landscapes with a focus on the cE-aR interaction. The results indicate that both the Coulombic solvation energy of cE and the interaction energy between cE and aR contribute to the torque generation for the c-ring rotation.
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Affiliation(s)
- Yukinari Kamiyama
- Department of Pure and Applied Physics, Graduate School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-Ku, Tokyo, 169-8555, Japan
| | - Dan Parkin
- Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-Ku, Tokyo, 169-8555, Japan
| | - Mitsunori Takano
- Department of Pure and Applied Physics, Graduate School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-Ku, Tokyo, 169-8555, Japan; Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-Ku, Tokyo, 169-8555, Japan.
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2
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Parkin D, Takano M. Coulombic Organization in Membrane-Embedded Rotary Motor of ATP Synthase. J Phys Chem B 2023; 127:1552-1562. [PMID: 36734508 DOI: 10.1021/acs.jpcb.2c07875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The electrochemical potential difference of protons across the membrane is used to synthesize ATP through the proton-motive rotatory motion of the membrane-embedded region of ATP synthase called Fo. In this study, we illuminate the unsolved proton-motive rotary mechanism of Fo on the basis of atomistic simulation with full description of protein, lipid, and water molecules, and highlight the underlying Coulombic design. We first show that a water channel is spontaneously formed at the interfacial region between the rotor (c-ring) and the stator (a-subunit). The observed water channel is a full channel penetrating the membrane, but a Coulomb barrier by a strictly conserved arginine of the a-subunit dominates at the midpoint of the full channel, preventing proton leakage. Our molecular dynamics simulation further demonstrates that the Coulomb attraction between the arginine and the essential glutamic acid of the c-subunit drives the c-ring rotation. We finally illustrate that the charge-state changes of the glutamic acids, enabled by the electrochemical potential difference of proton and the thermal motion, can produce unidirectional rotation of the c-ring.
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Affiliation(s)
- Dan Parkin
- Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-Ku, Tokyo169-8555, Japan
| | - Mitsunori Takano
- Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-Ku, Tokyo169-8555, Japan.,Department of Pure and Applied Physics, Waseda University, 3-8-1 Okubo, Shinjuku-Ku, Tokyo169-8555, Japan
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3
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Frasch WD, Bukhari ZA, Yanagisawa S. F1FO ATP synthase molecular motor mechanisms. Front Microbiol 2022; 13:965620. [PMID: 36081786 PMCID: PMC9447477 DOI: 10.3389/fmicb.2022.965620] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 07/26/2022] [Indexed: 11/13/2022] Open
Abstract
The F-ATP synthase, consisting of F1 and FO motors connected by a central rotor and the stators, is the enzyme responsible for synthesizing the majority of ATP in all organisms. The F1 (αβ)3 ring stator contains three catalytic sites. Single-molecule F1 rotation studies revealed that ATP hydrolysis at each catalytic site (0°) precedes a power-stroke that rotates subunit-γ 120° with angular velocities that vary with rotational position. Catalytic site conformations vary relative to subunit-γ position (βE, empty; βD, ADP bound; βT, ATP-bound). During a power stroke, βE binds ATP (0°–60°) and βD releases ADP (60°–120°). Årrhenius analysis of the power stroke revealed that elastic energy powers rotation via unwinding the γ-subunit coiled-coil. Energy from ATP binding at 34° closes βE upon subunit-γ to drive rotation to 120° and forcing the subunit-γ to exchange its tether from βE to βD, which changes catalytic site conformations. In F1FO, the membrane-bound FO complex contains a ring of c-subunits that is attached to subunit-γ. This c-ring rotates relative to the subunit-a stator in response to transmembrane proton flow driven by a pH gradient, which drives subunit-γ rotation in the opposite direction to force ATP synthesis in F1. Single-molecule studies of F1FO embedded in lipid bilayer nanodisks showed that the c-ring transiently stopped F1-ATPase-driven rotation every 36° (at each c-subunit in the c10-ring of E. coli F1FO) and was able to rotate 11° in the direction of ATP synthesis. Protonation and deprotonation of the conserved carboxyl group on each c-subunit is facilitated by separate groups of subunit-a residues, which were determined to have different pKa’s. Mutations of any of any residue from either group changed both pKa values, which changed the occurrence of the 11° rotation proportionately. This supports a Grotthuss mechanism for proton translocation and indicates that proton translocation occurs during the 11° steps. This is consistent with a mechanism in which each 36° of rotation the c-ring during ATP synthesis involves a proton translocation-dependent 11° rotation of the c-ring, followed by a 25° rotation driven by electrostatic interaction of the negatively charged unprotonated carboxyl group to the positively charged essential arginine in subunit-a.
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4
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Yanagisawa S, Frasch WD. pH-dependent 11° F 1F O ATP synthase sub-steps reveal insight into the F O torque generating mechanism. eLife 2021; 10:70016. [PMID: 34970963 PMCID: PMC8754430 DOI: 10.7554/elife.70016] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 12/27/2021] [Indexed: 12/04/2022] Open
Abstract
Most cellular ATP is made by rotary F1FO ATP synthases using proton translocation-generated clockwise torque on the FO c-ring rotor, while F1-ATP hydrolysis can force counterclockwise rotation and proton pumping. The FO torque-generating mechanism remains elusive even though the FO interface of stator subunit-a, which contains the transmembrane proton half-channels, and the c-ring is known from recent F1FO structures. Here, single-molecule F1FO rotation studies determined that the pKa values of the half-channels differ, show that mutations of residues in these channels change the pKa values of both half-channels, and reveal the ability of FO to undergo single c-subunit rotational stepping. These experiments provide evidence to support the hypothesis that proton translocation through FO operates via a Grotthuss mechanism involving a column of single water molecules in each half-channel linked by proton translocation-dependent c-ring rotation. We also observed pH-dependent 11° ATP synthase-direction sub-steps of the Escherichia coli c10-ring of F1FO against the torque of F1-ATPase-dependent rotation that result from H+ transfer events from FO subunit-a groups with a low pKa to one c-subunit in the c-ring, and from an adjacent c-subunit to stator groups with a high pKa. These results support a mechanism in which alternating proton translocation-dependent 11° and 25° synthase-direction rotational sub-steps of the c10-ring occur to sustain F1FO ATP synthesis.
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Affiliation(s)
- Seiga Yanagisawa
- 1School of Life Sciences, Arizona State University, Tempe, United States
| | - Wayne D Frasch
- School of Life Sciences, Arizona State University, Tempe, United States
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5
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Sobti M, Walshe JL, Wu D, Ishmukhametov R, Zeng YC, Robinson CV, Berry RM, Stewart AG. Cryo-EM structures provide insight into how E. coli F 1F o ATP synthase accommodates symmetry mismatch. Nat Commun 2020; 11:2615. [PMID: 32457314 PMCID: PMC7251095 DOI: 10.1038/s41467-020-16387-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 04/30/2020] [Indexed: 12/19/2022] Open
Abstract
F1Fo ATP synthase functions as a biological rotary generator that makes a major contribution to cellular energy production. It comprises two molecular motors coupled together by a central and a peripheral stalk. Proton flow through the Fo motor generates rotation of the central stalk, inducing conformational changes in the F1 motor that catalyzes ATP production. Here we present nine cryo-EM structures of E. coli ATP synthase to 3.1-3.4 Å resolution, in four discrete rotational sub-states, which provide a comprehensive structural model for this widely studied bacterial molecular machine. We observe torsional flexing of the entire complex and a rotational sub-step of Fo associated with long-range conformational changes that indicates how this flexibility accommodates the mismatch between the 3- and 10-fold symmetries of the F1 and Fo motors. We also identify density likely corresponding to lipid molecules that may contribute to the rotor/stator interaction within the Fo motor.
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Affiliation(s)
- Meghna Sobti
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia.,Faculty of Medicine, St Vincent's Clinical School, UNSW Sydney, Kensington, NSW, 2052, Australia
| | - James L Walshe
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia
| | - Di Wu
- Department of Chemistry, University of Oxford, Oxford, OX1 3QZ, United Kingdom
| | - Robert Ishmukhametov
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU, United Kingdom
| | - Yi C Zeng
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, Oxford, OX1 3QZ, United Kingdom
| | - Richard M Berry
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU, United Kingdom
| | - Alastair G Stewart
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia. .,Faculty of Medicine, St Vincent's Clinical School, UNSW Sydney, Kensington, NSW, 2052, Australia.
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6
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Guo H, Suzuki T, Rubinstein JL. Structure of a bacterial ATP synthase. eLife 2019; 8:43128. [PMID: 30724163 PMCID: PMC6377231 DOI: 10.7554/elife.43128] [Citation(s) in RCA: 97] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 02/02/2019] [Indexed: 01/20/2023] Open
Abstract
ATP synthases produce ATP from ADP and inorganic phosphate with energy from a transmembrane proton motive force. Bacterial ATP synthases have been studied extensively because they are the simplest form of the enzyme and because of the relative ease of genetic manipulation of these complexes. We expressed the Bacillus PS3 ATP synthase in Eschericia coli, purified it, and imaged it by cryo-EM, allowing us to build atomic models of the complex in three rotational states. The position of subunit ε shows how it is able to inhibit ATP hydrolysis while allowing ATP synthesis. The architecture of the membrane region shows how the simple bacterial ATP synthase is able to perform the same core functions as the equivalent, but more complicated, mitochondrial complex. The structures reveal the path of transmembrane proton translocation and provide a model for understanding decades of biochemical analysis interrogating the roles of specific residues in the enzyme.
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Affiliation(s)
- Hui Guo
- The Hospital for Sick Children Research Institute, Toronto, Canada.,Department of Medical Biophysics, The University of Toronto, Toronto, Canada
| | - Toshiharu Suzuki
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan.,Department of Molecular Bioscience, Kyoto-Sangyo University, Kyoto, Japan
| | - John L Rubinstein
- The Hospital for Sick Children Research Institute, Toronto, Canada.,Department of Medical Biophysics, The University of Toronto, Toronto, Canada.,Department of Biochemistry, The University of Toronto, Toronto, Canada
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7
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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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8
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Noji H, Ueno H, McMillan DGG. Catalytic robustness and torque generation of the F 1-ATPase. Biophys Rev 2017; 9:103-118. [PMID: 28424741 PMCID: PMC5380711 DOI: 10.1007/s12551-017-0262-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 03/13/2017] [Indexed: 12/28/2022] Open
Abstract
The F1-ATPase is the catalytic portion of the FoF1 ATP synthase and acts as a rotary molecular motor when it hydrolyzes ATP. Two decades have passed since the single-molecule rotation assay of F1-ATPase was established. Although several fundamental issues remain elusive, basic properties of F-type ATPases as motor proteins have been well characterized, and a large part of the reaction scheme has been revealed by the combination of extensive structural, biochemical, biophysical, and theoretical studies. This review is intended to provide a concise summary of the fundamental features of F1-ATPases, by use of the well-described model F1 from the thermophilic Bacillus PS3 (TF1). In the last part of this review, we focus on the robustness of the rotary catalysis of F1-ATPase to provide a perspective on the re-designing of novel molecular machines.
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Affiliation(s)
- Hiroyuki Noji
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo, 113-8656 Japan
| | - Hiroshi Ueno
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo, 113-8656 Japan
| | - Duncan G. G. McMillan
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo, 113-8656 Japan
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9
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Sobti M, Smits C, Wong AS, Ishmukhametov R, Stock D, Sandin S, Stewart AG. Cryo-EM structures of the autoinhibited E. coli ATP synthase in three rotational states. eLife 2016; 5. [PMID: 28001127 PMCID: PMC5214741 DOI: 10.7554/elife.21598] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 12/15/2016] [Indexed: 12/28/2022] Open
Abstract
A molecular model that provides a framework for interpreting the wealth of functional information obtained on the E. coli F-ATP synthase has been generated using cryo-electron microscopy. Three different states that relate to rotation of the enzyme were observed, with the central stalk’s ε subunit in an extended autoinhibitory conformation in all three states. The Fo motor comprises of seven transmembrane helices and a decameric c-ring and invaginations on either side of the membrane indicate the entry and exit channels for protons. The proton translocating subunit contains near parallel helices inclined by ~30° to the membrane, a feature now synonymous with rotary ATPases. For the first time in this rotary ATPase subtype, the peripheral stalk is resolved over its entire length of the complex, revealing the F1 attachment points and a coiled-coil that bifurcates toward the membrane with its helices separating to embrace subunit a from two sides. DOI:http://dx.doi.org/10.7554/eLife.21598.001 ATP synthase is a biological motor that produces a molecule called adenosine tri-phosphate (ATP for short), which acts as the major store of chemical energy in cells. A single molecule of ATP contains three phosphate groups: the cell can remove one of these phosphates to make a molecule called adenosine di-phosphate (ADP) and release energy to drive a variety of biological processes. ATP synthase sits in the membranes that separate cell compartments or form barriers around cells. When cells break down food they transport hydrogen ions across these membranes so that each side of the membrane has a different level (or “concentration”) of hydrogen ions. Movement of hydrogen ions from an area with a high concentration to a low concentration causes ATP synthase to rotate like a turbine. This rotation of the enzyme results in ATP synthase adding a phosphate group to ADP to make a new molecule of ATP. In certain conditions cells need to switch off the ATP synthase and this is done by changing the shape of the central shaft in a process called autoinhibition, which blocks the rotation. The ATP synthase from a bacterium known as E. coli – which is commonly found in the human gut –has been used as a model to study how this biological motor works. However, since the precise details of the three-dimensional structure of ATP synthase have remained unclear it has been difficult to interpret the results of these studies. Sobti et al. used a technique called Cryo-electron microscopy to investigate the structure of ATP synthase from E. coli. This made it possible to develop a three-dimensional model of the ATP synthase in its autoinhibited form. The structural data could also be split into three distinct shapes that relate to dwell points in the rotation of the motor where the rotation has been inhibited. These models further our understanding of ATP synthases and provide a template to understand the findings of previous studies. Further work will be needed to understand this essential biological process at the atomic level in both its inhibited and uninhibited form. This will reveal the inner workings of a marvel of the natural world and may also lead to the discovery of new antibiotics against related bacteria that cause diseases in humans. DOI:http://dx.doi.org/10.7554/eLife.21598.002
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Affiliation(s)
- Meghna Sobti
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Callum Smits
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Andrew Sw Wong
- NTU Institute of Structural Biology, Nanyang Technological University, Singapore, Singapore
| | - Robert Ishmukhametov
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, United Kingdom
| | - Daniela Stock
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, Australia.,Faculty of Medicine, The University of New South Wales, Sydney, Australia
| | - Sara Sandin
- NTU Institute of Structural Biology, Nanyang Technological University, Singapore, Singapore.,School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Alastair G Stewart
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, Australia.,Faculty of Medicine, The University of New South Wales, Sydney, Australia
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10
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Models for the a subunits of the Thermus thermophilus V/A-ATPase and Saccharomyces cerevisiae V-ATPase enzymes by cryo-EM and evolutionary covariance. Proc Natl Acad Sci U S A 2016; 113:3245-50. [PMID: 26951669 DOI: 10.1073/pnas.1521990113] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Rotary ATPases couple ATP synthesis or hydrolysis to proton translocation across a membrane. However, understanding proton translocation has been hampered by a lack of structural information for the membrane-embedded a subunit. The V/A-ATPase from the eubacterium Thermus thermophilus is similar in structure to the eukaryotic V-ATPase but has a simpler subunit composition and functions in vivo to synthesize ATP rather than pump protons. We determined the T. thermophilus V/A-ATPase structure by cryo-EM at 6.4 Å resolution. Evolutionary covariance analysis allowed tracing of the a subunit sequence within the map, providing a complete model of the rotary ATPase. Comparing the membrane-embedded regions of the T. thermophilus V/A-ATPase and eukaryotic V-ATPase from Saccharomyces cerevisiae allowed identification of the α-helices that belong to the a subunit and revealed the existence of previously unknown subunits in the eukaryotic enzyme. Subsequent evolutionary covariance analysis enabled construction of a model of the a subunit in the S. cerevisae V-ATPase that explains numerous biochemical studies of that enzyme. Comparing the two a subunit structures determined here with a structure of the distantly related a subunit from the bovine F-type ATP synthase revealed a conserved pattern of residues, suggesting a common mechanism for proton transport in all rotary ATPases.
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11
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Kühlbrandt W, Davies KM. Rotary ATPases: A New Twist to an Ancient Machine. Trends Biochem Sci 2015; 41:106-116. [PMID: 26671611 DOI: 10.1016/j.tibs.2015.10.006] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 10/14/2015] [Accepted: 10/16/2015] [Indexed: 01/15/2023]
Abstract
Rotary ATPases are energy-converting nanomachines found in the membranes of all living organisms. The mechanism by which proton translocation through the membrane drives ATP synthesis, or how ATP hydrolysis generates a transmembrane proton gradient, has been unresolved for decades because the structure of a critical subunit in the membrane was unknown. Electron cryomicroscopy (cryoEM) studies of two rotary ATPases have now revealed a hairpin of long, horizontal, membrane-intrinsic α-helices in the a-subunit next to the c-ring rotor. The horizontal helices create a pair of aqueous half-channels in the membrane that provide access to the proton-binding sites in the rotor ring. These recent findings help to explain the highly conserved mechanism of ion translocation by rotary ATPases.
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Affiliation(s)
- Werner Kühlbrandt
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue Strasse 3, 60438 Frankfurt am Main, Germany.
| | - Karen M Davies
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue Strasse 3, 60438 Frankfurt am Main, Germany
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12
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Abstract
The F1F0-ATP synthase (EC 3.6.1.34) is a remarkable enzyme that functions as a rotary motor. It is found in the inner membranes of Escherichia coli and is responsible for the synthesis of ATP in response to an electrochemical proton gradient. Under some conditions, the enzyme functions reversibly and uses the energy of ATP hydrolysis to generate the gradient. The ATP synthase is composed of eight different polypeptide subunits in a stoichiometry of α3β3γδεab2c10. Traditionally they were divided into two physically separable units: an F1 that catalyzes ATP hydrolysis (α3β3γδε) and a membrane-bound F0 sector that transports protons (ab2c10). In terms of rotary function, the subunits can be divided into rotor subunits (γεc10) and stator subunits (α3β3δab2). The stator subunits include six nucleotide binding sites, three catalytic and three noncatalytic, formed primarily by the β and α subunits, respectively. The stator also includes a peripheral stalk composed of δ and b subunits, and part of the proton channel in subunit a. Among the rotor subunits, the c subunits form a ring in the membrane, and interact with subunit a to form the proton channel. Subunits γ and ε bind to the c-ring subunits, and also communicate with the catalytic sites through interactions with α and β subunits. The eight subunits are expressed from a single operon, and posttranscriptional processing and translational regulation ensure that the polypeptides are made at the proper stoichiometry. Recent studies, including those of other species, have elucidated many structural and rotary properties of this enzyme.
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13
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Horizontal membrane-intrinsic α-helices in the stator a-subunit of an F-type ATP synthase. Nature 2015; 521:237-40. [PMID: 25707805 DOI: 10.1038/nature14185] [Citation(s) in RCA: 200] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 12/29/2014] [Indexed: 12/12/2022]
Abstract
ATP, the universal energy currency of cells, is produced by F-type ATP synthases, which are ancient, membrane-bound nanomachines. F-type ATP synthases use the energy of a transmembrane electrochemical gradient to generate ATP by rotary catalysis. Protons moving across the membrane drive a rotor ring composed of 8-15 c-subunits. A central stalk transmits the rotation of the c-ring to the catalytic F1 head, where a series of conformational changes results in ATP synthesis. A key unresolved question in this fundamental process is how protons pass through the membrane to drive ATP production. Mitochondrial ATP synthases form V-shaped homodimers in cristae membranes. Here we report the structure of a native and active mitochondrial ATP synthase dimer, determined by single-particle electron cryomicroscopy at 6.2 Å resolution. Our structure shows four long, horizontal membrane-intrinsic α-helices in the a-subunit, arranged in two hairpins at an angle of approximately 70° relative to the c-ring helices. It has been proposed that a strictly conserved membrane-embedded arginine in the a-subunit couples proton translocation to c-ring rotation. A fit of the conserved carboxy-terminal a-subunit sequence places the conserved arginine next to a proton-binding c-subunit glutamate. The map shows a slanting solvent-accessible channel that extends from the mitochondrial matrix to the conserved arginine. Another hydrophilic cavity on the lumenal membrane surface defines a direct route for the protons to an essential histidine-glutamate pair. Our results provide unique new insights into the structure and function of rotary ATP synthases and explain how ATP production is coupled to proton translocation.
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14
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Matthies D, Zhou W, Klyszejko AL, Anselmi C, Yildiz Ö, Brandt K, Müller V, Faraldo-Gómez JD, Meier T. High-resolution structure and mechanism of an F/V-hybrid rotor ring in a Na⁺-coupled ATP synthase. Nat Commun 2014; 5:5286. [PMID: 25381992 PMCID: PMC4228694 DOI: 10.1038/ncomms6286] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 09/16/2014] [Indexed: 01/03/2023] Open
Abstract
All rotary ATPases catalyse the interconversion of ATP and ADP-Pi through a mechanism that is coupled to the transmembrane flow of H(+) or Na(+). Physiologically, however, F/A-type enzymes specialize in ATP synthesis driven by downhill ion diffusion, while eukaryotic V-type ATPases function as ion pumps. To begin to rationalize the molecular basis for this functional differentiation, we solved the crystal structure of the Na(+)-driven membrane rotor of the Acetobacterium woodii ATP synthase, at 2.1 Å resolution. Unlike known structures, this rotor ring is a 9:1 heteromer of F- and V-type c-subunits and therefore features a hybrid configuration of ion-binding sites along its circumference. Molecular and kinetic simulations are used to dissect the mechanisms of Na(+) recognition and rotation of this c-ring, and to explain the functional implications of the V-type c-subunit. These structural and mechanistic insights indicate an evolutionary path between synthases and pumps involving adaptations in the rotor ring.
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Affiliation(s)
- Doreen Matthies
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany
| | - Wenchang Zhou
- Theoretical Molecular Biophysics Section, National Heart, Lung and Blood Institute, National Institutes of Health, Building 5635FL, Suite T-800, Bethesda, Maryland 20892, USA
| | - Adriana L Klyszejko
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany
| | - Claudio Anselmi
- Theoretical Molecular Biophysics Section, National Heart, Lung and Blood Institute, National Institutes of Health, Building 5635FL, Suite T-800, Bethesda, Maryland 20892, USA
| | - Özkan Yildiz
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany
| | - Karsten Brandt
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt am Main, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
| | - Volker Müller
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt am Main, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
| | - José D Faraldo-Gómez
- 1] Theoretical Molecular Biophysics Section, National Heart, Lung and Blood Institute, National Institutes of Health, Building 5635FL, Suite T-800, Bethesda, Maryland 20892, USA [2] Cluster of Excellence Macromolecular Complexes, Max-von-Laue-Str. 15, 60438 Frankfurt am Main, Germany
| | - Thomas Meier
- 1] Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany [2] Cluster of Excellence Macromolecular Complexes, Max-von-Laue-Str. 15, 60438 Frankfurt am Main, Germany
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15
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Fillingame RH, Steed PR. Half channels mediating H+ transport and the mechanism of gating in the Fo sector of Escherichia coli F1Fo ATP synthase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1063-8. [DOI: 10.1016/j.bbabio.2014.03.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 03/06/2014] [Accepted: 03/10/2014] [Indexed: 11/29/2022]
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16
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Abstract
Thyroid hormone (TH) has long been recognized as a major modulator of metabolic efficiency, energy expenditure, and thermogenesis. TH effects in regulating metabolic efficiency are transduced by controlling the coupling of mitochondrial oxidative phosphorylation and the cycling of extramitochondrial substrate/futile cycles. However, despite our present understanding of the genomic and nongenomic modes of action of TH, its control of mitochondrial coupling still remains elusive. This review summarizes historical and up-to-date findings concerned with TH regulation of metabolic energetics, while integrating its genomic and mitochondrial activities. It underscores the role played by TH-induced gating of the mitochondrial permeability transition pore (PTP) in controlling metabolic efficiency. PTP gating may offer a unified target for some TH pleiotropic activities and may serve as a novel target for synthetic functional thyromimetics designed to modulate metabolic efficiency. PTP gating by long-chain fatty acid analogs may serve as a model for such strategy.
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Affiliation(s)
- Einav Yehuda-Shnaidman
- Human Nutrition and Metabolism, Hebrew University Medical School, Jerusalem, Israel 91120
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17
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Gajadeera CS, Weber J. Escherichia coli F1Fo-ATP synthase with a b/δ fusion protein allows analysis of the function of the individual b subunits. J Biol Chem 2013; 288:26441-7. [PMID: 23893411 DOI: 10.1074/jbc.m113.503722] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The "stator stalk" of F1Fo-ATP synthase is essential for rotational catalysis as it connects the nonrotating portions of the enzyme. In Escherichia coli, the stator stalk consists of two (identical) b subunits and the δ subunit. In mycobacteria, one of the b subunits and the δ subunit are replaced by a b/δ fusion protein; the remaining b subunit is of the shorter b' type. In the present study, it is shown that it is possible to generate a functional E. coli ATP synthase containing a b/δ fusion protein. This construct allowed the analysis of the roles of the individual b subunits. The full-length b subunit (which in this case is covalently linked to δ in the fusion protein) is responsible for connecting the stalk to the catalytic F1 subcomplex. It is not required for interaction with the membrane-embedded Fo subcomplex, as its transmembrane helix can be removed. Attachment to Fo is the function of the other b subunit which in turn has only a minor (if any at all) role in binding to δ. Also in E. coli the second b subunit can be shortened to a b' type.
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Affiliation(s)
- Chathurada S Gajadeera
- From the Department of Chemistry and Biochemistry and the Center for Chemical Biology, Texas Tech University, Lubbock, Texas 79409 and the Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430
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18
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Moore KJ, Fillingame RH. Obstruction of transmembrane helical movements in subunit a blocks proton pumping by F1Fo ATP synthase. J Biol Chem 2013; 288:25535-25541. [PMID: 23864659 DOI: 10.1074/jbc.m113.496794] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Subunit a plays a key role in promoting H(+) transport-coupled rotary motion of the subunit c ring in F1Fo ATP synthase. H(+) binding and release occur at Asp-61 in the middle of the second transmembrane helix (TMH) of Fo subunit c. H(+) are thought to reach cAsp61 via aqueous half-channels formed by TMHs 2-5 of subunit a. Movements of TMH4 and TMH5 have been proposed to facilitate protonation of cAsp61 from a half channel centered in a four helix bundle at the periplasmic side of subunit a. The possible necessity of these proposed TMH movements was investigated by assaying ATP driven H(+) pumping function before and after cross-linking paired Cys substitutions at the center of TMHs within subunit a. The cross-linking of the Cys pairs aG218C/I248C in TMH4 and TMH5, and aL120C/H245C in TMH2 and TMH5, inhibited H(+) pumping by 85-90%. H(+) pumping function was largely unaffected by modification of the same Cys residues in the absence of cross-link formation. The inhibition is consistent with the proposed requirement for TMH movements during the gating of periplasmic H(+) access to cAsp61. The cytoplasmic loops of subunit a have been implicated in gating H(+) release to the cytoplasm, and previous cross-linking experiments suggest that the chemically reactive regions of the loops may pack as a single domain. Here we show that Cys substitutions in these domains can be cross-linked with retention of function and conclude that these domains need not undergo large conformational changes during enzyme function.
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Affiliation(s)
- Kyle J Moore
- From the Department of Biomolecular Chemistry, School of Medicine, and Public Health, University of Wisconsin, Madison, Wisconsin 53706
| | - Robert H Fillingame
- From the Department of Biomolecular Chemistry, School of Medicine, and Public Health, University of Wisconsin, Madison, Wisconsin 53706.
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19
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Gohlke H, Schlieper D, Groth G. Resolving the negative potential side (n-side) water-accessible proton pathway of F-type ATP synthase by molecular dynamics simulations. J Biol Chem 2012; 287:36536-43. [PMID: 22942277 DOI: 10.1074/jbc.m112.398396] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The rotation of F(1)F(o)-ATP synthase is powered by the proton motive force across the energy-transducing membrane. The protein complex functions like a turbine; the proton flow drives the rotation of the c-ring of the transmembrane F(o) domain, which is coupled to the ATP-producing F(1) domain. The hairpin-structured c-protomers transport the protons by reversible protonation/deprotonation of a conserved Asp/Glu at the outer transmembrane helix (TMH). An open question is the proton transfer pathway through the membrane at atomic resolution. The protons are thought to be transferred via two half-channels to and from the conserved cAsp/Glu in the middle of the membrane. By molecular dynamics simulations of c-ring structures in a lipid bilayer, we mapped a water channel as one of the half-channels. We also analyzed the suppressor mutant cP24D/E61G in which the functional carboxylate is shifted to the inner TMH of the c-protomers. Current models concentrating on the "locked" and "open" conformations of the conserved carboxylate side chain are unable to explain the molecular function of this mutant. Our molecular dynamics simulations revealed an extended water channel with additional water molecules bridging the distance of the outer to the inner TMH. We suggest that the geometry of the water channel is an important feature for the molecular function of the membrane part of F(1)F(o)-ATP synthase. The inclination of the proton pathway isolates the two half-channels and may contribute to a favorable clockwise rotation in ATP synthesis mode.
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Affiliation(s)
- Holger Gohlke
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich Heine University, 40204 Düsseldorf, Germany
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20
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Pierson HE, Uhlemann EME, Dmitriev OY. Interaction with monomeric subunit c drives insertion of ATP synthase subunit a into the membrane and primes a-c complex formation. J Biol Chem 2011; 286:38583-38591. [PMID: 21900248 DOI: 10.1074/jbc.m111.294868] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Subunit a is the main part of the membrane stator of the ATP synthase molecular turbine. Subunit c is the building block of the membrane rotor. We have generated two molecular fusions of a and c subunits with different orientations of the helical hairpin of subunit c. The a/c fusion protein with correct orientation of transmembrane helices was inserted into the membrane, and co-incorporated into the F(0) complex of ATP synthase with wild type subunit c. The fused c subunit was incorporated into the c-ring tethering the ATP synthase rotor to the stator. The a/c fusion with incorrect orientation of the c-helices required wild type subunit c for insertion into the membrane. In this case, the fused c subunit remained on the periphery of the c-ring and did not interfere with rotor movement. Wild type subunit a inserted into the membrane equally well with wild type subunit c and c-ring assembly mutants that remained monomeric in the membrane. These results show that interaction with monomeric subunit c triggers insertion of subunit a into the membrane, and initiates formation of the a-c complex, the ion-translocating module of the ATP synthase. Correct assembly of the ATP synthase incorporating topologically correct fusion of subunits a and c validates using this model protein for high resolution structural studies of the ATP synthase proton channel.
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Affiliation(s)
- Hannah E Pierson
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Eva-Maria E Uhlemann
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Oleg Y Dmitriev
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
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21
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Dong H, Fillingame RH. Chemical reactivities of cysteine substitutions in subunit a of ATP synthase define residues gating H+ transport from each side of the membrane. J Biol Chem 2010; 285:39811-8. [PMID: 20943664 DOI: 10.1074/jbc.m110.175844] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Subunit a plays a key role in coupling H(+) transport to rotations of the subunit c-ring in F(1)F(o) ATP synthase. In Escherichia coli, H(+) binding and release occur at Asp-61 in the middle of the second transmembrane helix (TMH) of F(o) subunit c. Based upon the Ag(+) sensitivity of Cys substituted into subunit a, H(+) are thought to reach Asp-61 via aqueous pathways mapping to surfaces of TMH 2-5. In this study we have extended characterization of the most Ag(+)-sensitive residues in subunit a with cysteine reactive methanethiosulfonate (MTS) reagents and Cd(2+). The effect of these reagents on ATPase-coupled H(+) transport was measured using inside-out membrane vesicles. Cd(2+) inhibited the activity of all Ag(+)-sensitive Cys on the cytoplasmic side of the TMHs, and three of these substitutions were also sensitive to inhibition by MTS reagents. On the other hand, Cd(2+) did not inhibit the activities of substitutions at residues 119 and 120 on the periplasmic side of TMH2, and residues 214 and 215 in TMH4 and 252 in TMH5 at the center of the membrane. When inside-out membrane vesicles from each of these substitutions were sonicated during Cd(2+) treatment to expose the periplasmic surface, the ATPase-coupled H(+) transport activity was strongly inhibited. The periplasmic access to N214C and Q252C, and their positioning in the protein at the a-c interface, is consistent with previous proposals that these residues may be involved in gating H(+) access from the periplasmic half-channel to Asp-61 during the protonation step.
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Affiliation(s)
- Hui Dong
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706, USA
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22
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Essential arginine residue of the F(o)-a subunit in F(o)F(1)-ATP synthase has a role to prevent the proton shortcut without c-ring rotation in the F(o) proton channel. Biochem J 2010; 430:171-7. [PMID: 20518749 DOI: 10.1042/bj20100621] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In F(o)F(1) (F(o)F(1)-ATP synthase), proton translocation through F(o) drives rotation of the oligomer ring of F(o)-c subunits (c-ring) relative to F(o)-a. Previous reports have indicated that a conserved arginine residue in F(o)-a plays a critical role in the proton transfer at the F(o)-a/c-ring interface. Indeed, we show in the present study that thermophilic F(o)F(1s) with substitution of this arginine (aR169) to other residues cannot catalyse proton-coupled reactions. However, mutants with substitution of this arginine residue by a small (glycine, alanine, valine) or acidic (glutamate) residue mediate the passive proton translocation. This translocation requires an essential carboxy group of F(o)-c (cE56) since the second mutation (cE56Q) blocks the translocation. Rotation of the c-ring is not necessary because the same arginine mutants of the 'rotation-impossible' (c(10)-a)F(o)F(1), in which the c-ring and F(o)-a are fused to a single polypeptide, also exhibits the passive proton translocation. The mutant (aR169G/Q217R), in which the arginine residue is transferred to putatively the same topological position in the F(o)-a structure, can block the passive proton translocation. Thus the conserved arginine residue in F(o)-a ensures proton-coupled c-ring rotation by preventing a futile proton shortcut.
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23
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Mogi T, Kita K. Identification of mitochondrial Complex II subunits SDH3 and SDH4 and ATP synthase subunits a and b in Plasmodium spp. Mitochondrion 2009; 9:443-53. [PMID: 19682605 DOI: 10.1016/j.mito.2009.08.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Revised: 08/03/2009] [Accepted: 08/06/2009] [Indexed: 01/06/2023]
Abstract
While most protist mitochondrial enzymes could be identified in database, the membrane anchor subunits of Complex II and F(o)F(1)-ATP synthase of malaria parasites are not annotated. Based on the presence of structural fingerprints or proteomics data from other protists, here we present their candidates. In contrast to canonical subunits, Plasmodium Complex II anchors have two transmembrane helices and may coordinate heme b via Tyr in place of His. Transmembrane helix IV of ATP synthase subunit a lacks an essential Arg residue. Membrane anchors of Plasmodium Complex II and ATP synthase are divergent from orthologs and promising targets for new chemotherapeutics.
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Affiliation(s)
- Tatsushi Mogi
- Department of Biomedical Chemistry, The University of Tokyo, Hongo, Bunkyo-ku, Japan.
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24
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Bae L, Vik SB. A more robust version of the Arginine 210-switched mutant in subunit a of the Escherichia coli ATP synthase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1129-34. [PMID: 19362069 DOI: 10.1016/j.bbabio.2009.03.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Revised: 03/30/2009] [Accepted: 03/31/2009] [Indexed: 10/20/2022]
Abstract
Previous work has shown that the essential R210 of subunit a in the Escherichia coli ATP synthase can be switched with a conserved glutamine Q252 with retention of a moderate level of function, that a third mutation P204T enhances this function, and that the arginine Q252R can be replaced by lysine without total loss of activity. In this study, the roles of P204T and R210Q were examined. It was concluded that the threonine in P204T is not directly involved in function since its replacement by alanine did not significantly affect growth properties. Similarly, it was concluded that the glutamine in R210Q is not directly involved with function since replacement by glycine results in significantly enhanced function. Not only did the rate of ATP-driven proton translocation increase, but also the sensitivity of ATP hydrolysis to inhibition by N,N'-dicyclohexylcarbodiimide (DCCD) rose to more than 50%. Finally, mutations at position E219, a residue near the proton pathway, were used to test whether the Arginine-switched mutant uses the normal proton pathway. In a wild type background, the E219K mutant was confirmed to have greater function than the E219Q mutant, as has been shown previously. This same unusual result was observed in the triple mutant background, P204T/R210Q/Q252R, suggesting that the Arginine-switched mutants are using the normal proton pathway from the periplasm.
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Affiliation(s)
- Leon Bae
- Southern Methodist University, Department of Biological Sciences, Dallas, TX 75275-0376, USA
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25
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Liu J, Fujisawa M, Hicks DB, Krulwich TA. Characterization of the Functionally Critical AXAXAXA and PXXEXXP Motifs of the ATP Synthase c-Subunit from an Alkaliphilic Bacillus. J Biol Chem 2009; 284:8714-25. [PMID: 19176524 DOI: 10.1074/jbc.m808738200] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The membrane-embedded rotor in the F(0) sector of proton-translocating ATP synthases is formed from hairpin-like c-subunits that are protonated and deprotonated during energization of ATP synthesis. This study focuses on two c-subunit motifs that are unique to synthases of extremely alkaliphilic Bacillus species. One motif is the AXAXAXA sequence found in the N-terminal helix-1 instead of the GXGXGXG of non-alkaliphiles. Quadruple A-->G chromosomal mutants of alkaliphilic Bacillus pseudofirmus OF4 retain 50% of the wild-type hydrolytic activity (ATPase) but <18% of the ATP synthase capacity at high pH. Consistent with a structural impact of the four alanine replacements, the mutant ATPase activity showed enhanced inhibition by dicyclohexylcarbodiimide, which blocks the helix-2 carboxylate. Single, double, or triple A-->G mutants exhibited more modest defects, as monitored by malate growth. The key carboxylate is in the second motif, which is P(51)XXE(54)XXP in extreme alkaliphiles instead of the (A/G)XX(E/D)XXP found elsewhere. Mutation of Pro(51) to alanine had been shown to severely reduce malate growth and ATP synthesis at high pH. Here, two Pro(51) to glycine mutants of different severities retained ATP synthase capacity but exhibited growth deficits and proton leakiness. A Glu(54) to Asp(54) change increased proton leakiness and reduced malate growth 79-90%. The Pro(51) and the Glu(54) mutants were both more dicyclohexylcarbodiimide-sensitive than wild type. The results highlight the requirement for c-subunit adaptations to achieve alkaliphile ATP synthesis with minimal cytoplasmic proton loss and suggest partial suppression of some mutations by changes outside the atp operon.
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Affiliation(s)
- Jun Liu
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, New York 10029, USA
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26
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Proton Translocation and ATP Synthesis by the FoF1-ATPase of Purple Bacteria. THE PURPLE PHOTOTROPHIC BACTERIA 2009. [DOI: 10.1007/978-1-4020-8815-5_24] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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27
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Moore KJ, Fillingame RH. Structural interactions between transmembrane helices 4 and 5 of subunit a and the subunit c ring of Escherichia coli ATP synthase. J Biol Chem 2008; 283:31726-35. [PMID: 18786930 DOI: 10.1074/jbc.m803848200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Subunit a plays a key role in promoting H+ transport and the coupled rotary motion of the subunit c ring in F1F0-ATP synthase. H+ binding and release occur at Asp-61 in the middle of the second transmembrane helix (TMH) of F0 subunit c. H+ are thought to reach Asp-61 via aqueous pathways mapping to the surfaces of TMHs 2-5 of subunit a. TMH4 of subunit a is thought to pack close to TMH2 of subunit c based upon disulfide cross-link formation between Cys substitutions in both TMHs. Here we substituted Cys into the fifth TMH of subunit a and the second TMH of subunit c and tested for cross-linking using bis-methanethiosulfonate (bis-MTS) reagents. A total of 62 Cys pairs were tested and 12 positive cross-links were identified with variable alkyl length linkers. Cross-linking was achieved near the middle of the bilayer for the Cys pairs a248C/c62C, a248C/ c63C, a248C/c65C, a251C/c57C, a251C/c59C, a251C/c62C, a252C/c62C, and a252C/c65C. Cross-linking was achieved near the cytoplasmic side of the bilayer for Cys pairs a262C/c53C, a262C/c54C, a262C/c55C, and a263C/c54C. We conclude that both aTMH4 and aTMH5 pack proximately to cTMH2 of the c-ring. In other experiments we demonstrate that aTMH4 and aTMH5 can be simultaneously cross-linked to different subunit c monomers in the c-ring. Five mutants showed pH-dependent cross-linking consistent with aTMH5 changing conformation at lower pH values to facilitate cross-linking. We suggest that the pH-dependent conformational change may be related to the proposed role of aTMH5 in gating H+ access from the periplasm to the cAsp-61 residue in cTMH2.
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Affiliation(s)
- Kyle J Moore
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706, USA
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28
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Moore KJ, Angevine CM, Vincent OD, Schwem BE, Fillingame RH. The cytoplasmic loops of subunit a of Escherichia coli ATP synthase may participate in the proton translocating mechanism. J Biol Chem 2008; 283:13044-52. [PMID: 18337242 DOI: 10.1074/jbc.m800900200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Subunit a plays a key role in promoting H(+) transport and the coupled rotary motion of the subunit c ring in F(1)F(0)-ATP synthase. H(+) binding and release occur at Asp-61 in the middle of the second transmembrane helix (TMH) of F(0) subunit c. H(+) are thought to reach Asp-61 via aqueous pathways mapping to the surfaces of TMHs 2-5 of subunit a based upon the chemical reactivity of Cys substituted into these helices. Here we substituted Cys into loops connecting TMHs 1 and 2 (loop 1-2) and TMHs 3 and 4 (loop 3-4). A large segment of loop 3-4 extending from loop residue 192 loop to residue 203 in TMH4 at the lipid bilayer surface proved to be very sensitive to inhibition by Ag(+). Cys-161 and -165 at the other end of the loop bordering TMH3 were also sensitive to inhibition by Ag(+). Further Cys substitutions in residues 86 and 93 in the middle of the 1-2 loop proved to be Ag(+)-sensitive. We next asked whether the regions of Ag(+)-sensitive residues clustered together near the surface of the membrane by combining Cys substitutions from two domains and testing for cross-linking. Cys-161 and -165 in loop 3-4 were found to cross-link with Cys-202, -203, or -205, which extend into TMH4 from the cytoplasm. Further Cys at residues 86 and 93 in loop 1-2 were found to cross-link with Cys-195 in loop 3-4. We conclude that the Ag(+)-sensitive regions of loops 1-2 and 3-4 may pack in a single domain that packs at the ends of TMHs 3 and 4. We suggest that the Ag(+)-sensitive domain may be involved in gating H(+) release at the cytoplasmic side of the aqueous access channel extending through F(0).
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Affiliation(s)
- Kyle J Moore
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
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29
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Devenish RJ, Prescott M, Rodgers AJW. The structure and function of mitochondrial F1F0-ATP synthases. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 267:1-58. [PMID: 18544496 DOI: 10.1016/s1937-6448(08)00601-1] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We review recent advances in understanding of the structure of the F(1)F(0)-ATP synthase of the mitochondrial inner membrane (mtATPase). A significant achievement has been the determination of the structure of the principal peripheral or stator stalk components bringing us closer to achieving the Holy Grail of a complete 3D structure for the complex. A major focus of the field in recent years has been to understand the physiological significance of dimers or other oligomer forms of mtATPase recoverable from membranes and their relationship to the structure of the cristae of the inner mitochondrial membrane. In addition, the association of mtATPase with other membrane proteins has been described and suggests that further levels of functional organization need to be considered. Many reports in recent years have concerned the location and function of ATP synthase complexes or its component subunits on the external surface of the plasma membrane. We consider whether the evidence supports complete complexes being located on the cell surface, the biogenesis of such complexes, and aspects of function especially related to the structure of mtATPase.
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Affiliation(s)
- Rodney J Devenish
- Department of Biochemistry and Molecular Biology, and ARC Centre of Excellence in Microbial Structural and Functional Genomics, Monash University, Clayton Campus, Victoria, 3800, Australia
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30
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Interaction of transmembrane helices in ATP synthase subunit a in solution as revealed by spin label difference NMR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1777:227-37. [PMID: 18178144 DOI: 10.1016/j.bbabio.2007.11.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 11/28/2007] [Accepted: 11/29/2007] [Indexed: 11/30/2022]
Abstract
Subunit a in the membrane traversing F0 sector of Escherichia coli ATP synthase is known to fold with five transmembrane helices (TMHs) with residue 218 in TMH IV packing close to residue 248 in TMH V. In this study, we have introduced a spin label probe at Cys residues substituted at positions 222 or 223 and measured the effects on the Trp epsilon NH indole NMR signals of the seven Trp residues in the protein. The protein was purified and NMR experiments were carried out in a chloroform-methanol-H2O (4:4:1) solvent mixture. The spin label at positions 222 or 223 proved to broaden the signals of W231, W232, W235 and W241 located at the periplasmic ends of TMH IV and TMH V and the connecting loop between these helices. The broadening of W241 would require that the loop residues fold back on themselves in a hairpin-like structure much like it is predicted to fold in the native membrane. Placement of the spin label probe at several other positions also proved to have broadening effects on some of these Trp residues and provided additional constraints on folding of TMH IV and TMH V. The effects of the 223 probes on backbone amide resonances of subunit a were also measured by an HNCO experiment and the results are consistent with the two helices folding back on themselves in this solvent mixture. When Cys and Trp were substituted at residues 206 and 254 at the cytoplasmic ends of TMHs IV and V respectively, the W254 resonance was not broadened by the spin label at position 206. We conclude that the helices fold back on themselves in this solvent system and then pack at an angle such that the cytoplasmic ends of the polypeptide backbone are significantly displaced from each other.
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31
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Ishmukhametov RR, Pond JB, Al-Huqail A, Galkin MA, Vik SB. ATP synthesis without R210 of subunit a in the Escherichia coli ATP synthase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1777:32-8. [PMID: 18068111 DOI: 10.1016/j.bbabio.2007.11.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Revised: 11/02/2007] [Accepted: 11/07/2007] [Indexed: 11/29/2022]
Abstract
Interactions between subunit a and oligomeric subunit c are essential for the coupling of proton translocation to rotary motion in the ATP synthase. A pair of previously described mutants, R210Q/Q252R and P204T/R210Q/Q252R [L.P. Hatch, G.B. Cox and S.M. Howitt, The essential arginine residue at position 210 in the a subunit of the Escherichia coli ATP synthase can be transferred to position 252 with partial retention of activity, J. Biol. Chem. 270 (1995) 29407-29412] has been constructed and further analyzed. These mutants, in which the essential arginine of subunit a, R210, was switched with a conserved glutamine residue, Q252, are shown here to be capable of both ATP synthesis by oxidative phosphorylation, and ATP-driven proton translocation. In addition, lysine can replace the arginine at position 252 with partial retention of both activities. The pH dependence of ATP-driven proton translocation was determined after purification of mutant enzymes, and reconstitution into liposomes. Proton translocation by the lysine mutant, and to a lesser extent the arginine mutant, dropped off sharply above pH 7.5, consistent with the requirement for a positive charge during function. Finally, the rates of ATP synthesis and of ATP-driven proton translocation were completely inhibited by treatment with DCCD (N,N'-dicyclohexylcarbodiimide), while rates of ATP hydrolysis by the mutants were not significantly affected, indicating that DCCD modification disrupts the F(1)-F(o) interface. The results suggest that minimal requirements for proton translocation by the ATP synthase include a positive charge in subunit a and a weak interface between subunit a and oligomeric subunit c.
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Affiliation(s)
- Robert R Ishmukhametov
- Department of Biological Sciences, Box 750376, Southern Methodist University, Dallas, TX 75275-0376, USA
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32
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Langemeyer L, Engelbrecht S. Essential arginine in subunit a and aspartate in subunit c of FoF1 ATP synthase: effect of repositioning within helix 4 of subunit a and helix 2 of subunit c. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:998-1005. [PMID: 17583672 DOI: 10.1016/j.bbabio.2007.05.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Revised: 05/10/2007] [Accepted: 05/21/2007] [Indexed: 10/23/2022]
Abstract
FoF1 ATP synthase couples proton flow through the integral membrane portion Fo (ab2c10) to ATP-synthesis in the extrinsic F1-part ((alphabeta)3gammadeltaepsilon) (Escherichia coli nomenclature and stoichiometry). Coupling occurs by mechanical rotation of subunits c10gammaepsilon relative to (alphabeta)3deltaab2. Two residues were found to be essential for proton flow through ab2c10, namely Arg210 in subunit a (aR210) and Asp61 in subunits c (cD61). Their deletion abolishes proton flow, but "horizontal" repositioning, by anchoring them in adjacent transmembrane helices, restores function. Here, we investigated the effects of "vertical" repositioning aR210, cD61, or both by one helical turn towards the N- or C-termini of their original helices. Other than in the horizontal the vertical displacement changes the positions of the side chains within the depth of the membrane. Mutant aR210A/aN214R appeared to be short-circuited in that it supported proton conduction only through EF1-depleted EFo, but not in EFoEF1, nor ATP-driven proton pumping. Mutant cD61N/cM65D grew on succinate, retained the ability to synthesize ATP and supported passive proton conduction but apparently not ATP hydrolysis-driven proton pumping.
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Affiliation(s)
- Lars Langemeyer
- Universität Osnabrück, Fachbereich Biologie, Biochemie, Barbarastr. 13, 49076 Osnabrück, Germany
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33
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Angevine CM, Herold KAG, Vincent OD, Fillingame RH. Aqueous access pathways in ATP synthase subunit a. Reactivity of cysteine substituted into transmembrane helices 1, 3, and 5. J Biol Chem 2007; 282:9001-7. [PMID: 17234633 DOI: 10.1074/jbc.m610848200] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Subunit a is thought to play a key role in H+ transport-driven rotation of the subunit c ring in Escherichia coli F1F0 ATP synthase. In the membrane-traversing F0 sector of the enzyme, H+ binding and release occurs at Asp-61 in the middle of the second transmembrane helix (TMH) of subunit c. Protons are thought to reach Asp-61 via aqueous channels formed at least in part by one or more of the five TMHs of subunit a. Aqueous access to surfaces of TMHs 2, 4, and 5 was previously suggested based upon the chemical reactivity of cysteine residues substituted into these helices. Here we have substituted Cys into TMH1 and TMH3 and extended the substitutions in TMH5 to the cytoplasmic surface. One region of TMH3 proved to be moderately Ag+-sensitive and may connect with the Ag+-sensitive region found previously on the periplasmic side of TMH2. A single Cys substitution in TMH1 proved to be both N-ethylmaleimide (NEM)-sensitive and Ag+-sensitive and suggests a possible packing interaction of TMH1 with TMH2 and TMH3. New Ag+- and NEM-sensitive residues were found at the cytoplasmic end of TMH5 and suggest a possible connection of this region to the NEM- and Ag+-sensitive region of TMH4 described previously. From the now complete pattern of TMH residue reactivity, we conclude that aqueous access from the periplasmic side of F0 to cAsp-61 at the center of the membrane is likely to be mediated by residues of TMHs 2, 3, 4, and 5 at the center of a four-helix bundle. Further, aqueous access between cAsp-61 and the cytoplasmic surface is likely to be mediated by residues in TMH4 and TMH5 at the exterior of the four-helix bundle that are in contact with the c-ring.
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Affiliation(s)
- Christine M Angevine
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706, USA
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34
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Schwem BE, Fillingame RH. Cross-linking between helices within subunit a of Escherichia coli ATP synthase defines the transmembrane packing of a four-helix bundle. J Biol Chem 2006; 281:37861-7. [PMID: 17035244 DOI: 10.1074/jbc.m607453200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Subunit a of F(1)F(0) ATP synthase is required in the H(+) transport driven rotation of the c-ring of F(0), the rotation of which is coupled to ATP synthesis in F(1). The three-dimensional structure of subunit a is unknown. In this study, Cys substitutions were introduced into two different transmembrane helices (TMHs) of subunit a, and the proximity of the thiol side chains was tested via attempted oxidative cross-linking to form the disulfide bond. Pairs of Cys substitutions were made in TMHs 2/3, 2/4, 2/5, 3/4, 3/5, and 4/5. Cu(+2)-catalyzed oxidation led to cross-link formation between Cys pairs L120C(TMH2) and S144C(TMH3), L120C(TMH2) and G218C(TMH4), L120C(TMH2) and H245C(TMH5), L120C(TMH2) and I246C(TMH5), N148C(TMH3) and E219C(TMH4), N148C(TMH3) and H245C(TMH5), and G218C(TMH4) and I248C(TMH5). Iodine, but not Cu(+2), was found to catalyze cross-link formation between D119C(TMH2) and G218C(TMH4). The results suggest that TMHs 2, 3, 4, and 5 form a four-helix bundle with one set of key functional residues in TMH4 (Ser-206, Arg-210, and Asn-214) located at the periphery facing subunit c. Other key residues in TMHs 2, 4, and 5, which were concluded previously to compose a possible aqueous access pathway from the periplasm, were found to locate to the inside of the four-helix bundle.
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Affiliation(s)
- Brian E Schwem
- Department of Biomolecular Chemistry, School of Medicine and Public Health University of Wisconsin, Madison, Wisconsin 53706, USA
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35
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Nath S. A novel systems biology/engineering approach solves fundamental molecular mechanistic problems in bioenergetics and motility. Process Biochem 2006. [DOI: 10.1016/j.procbio.2006.07.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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36
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Mulkidjanian AY. Proton in the well and through the desolvation barrier. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:415-27. [PMID: 16780789 DOI: 10.1016/j.bbabio.2006.04.023] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2006] [Revised: 04/25/2006] [Accepted: 04/28/2006] [Indexed: 11/18/2022]
Abstract
The concept of the membrane proton well was suggested by Peter Mitchell to account for the energetic equivalence of the chemical (DeltapH) and electrical (Deltapsi) components of the proton-motive force. The proton well was defined as a proton-conducting crevice passing down into the membrane dielectric and able to accumulate protons in response to the generation either of Deltapsi or of DeltapH. In this review, the concept of proton well is contrasted to the desolvation penalty of > 500 meV for transferring protons into the membrane core. The magnitude of the desolvation penalty argues against deep proton wells in the energy-transducing enzymes. The shallow DeltapH- and Deltapsi-sensitive proton traps, mechanistically linked to the functional groups in the membrane interior, seem more realistic. In such constructs, the draw of a trapped proton into the membrane core can happen at the expense of some exergonic reaction, e.g., release of another proton from the membrane into the aqueous phase. It is argued that the proton transfer in the ATP synthase and the cytochrome bc complex could proceed in this way.
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Affiliation(s)
- Armen Y Mulkidjanian
- A.N. Belozersky Institute of Physico-chemical Biology, Moscow State University, 119899, Moscow, Russia.
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37
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Tzen CY, Wu TY. Evolutional Analysis in Determining Pathogenic versus Nonpathogenic Mutations of ATPase 6 in Human Mitochondriopathy. Ann N Y Acad Sci 2006; 1042:19-24. [PMID: 15965041 DOI: 10.1196/annals.1338.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Because mitochondrial ATPase 6 plays an important role in ATP synthesis, mutations affecting ATPase 6 can undoubtedly cause human diseases. In contrast, the ATPase 6 gene is known to be a fast-evolving gene and has generated enough polymorphisms to allow identity investigation for forensic casework. To investigate these seemingly opposite views, we analyzed amino acid sequences of ATPase 6 in at least 1,266 humans, 102 mammals, and 213 vertebrates. The result showed that the amino acids of human ATPase 6 could be divided into the following four groups. Amino acid residue 192 (affected by alteration at nt 9101) and 79 other residues were variable, and therefore substitutions of these residues would not be pathogenic. Amino acid residue 156 (affected by alteration at nt 8993) and 93 other residues were conserved in Homo sapiens, but not in Mammalia. Therefore, they were potentially pathogenic if altered. Function studies would be necessary to confirm their role in pathogenesis. Amino acid residue 217 (affected by alteration at nt 9176) and 9 other residues were conserved across all species, including S. cerevisiae and E. coli. Mutations involving these residues would be pathogenic, some of which might even be life threatening. The remainder (42 residues) were conserved in Mammalia, but not in yeast and E. coli. They were probably pathogenic if mutated. The classification proposed in this study may, therefore, provide an algorithm for a diagnostic approach when a newly identified change of ATPase 6 is suspected for human mitochondriopathy.
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Affiliation(s)
- Chin-Yuan Tzen
- Department of Pathology, Mackay Memorial Hospital, 45, Minsheng Road, Tamshui, Taipei 251, Taiwan.
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38
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Dimroth P, Cook GM. Bacterial Na+- or H+-coupled ATP Synthases Operating at Low Electrochemical Potential. Adv Microb Physiol 2004; 49:175-218. [PMID: 15518831 DOI: 10.1016/s0065-2911(04)49004-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In certain strictly anaerobic bacteria, the energy for growth is derived entirely from a decarboxylation reaction. A prominent example is Propionigenium modestum, which converts the free energy of the decarboxylation of (S)-methylmalonyl-CoA to propionyl-CoA (DeltaG degrees =-20.6 kJ/mol) into an electrochemical Na(+) ion gradient across the membrane. This energy source is used as a driving force for ATP synthesis by a Na(+)-translocating F(1)F(0) ATP synthase. According to bioenergetic considerations, approximately four decarboxylation events are necessary to support the synthesis of one ATP. This unique feature of using Na(+) instead of H(+) as the coupling ion has made this ATP synthase the paradigm to study the ion pathway across the membrane and its relationship to rotational catalysis. The membrane potential (Deltapsi) is the key driving force to convert ion translocation through the F(0) motor components into torque. The resulting rotation elicits conformational changes at the catalytic sites of the peripheral F(1) domain which are instrumental for ATP synthesis. Alkaliphilic bacteria also face the challenge of synthesizing ATP at a low electrochemical potential, but for entirely different reasons. Here, the low potential is not the result of insufficient energy input from substrate degradation, but of an inverse pH gradient. This is a consequence of the high environmental pH where these bacteria grow and the necessity to keep the intracellular pH in the neutral range. In spite of this unfavorable bioenergetic condition, ATP synthesis in alkaliphilic bacteria is coupled to the proton motive force (DeltamuH(+)) and not to the much higher sodium motive force (DeltamuNa(+)). A peculiar feature of the ATP synthases of alkaliphiles is the specific inhibition of their ATP hydrolysis activity. This inhibition appears to be an essential strategy for survival at high external pH: if the enzyme were to operate as an ATPase, protons would be pumped outwards to counteract the low DeltamuH(+), thus wasting valuable ATP and compromising acidification of the cytoplasm at alkaline pH.
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Affiliation(s)
- Peter Dimroth
- Institut für Mikrobiologie, Eidgenössische Technische Hochschule, ETH-Zentrum, Schmelzbergstrasse 7, CH-8092 Zürich, Switzerland
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39
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Angevine CM, Herold KAG, Fillingame RH. Aqueous access pathways in subunit a of rotary ATP synthase extend to both sides of the membrane. Proc Natl Acad Sci U S A 2003; 100:13179-83. [PMID: 14595019 PMCID: PMC263739 DOI: 10.1073/pnas.2234364100] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The role of subunit a in promoting proton translocation and rotary motion in the Escherichia coli F1Fo ATP synthase is poorly understood. In the membrane-bound Fo sector of the enzyme, H+ binding and release occur at Asp-61 in the middle of the second transmembrane helix (TMH) of subunit c. Protons are thought to reach Asp-61 at the center of the membrane via aqueous channels formed at least in part by one or more of the five TMHs of subunit a. Aqueous access pathways have previously been mapped to surfaces of aTMH4. Here we have substituted Cys into the second and fifth TMHs of subunit a and carried out chemical modification with Ag+ and N-ethylmaleimide to define the aqueous accessibility of residues along these helices. Access to cAsp-61 at the center of the membrane may be mediated in part by Ag+-sensitive residues 248, 249, 251, and 252 in aTMH5. From the periplasmic surface, aqueous access to cAsp-61 may be mediated by silver-sensitive residues 115, 116, 119, 120, 122, and 126 in aTMH2. The Ag+-sensitive residues in TMH2, -4, and -5 form a continuum extending from the periplasmic to the cytoplasmic side of the membrane. In an arrangement of helices supported by second-site revertant and crosslinking analyses, these residues cluster at the interior of a four-helix bundle formed by TMH2-5. The aqueous access pathways at the interior of subunit a may be gated by a swiveling of helices in this bundle, alternately exposing cytoplasmic and periplasmic half channels to cAsp-61 during the H+ transport cycle.
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Affiliation(s)
- Christine M Angevine
- Department of Biomolecular Chemistry, University of Wisconsin Medical School, Madison, WI 53706, USA
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40
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Abstract
The role of subunit a in proton translocation by the Escherichia coli F(1)F(o) ATP synthase is poorly understood. In the membrane-bound F(o) sector of the enzyme, H(+) binding and release occurs at Asp(61) in the middle of the second transmembrane helix (TMH) of subunit c. Protons are thought to reach Asp(61) via an aqueous access pathway formed at least in part by one or more of the five TMHs of subunit a. In this report, we have substituted Cys into a 19-residue span of the fourth TMH of subunit a and used chemical modification to obtain information about the aqueous accessibility of residues along this helix. Residues 206, 210, and 214 are N-ethylmaleimide-accessible from the cytoplasmic side of the membrane and may lie on the H(+) transport route. Residues 215 and 218 on TMH4, as well as residue 245 on TMH5, are Ag(+)-accessible but N-ethylmaleimide-inaccessible and may form part of an aqueous pocket extending from Asp(61) of subunit c to the periplasmic surface.
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Affiliation(s)
- Christine M Angevine
- Department of Biomolecular Chemistry, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
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41
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Wehrle F, Kaim G, Dimroth P. Molecular mechanism of the ATP synthase's F(o) motor probed by mutational analyses of subunit a. J Mol Biol 2002; 322:369-81. [PMID: 12217697 DOI: 10.1016/s0022-2836(02)00731-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The most prominent residue of subunit a of the F(1)F(o) ATP synthase is a universally conserved arginine (aR227 in Propionigenium modestum), which was reported to permit no substitution with retention of ATP synthesis or H(+)-coupled ATP hydrolysis activity. We show here that ATP synthases with R227K or R227H mutations in the P.modestum a subunit catalyse ATP-driven Na(+) transport above or below pH 8.0, respectively. Reconstituted F(o) with either mutation catalysed 22Na(+)(out)/Na(+)(in) exchange with similar pH profiles as found in ATP-driven Na(+) transport. ATP synthase with an aR227A substitution catalysed Na(+)-dependent ATP hydrolysis, which was completely inhibited by dicyclohexylcarbodiimide, but not coupled to Na(+) transport. This suggests that in the mutant the dissociation of Na(+) becomes more difficult and that the alkali ions remain therefore permanently bound to the c subunit sites. The reconstituted mutant enzyme was also able to synthesise ATP in the presence of a membrane potential, which stopped at elevated external Na(+) concentrations. These observations reinforce the importance of aR227 to facilitate the dissociation of Na(+) from approaching rotor sites. This task of aR227 was corroborated by other results with the aR227A mutant: (i) after reconstitution into liposomes, F(o) with the aR227A mutation did not catalyse 22Na(+)(out)/Na(+)(in) exchange at high internal sodium concentrations, and (ii) at a constant (Delta)pNa(+), 22Na(+) uptake was inhibited at elevated internal Na(+) concentrations. Hence, in mutant aR227A, sodium ions can only dissociate from their rotor sites into a reservoir of low sodium ion concentration, whereas in the wild-type the positively charged aR227 allows the dissociation of Na(+) even into compartments of high Na(+) concentration.
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Affiliation(s)
- Franziska Wehrle
- Institut für Mikrobiologie, Eidgenössische Technische Hochschule, Schmelzbergstr. 7, CH-8092 Zürich, Switzerland
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42
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Fillingame RH, Angevine CM, Dmitriev OY. Coupling proton movements to c-ring rotation in F(1)F(o) ATP synthase: aqueous access channels and helix rotations at the a-c interface. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1555:29-36. [PMID: 12206887 DOI: 10.1016/s0005-2728(02)00250-5] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
F(1)F(o) ATP synthases generate ATP by a rotary catalytic mechanism in which H(+) transport is coupled to rotation of a ring of c subunits within the transmembrane sector of the enzyme. Protons bind to and then are released from the aspartyl-61 residue of subunit c at the center of the membrane. Proton access channels to and from aspartyl-61 are thought to form in subunit a of the F(o) sector. Here, we summarize new information on the structural organization of subunit a and the mapping of aqueous accessible residues in the fourth and fifth transmembrane helices (TMHs). Cysteine substituted residues, lying on opposite faces of aTMH-4, preferentially react with either N-ethyl-maleimide (NEM) or Ag(+). We propose that aTMH-4 rotates to alternately expose each helical face to aspartyl-61 of subunit c during the proton transport cycle. The concerted helical rotation of aTMH-4 and cTMH-2 are proposed to be coupled to the stepwise mechanical movement of the c-rotor.
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Affiliation(s)
- Robert H Fillingame
- Department of Biomolecular Chemistry, University of Wisconsin Medical School, Madison 53706-1532, USA.
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43
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Long JC, DeLeon-Rangel J, Vik SB. Characterization of the first cytoplasmic loop of subunit a of the Escherichia coli ATP synthase by surface labeling, cross-linking, and mutagenesis. J Biol Chem 2002; 277:27288-93. [PMID: 12021273 DOI: 10.1074/jbc.m202118200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The first cytoplasmic loop of subunit a of the Escherichia coli ATP synthase has been analyzed by cysteine substitution mutagenesis. 13 of the 26 residues tested were found to be accessible to the reaction with 3-(N-maleimidylpropionyl)-biocytin. The other 13 residues predominantly found in the central region of the polypeptide chain between the two transmembrane spans were more resistant to labeling by 3-(N-maleimidylpropionyl)-biocytin while in membrane vesicle preparations. This region of subunit a contains a conserved residue Glu-80, which when mutated to lysine resulted in a significant loss of ATP-driven proton translocation. Other substitutions including glutamine, alanine, and leucine were much less detrimental to function. Cross-linking studies with a photoactive cross-linking reagent were carried out. One mutant, K74C, was found to generate distinct cross-links to subunit b, and the cross-linking had little effect on proton translocation. The results indicate that the first transmembrane span (residues 40-64) of subunit a is probably near one or both of the b subunits and that a less accessible region of the first cytoplasmic loop (residues 75-90) is probably near the cytoplasmic surface, perhaps in contact with b subunits.
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Affiliation(s)
- Julie C Long
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275, USA
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44
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Kaim G. The Na(+)-translocating F(1)F(0) ATP synthase of Propionigenium modestum: mechanochemical insights into the F(0) motor that drives ATP synthesis. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1505:94-107. [PMID: 11248192 DOI: 10.1016/s0005-2728(00)00280-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The ATP synthase of Propionigenium modestum encloses a rotary motor involved in the production of ATP from ADP and inorganic phosphate utilizing the free energy of an electrochemical Na(+) ion gradient. This enzyme clearly belongs to the family of F(1)F(0) ATP synthases and uses exclusively Na(+) ions as the physiological coupling ion. The motor domain, F(0), comprises subunit a and the b subunit dimer which are part of the stator and the subunit c oligomer acting as part of the rotor. During ATP synthesis, Na(+) translocation through F(0) proceeds from the periplasm via the stator channel (subunit a) onto a Na(+) binding site of the rotor (subunit c). Upon rotation of the subunit c oligomer versus subunit a, the occupied rotor site leaves the interface with the stator and the Na(+) ion can freely dissociate into the cytoplasm. Recent experiments demonstrate that the membrane potential is crucial for ATP synthesis under physiological conditions. These findings support the view that voltage generates torque in F(0), which drives the rotation of the gamma subunit thus liberating tightly bound ATP from the catalytic sites in F(1). We suggest a mechanochemical model for the transduction of transmembrane Na(+)-motive force into rotary torque by the F(0) motor that can account quantitatively for the experimental data.
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Affiliation(s)
- G Kaim
- Institut für Mikrobiologie, Eidgenössische Technische Hochschule, ETH-Zentrum, Schmelzbergstrasse 7, CH-8092, Zürich, Switzerland.
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45
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Jones PC, Hermolin J, Jiang W, Fillingame RH. Insights into the rotary catalytic mechanism of F0F1 ATP synthase from the cross-linking of subunits b and c in the Escherichia coli enzyme. J Biol Chem 2000; 275:31340-6. [PMID: 10882728 DOI: 10.1074/jbc.m003687200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transmembrane sector of the F(0)F(1) rotary ATP synthase is proposed to organize with an oligomeric ring of c subunits, which function as a rotor, interacting with two b subunits at the periphery of the ring, the b subunits functioning as a stator. In this study, cysteines were introduced into the C-terminal region of subunit c and the N-terminal region of subunit b. Cys of N2C subunit b was cross-linked with Cys at positions 74, 75, and 78 of subunit c. In each case, a maximum of 50% of the b subunit could be cross-linked to subunit c, which suggests that either only one of the two b subunits lie adjacent to the c-ring or that both b subunits interact with a single subunit c. The results support a topological arrangement of these subunits, in which the respective N- and C-terminal ends of subunits b and c extend to the periplasmic surface of the membrane and cAsp-61 lies at the center of the membrane. The cross-linking of Cys between bN2C and cV78C was shown to inhibit ATP-driven proton pumping, as would be predicted from a rotary model for ATP synthase function, but unexpectedly, cross-linking did not lead to inhibition of ATPase activity. ATP hydrolysis and proton pumping are therefore uncoupled in the cross-linked enzyme. The c subunit lying adjacent to subunit b was shown to be mobile and to exchange with c subunits that initially occupied non-neighboring positions. The movement or exchange of subunits at the position adjacent to subunit b was blocked by dicyclohexylcarbodiimide. These experiments provide a biochemical verification that the oligomeric c-ring can move with respect to the b-stator and provide further support for a rotary catalytic mechanism in the ATP synthase.
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Affiliation(s)
- P C Jones
- Department of Biomolecular Chemistry, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
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46
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Abstract
The F(0)F(1) ATP synthase functions as a rotary motor where subunit rotation driven by a current of protons flowing through F(0) drives the binding changes in F(1) that are required for net ATP synthesis. Recent work that has led to the identification of components of the rotor and stator is reviewed. In addition, a model is proposed to describe the transmission of energy from four proton transport steps to the synthesis of one ATP. Finally, some of the requirements for efficient energy coupling by a rotary binding change mechanism are considered.
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Affiliation(s)
- R L Cross
- Department of Biochemistry and Molecular Biology, State University of New York, Health Science Center, Syracuse, NY 13210, USA.
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47
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Vik SB, Long JC, Wada T, Zhang D. A model for the structure of subunit a of the Escherichia coli ATP synthase and its role in proton translocation. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1458:457-66. [PMID: 10838058 DOI: 10.1016/s0005-2728(00)00094-3] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Most of what is known about the structure and function of subunit a, of the ATP synthase, has come from the construction and isolation of mutations, and their analysis in the context of the ATP synthase complex. Three classes of mutants will be considered in this review. (1) Cys substitutions have been used for structural analysis of subunit a, and its interactions with subunit c. (2) Functional residues have been identified by extensive mutagenesis. These studies have included the identification of second-site suppressors within subunit a. (3) Disruptive mutations include deletions at both termini, internal deletions, and single amino acid insertions. The results of these studies, in conjunction with information about subunits b and c, can be incorporated into a model for the mechanism of proton translocation in the Escherichia coli ATP synthase.
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Affiliation(s)
- S B Vik
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275, USA.
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Deckers-Hebestreit G, Greie J, Stalz W, Altendorf K. The ATP synthase of Escherichia coli: structure and function of F(0) subunits. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1458:364-73. [PMID: 10838051 DOI: 10.1016/s0005-2728(00)00087-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
In this review we discuss recent work from our laboratory concerning the structure and/or function of the F(0) subunits of the proton-translocating ATP synthase of Escherichia coli. For the topology of subunit a a brief discussion gives (i) a detailed picture of the C-terminal two-thirds of the protein with four transmembrane helices and the C terminus exposed to the cytoplasm and (ii) an evaluation of the controversial results obtained for the localization of the N-terminal region of subunit a including its consequences on the number of transmembrane helices. The structure of membrane-bound subunit b has been determined by circular dichroism spectroscopy to be at least 75% alpha-helical. For this purpose a method was developed, which allows the determination of the structure composition of membrane proteins in proteoliposomes. Subunit b was purified to homogeneity by preparative SDS gel electrophoresis, precipitated with acetone, and redissolved in cholate-containing buffer, thereby retaining its native conformation as shown by functional coreconstitution with an ac subcomplex. Monoclonal antibodies, which have their epitopes located within the hydrophilic loop region of subunit c, and the F(1) part are bound simultaneously to the F(0) complex without an effect on the function of F(0), indicating that not all c subunits are involved in F(1) interaction. Consequences on the coupling mechanism between ATP synthesis/hydrolysis and proton translocation are discussed.
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Affiliation(s)
- G Deckers-Hebestreit
- Abteilung Mikrobiologie, Fachbereich Biologie/Chemie, Universität Osnabrück, D-49069, Osnabrück, Germany.
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Fillingame RH, Jiang W, Dmitriev OY, Jones PC. Structural interpretations of F(0) rotary function in the Escherichia coli F(1)F(0) ATP synthase. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1458:387-403. [PMID: 10838053 DOI: 10.1016/s0005-2728(00)00089-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
F(1)F(0) ATP synthases are known to synthesize ATP by rotary catalysis in the F(1) sector of the enzyme. Proton translocation through the F(0) membrane sector is now proposed to drive rotation of an oligomer of c subunits, which in turn drives rotation of subunit gamma in F(1). The primary emphasis of this review will be on recent work from our laboratory on the structural organization of F(0), which proves to be consistent with the concept of a c(12) oligomeric rotor. From the NMR structure of subunit c and cross-linking studies, we can now suggest a detailed model for the organization of the c(12) oligomer in F(0) and some of the transmembrane interactions with subunits a and b. The structural model indicates that the H(+)-carrying carboxyl of subunit c is located between subunits of the c(12) oligomer and that two c subunits pack in a front-to-back manner to form the proton (cation) binding site. The proton carrying Asp61 side chain is occluded between subunits and access to it, for protonation and deprotonation via alternate entrance and exit half-channels, requires a swiveled opening of the packed c subunits and stepwise association with different transmembrane helices of subunit a. We suggest how some of the structural information can be incorporated into models of rotary movement of the c(12) oligomer during coupled synthesis of ATP in the F(1) portion of the molecule.
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Affiliation(s)
- R H Fillingame
- Department of Biomolecular Chemistry, University of Wisconsin Medical School, 1300 University Avenue, Madison, WI 53706, USA
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Baracca A, Barogi S, Carelli V, Lenaz G, Solaini G. Catalytic activities of mitochondrial ATP synthase in patients with mitochondrial DNA T8993G mutation in the ATPase 6 gene encoding subunit a. J Biol Chem 2000; 275:4177-82. [PMID: 10660580 DOI: 10.1074/jbc.275.6.4177] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We investigated the biochemical phenotype of the mtDNA T8993G point mutation in the ATPase 6 gene, associated with neurogenic muscle weakness, ataxia, and retinitis pigmentosa (NARP), in three patients from two unrelated families. All three carried >80% mutant genome in platelets and were manifesting clinically various degrees of the NARP phenotype. Coupled submitochondrial particles prepared from platelets capable of succinate-sustained ATP synthesis were studied using very sensitive and rapid luminometric and fluorescence methods. A sharp decrease (>95%) in the succinate-sustained ATP synthesis rate of the particles was found, but both the ATP hydrolysis rate and ATP-driven proton translocation (when the protons flow from the matrix to the cytosol) were minimally affected. The T8993G mutation changes the highly conserved residue Leu(156) to Arg in the ATPase 6 subunit (subunit a). This subunit, together with subunit c, is thought to cooperatively catalyze proton translocation and rotate, one with respect to the other, during the catalytic cycle of the F(1)F(0) complex. Our results suggest that the T8993G mutation induces a structural defect in human F(1)F(0)-ATPase that causes a severe impairment of ATP synthesis. This is possibly due to a defect in either the vectorial proton transport from the cytosol to the mitochondrial matrix or the coupling of proton flow through F(0) to ATP synthesis in F(1). Whatever mechanism is involved, this leads to impaired ATP synthesis. On the other hand, ATP hydrolysis that involves proton flow from the matrix to the cytosol is essentially unaffected.
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Affiliation(s)
- A Baracca
- Dipartimento di Biochimica, Università di Bologna, 48026 Bologna, Italy
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