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Yin X, Struik PC. Mathematical review of the energy transduction stoichiometries of C(4) leaf photosynthesis under limiting light. PLANT, CELL & ENVIRONMENT 2012; 35:1299-312. [PMID: 22321164 DOI: 10.1111/j.1365-3040.2012.02490.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A generalized model for electron (e(-) ) transport limited C(4) photosynthesis of NAD-malic enzyme and NADP-malic enzyme subtypes is presented. The model is used to review the thylakoid stoichiometries in vivo under strictly limiting light conditions, using published data on photosynthetic quantum yield and on photochemical efficiencies of photosystems (PS). Model review showed that cyclic e(-) transport (CET), rather than direct O(2) photoreduction, most likely contributed significantly to the production of extra ATP required for the C(4) cycle. Estimated CET, and non-cyclic e(-) transport supporting processes like nitrogen reduction, accounted for ca. 45 and 7% of total photosystem I (PSI) e(-) fluxes, respectively. The factor for excitation partitioning to photosystem II (PSII) was ca. 0.4. Further model analysis, in terms of the balanced NADPH: ATP ratio required for metabolism, indicated that: (1) the Q-cycle is obligatory; (2) the proton: ATP ratio is 4; and (3) the efficiency of proton pumping per e(-) transferred through the cytochrome b(6) /f complex is the same for CET and non-cyclic pathways. The analysis also gave an approach to theoretically assess CO(2) leakiness from bundle-sheath cells, and projected a leakiness of 0.07-0.16. Compared with C(3) photosynthesis, the most striking C(4) stoichiometry is its high fraction of CET.
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Affiliation(s)
- Xinyou Yin
- Centre for Crop Systems Analysis, Department of Plant Sciences, Wageningen University, P. O. Box 430, 6700 AK Wageningen, The Netherlands.
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52
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Comparison of the H+/ATP ratios of the H+-ATP synthases from yeast and from chloroplast. Proc Natl Acad Sci U S A 2012; 109:11150-5. [PMID: 22733773 DOI: 10.1073/pnas.1202799109] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
F(0)F(1)-ATP synthases use the free energy derived from a transmembrane proton transport to synthesize ATP from ADP and inorganic phosphate. The number of protons translocated per ATP (H(+)/ATP ratio) is an important parameter for the mechanism of the enzyme and for energy transduction in cells. Current models of rotational catalysis predict that the H(+)/ATP ratio is identical to the stoichiometric ratio of c-subunits to β-subunits. We measured in parallel the H(+)/ATP ratios at equilibrium of purified F(0)F(1)s from yeast mitochondria (c/β = 3.3) and from spinach chloroplasts (c/β = 4.7). The isolated enzymes were reconstituted into liposomes and, after energization of the proteoliposomes with acid-base transitions, the initial rates of ATP synthesis and hydrolysis were measured as a function of ΔpH. The equilibrium ΔpH was obtained by interpolation, and from its dependency on the stoichiometric ratio, [ATP]/([ADP]·[P(i)]), finally the thermodynamic H(+)/ATP ratios were obtained: 2.9 ± 0.2 for the mitochondrial enzyme and 3.9 ± 0.3 for the chloroplast enzyme. The data show that the thermodynamic H(+)/ATP ratio depends on the stoichiometry of the c-subunit, although it is not identical to the c/β ratio.
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Abstract
ATP synthase membrane rotors consist of a ring of c-subunits whose stoichiometry is constant for a given species but variable across different ones. We investigated the importance of c/c-subunit contacts by site-directed mutagenesis of a conserved stretch of glycines (GxGxGxGxG) in a bacterial c(11) ring. Structural and biochemical studies show a direct, specific influence on the c-subunit stoichiometry, revealing c(<11), c(12), c(13), c(14), and c(>14) rings. Molecular dynamics simulations rationalize this effect in terms of the energetics and geometry of the c-subunit interfaces. Quantitative data from a spectroscopic interaction study demonstrate that the complex assembly is independent of the c-ring size. Real-time ATP synthesis experiments in proteoliposomes show the mutant enzyme, harboring the larger c(12) instead of c(11), is functional at lower ion motive force. The high degree of compliance in the architecture of the ATP synthase rotor offers a rationale for the natural diversity of c-ring stoichiometries, which likely reflect adaptations to specific bioenergetic demands. These results provide the basis for bioengineering ATP synthases with customized ion-to-ATP ratios, by sequence modifications.
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54
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Soga N, Kinosita K, Yoshida M, Suzuki T. Kinetic equivalence of transmembrane pH and electrical potential differences in ATP synthesis. J Biol Chem 2012; 287:9633-9. [PMID: 22253434 PMCID: PMC3308813 DOI: 10.1074/jbc.m111.335356] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 01/12/2012] [Indexed: 11/06/2022] Open
Abstract
ATP synthase is the key player of Mitchell's chemiosmotic theory, converting the energy of transmembrane proton flow into the high energy bond between ADP and phosphate. The proton motive force that drives this reaction consists of two components, the pH difference (ΔpH) across the membrane and transmembrane electrical potential (Δψ). The two are considered thermodynamically equivalent, but kinetic equivalence in the actual ATP synthesis is not warranted, and previous experimental results vary. Here, we show that with the thermophilic Bacillus PS3 ATP synthase that lacks an inhibitory domain of the ε subunit, ΔpH imposed by acid-base transition and Δψ produced by valinomycin-mediated K(+) diffusion potential contribute equally to the rate of ATP synthesis within the experimental range examined (ΔpH -0.3 to 2.2, Δψ -30 to 140 mV, pH around the catalytic domain 8.0). Either ΔpH or Δψ alone can drive synthesis, even when the other slightly opposes. Δψ was estimated from the Nernst equation, which appeared valid down to 1 mm K(+) inside the proteoliposomes, due to careful removal of K(+) from the lipid.
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Affiliation(s)
- Naoki Soga
- From the Department of Physics, Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Kazuhiko Kinosita
- From the Department of Physics, Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Masasuke Yoshida
- the International Cooperative Research Project (ICORP) ATP Synthesis Regulation Project, Japan Science and Technology Agency, 2-3-6 Aomi, Koto-ku, Tokyo 135-0064, Japan, and
- the Department of Molecular Bioscience, Kyoto Sangyo University, Kamigamo-Motoyama, Kyoto 603-8555, Japan
| | - Toshiharu Suzuki
- the International Cooperative Research Project (ICORP) ATP Synthesis Regulation Project, Japan Science and Technology Agency, 2-3-6 Aomi, Koto-ku, Tokyo 135-0064, Japan, and
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Yoshizawa S, Kawanabe A, Ito H, Kandori H, Kogure K. Diversity and functional analysis of proteorhodopsin in marine Flavobacteria. Environ Microbiol 2012; 14:1240-8. [DOI: 10.1111/j.1462-2920.2012.02702.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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56
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Foyer CH, Neukermans J, Queval G, Noctor G, Harbinson J. Photosynthetic control of electron transport and the regulation of gene expression. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:1637-61. [PMID: 22371324 DOI: 10.1093/jxb/ers013] [Citation(s) in RCA: 273] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The term 'photosynthetic control' describes the short- and long-term mechanisms that regulate reactions in the photosynthetic electron transport (PET) chain so that the rate of production of ATP and NADPH is coordinated with the rate of their utilization in metabolism. At low irradiances these mechanisms serve to optimize light use efficiency, while at high irradiances they operate to dissipate excess excitation energy as heat. Similarly, the production of ATP and NADPH in ratios tailored to meet demand is finely tuned by a sophisticated series of controls that prevents the accumulation of high NAD(P)H/NAD(P) ratios and ATP/ADP ratios that would lead to potentially harmful over-reduction and inactivation of PET chain components. In recent years, photosynthetic control has also been extrapolated to the regulation of gene expression because mechanisms that are identical or similar to those that serve to regulate electron flow through the PET chain also coordinate the regulated expression of genes encoding photosynthetic proteins. This requires coordinated gene expression in the chloroplasts, mitochondria, and nuclei, involving complex networks of forward and retrograde signalling pathways. Photosynthetic control operates to control photosynthetic gene expression in response to environmental and metabolic changes. Mining literature data on transcriptome profiles of C(3) and C(4) leaves from plants grown under high atmospheric carbon dioxide (CO(2)) levels compared with those grown with ambient CO(2) reveals that the transition to higher photorespiratory conditions in C(3) plants enhances the expression of genes associated with cyclic electron flow pathways in Arabidopsis thaliana, consistent with the higher ATP requirement (relative to NADPH) of photorespiration.
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Affiliation(s)
- Christine H Foyer
- Centre for Plant Sciences, Faculty of Biology, University of Leeds, Leeds LS2 9JT, UK.
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57
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Ernst S, Düser MG, Zarrabi N, Börsch M. Three-color Förster resonance energy transfer within single F₀F₁-ATP synthases: monitoring elastic deformations of the rotary double motor in real time. JOURNAL OF BIOMEDICAL OPTICS 2012; 17:011004. [PMID: 22352638 DOI: 10.1117/1.jbo.17.1.011004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Catalytic activities of enzymes are associated with elastic conformational changes of the protein backbone. Förster-type resonance energy transfer, commonly referred to as FRET, is required in order to observe the dynamics of relative movements within the protein. Förster-type resonance energy transfer between two specifically attached fluorophores provides a ruler with subnanometer resolution between 3 and 8 nm, submillisecond time resolution for time trajectories of conformational changes, and single-molecule sensitivity to overcome the need for synchronization of various conformations. F(O)F(1)-ATP synthase is a rotary molecular machine which catalyzes the formation of adenosine triphosphate (ATP). The Escherichia coli enzyme comprises a proton driven 10 stepped rotary F(O) motor connected to a 3-stepped F(1) motor, where ATP is synthesized. This mismatch of step sizes will result in elastic deformations within the rotor parts. We present a new single-molecule FRET approach to observe both rotary motors simultaneously in a single F(O)F(1)-ATP synthase at work. We labeled this enzyme with three fluorophores, specifically at the stator part and at the two rotors. Duty cycle-optimized with alternating laser excitation, referred to as DCO-ALEX, allowed to control enzyme activity and to unravel associated transient twisting within the rotors of a single enzyme during ATP hydrolysis and ATP synthesis. Monte Carlo simulations revealed that the rotor twisting is larger than 36 deg.
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Affiliation(s)
- Stefan Ernst
- University of Stuttgart, 3rd Institute of Physics, Pfaffenwaldring 57, 70550 Stuttgart, Germany
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58
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Measurement of chloroplast ATP synthesis activity in Arabidopsis. Methods Mol Biol 2011. [PMID: 21863453 DOI: 10.1007/978-1-61779-237-3_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
There are numerous options for monitoring ATP synthesis in chloroplasts using isolated thylakoid membranes, intact chloroplasts, and even whole leaves. Currently, the most commonly used method employs isolated thylakoids coupling the synthesis of ATP to light emission from luciferin in a reaction catalyzed by luciferase. The luciferin-luciferase assay can be highly sensitive and is a direct measure of ATP. Another direct measurement of ATP is the incorporation of 32P into ATP, which, while more technically difficult, has the advantage over the luciferin-luciferase assay of being able to distinguish newly synthesized from total ATP. The phosphorylation of ADP results in a net decrease in pKa (acid disassociation constant) between the reactants and the product ATP, resulting in an increase in the pH of the assay media, which can be used as a convenient, continuous measurement of ATP synthesis. The formation of ΔμH+ across the thylakoid membrane and its concomitant dissipation as ATP is synthesized can be measured by an electrochromic absorption band shift (ECS) of thylakoid pigments measured at 518 nm (Witt, Biochim. Biophys. Acta 505:355-427, 1979; Petty and Jackson, Biochim. Biophys. Acta: Bioenergetics 547:463-473, 1979). The first-order decay time of the ESC can be used to estimate the rate of ATP synthesis providing a noninvasive, indirect method for measuring ATP synthase activity that can be used with intact leaves.
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59
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Oja V, Eichelmann H, Laisk A. The size of the lumenal proton pool in leaves during induction and steady-state photosynthesis. PHOTOSYNTHESIS RESEARCH 2011; 110:73-88. [PMID: 22002818 DOI: 10.1007/s11120-011-9697-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 09/28/2011] [Indexed: 05/16/2023]
Abstract
This report describes a new method to measure the chloroplastic lumenal proton pool in leaves (tobacco and sunflower). The method is based on measurement of CO(2) outbursts from leaves caused by the shift in the CO(2) + H(2)O ↔ HCO(3)(-) + H(+) equilibrium in the chloroplast stroma as protons return from the lumen after darkening. Protons did not accumulate in the lumen to a significant extent when photosynthesis was light-limited, but a large pool of >100 μmol H(+) m(-2) accumulated in the lumen as photosynthesis became light-saturated. During thylakoid energization in the light, large amounts of protons are moved from binding sites in the stroma to binding sites in the lumen. The transthylakoidal difference in the chemical potential of free protons (ΔpH) is largely based on the difference in the chemical potential of bound protons in the lumenal and stromal compartments (pK). Over the course of the dark-light induction of photosynthesis protons accumulate in the lumen during reduction of 3-phosphoglycerate. The accumulation of electrons in reduced compounds of the stroma and cytosol is the natural cause for accumulation of a stoichiometric pool of lumenal protons during this transient event.
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Affiliation(s)
- Vello Oja
- Institute of Molecular and Cellular Biology, University of Tartu, Riia St. 23, 51010 Tartu, Estonia
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60
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Ifuku K, Endo T, Shikanai T, Aro EM. Structure of the chloroplast NADH dehydrogenase-like complex: nomenclature for nuclear-encoded subunits. PLANT & CELL PHYSIOLOGY 2011; 52:1560-8. [PMID: 21785130 DOI: 10.1093/pcp/pcr098] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The chloroplast NADH dehydrogenase-like complex (NDH) was first discovered based on its similarity to complex I in respiratory electron transport, and is involved in electron transport from photoproduced stromal reductants such as NADPH and ferredoxin to the intersystem plastoqunone pool. However, a recent study suggested that it is a ferredoxin-dependent plastoquinone reductase rather than an NAD(P)H dehydrogenase. Furthermore, recent advances in subunit analysis of NDH have revealed the presence of a novel hydrophilic subcomplex on the stromal side of the thylakoid membrane, as well as an unexpected lumenal subcomplex. This review discusses these new studies on the structure of NDH, and proposes a unified nomenclature for newly discovered NDH subunits.
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Affiliation(s)
- Kentaro Ifuku
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto, 606-8502 Japan
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61
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Qian J, Liang J. Monte Carlo simulation from proton slip to "coupled" proton flow in ATP synthase based on the bi-site mechanism. Biosystems 2011; 105:233-7. [PMID: 21664229 DOI: 10.1016/j.biosystems.2011.05.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 03/04/2011] [Accepted: 05/05/2011] [Indexed: 11/17/2022]
Abstract
ATP synthase couples proton flow to ATP synthesis, but is leaky to protons at very low nucleotide concentration. Based on the bi-site mechanism, we simulated the proton conduction from proton slip to "coupled" proton flow in ATP synthase using the Monte Carlo method. Good agreement is obtained between the simulated and available experimental results. Our model provides deeper insight into the nucleotide dependence of ATP catalysis, and the kinetic cooperativity in three catalysis subunits. The results of simulation support the bi-site mechanism in ATP synthesis.
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Affiliation(s)
- Jun Qian
- School of Physics, Nankai University, No. 94 Weijing Road, Nankai District, Tianjin, China.
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62
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Thauer RK. Anaerobic oxidation of methane with sulfate: on the reversibility of the reactions that are catalyzed by enzymes also involved in methanogenesis from CO2. Curr Opin Microbiol 2011; 14:292-9. [DOI: 10.1016/j.mib.2011.03.003] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 03/13/2011] [Accepted: 03/15/2011] [Indexed: 11/16/2022]
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63
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Chinopoulos C. The "B space" of mitochondrial phosphorylation. J Neurosci Res 2011; 89:1897-904. [PMID: 21541983 DOI: 10.1002/jnr.22659] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 02/09/2011] [Accepted: 03/10/2011] [Indexed: 11/07/2022]
Abstract
It was recently shown that, in progressively depolarizing mitochondria, the F(0) -F(1) ATP synthase and the adenine nucleotide translocase (ANT) may change directionality independently from each other (Chinopoulos et al. [2010] FASEB J. 24:2405). When the membrane potentials at which these two molecular entities reverse directionality, termed reversal potential (Erev), are plotted as a function of matrix ATP/ADP ratio, an area of the plot is bracketed by the Erev_ATPase and the Erev_ANT, which we call "B space". Both reversal potentials are dynamic, in that they depend on the fluctuating values of the participating reactants; however, Erev_ATPase is almost always more negative than Erev_ANT. Here we review the conditions that define the boundaries of the "B space". Emphasis is placed on the role of matrix substrate-level phosphorylation, because during metabolic compromise this mechanism could maintain mitochondrial membrane potential and prevent the influx of cytosolic ATP destined for hydrolysis by the reversed F(0) -F(1) ATP synthase.
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64
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Offermann S, Okita TW, Edwards GE. Resolving the compartmentation and function of C4 photosynthesis in the single-cell C4 species Bienertia sinuspersici. PLANT PHYSIOLOGY 2011; 155:1612-28. [PMID: 21263039 PMCID: PMC3091117 DOI: 10.1104/pp.110.170381] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 01/15/2011] [Indexed: 05/17/2023]
Abstract
Bienertia sinuspersici is a land plant known to perform C(4) photosynthesis through the location of dimorphic chloroplasts in separate cytoplasmic domains within a single photosynthetic cell. A protocol was developed with isolated protoplasts to obtain peripheral chloroplasts (P-CP), a central compartment (CC), and chloroplasts from the CC (C-CP) to study the subcellular localization of photosynthetic functions. Analyses of these preparations established intracellular compartmentation of processes to support a NAD-malic enzyme (ME)-type C(4) cycle. Western-blot analyses indicated that the CC has Rubisco from the C(3) cycle, the C(4) decarboxylase NAD-ME, a mitochondrial isoform of aspartate aminotransferase, and photorespiratory markers, while the C-CP and P-CP have high levels of Rubisco and pyruvate, Pidikinase, respectively. Other enzymes for supporting a NAD-ME cycle via an aspartate-alanine shuttle, carbonic anhydrase, phosophoenolpyruvate carboxylase, alanine, and an isoform of aspartate aminotransferase are localized in the cytosol. Functional characterization by photosynthetic oxygen evolution revealed that only the C-CP have a fully operational C(3) cycle, while both chloroplast types have the capacity to photoreduce 3-phosphoglycerate. The P-CP were enriched in a putative pyruvate transporter and showed light-dependent conversion of pyruvate to phosphoenolpyruvate. There is a larger investment in chloroplasts in the central domain than in the peripheral domain (6-fold more chloroplasts and 4-fold more chlorophyll). The implications of this uneven distribution for the energetics of the C(4) and C(3) cycles are discussed. The results indicate that peripheral and central compartment chloroplasts in the single-cell C(4) species B. sinuspersici function analogous to mesophyll and bundle sheath chloroplasts of Kranz-type C(4) species.
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Affiliation(s)
| | | | - Gerald E. Edwards
- School of Biological Sciences (S.O., G.E.E.) and Institute of Biological Chemistry (T.W.O.), Washington State University, Pullman, Washington 99164
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65
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Abstract
AbstractThe rotary ATPase family of membrane protein complexes may have only three members, but each one plays a fundamental role in biological energy conversion. The F1Fo-ATPase (F-ATPase) couples ATP synthesis to the electrochemical membrane potential in bacteria, mitochondria and chloroplasts, while the vacuolar H+-ATPase (V-ATPase) operates as an ATP-driven proton pump in eukaryotic membranes. In different species of archaea and bacteria, the A1Ao-ATPase (A-ATPase) can function as either an ATP synthase or an ion pump. All three of these multi-subunit complexes are rotary molecular motors, sharing a fundamentally similar mechanism in which rotational movement drives the energy conversion process. By analogy to macroscopic systems, individual subunits can be assigned to rotor, axle or stator functions. Recently, three-dimensional reconstructions from electron microscopy and single particle image processing have led to a significant step forward in understanding of the overall architecture of all three forms of these complexes and have allowed the organisation of subunits within the rotor and stator parts of the motors to be more clearly mapped out. This review describes the emerging consensus regarding the organisation of the rotor and stator components of V-, A- and F-ATPases, examining core similarities that point to a common evolutionary origin, and highlighting key differences. In particular, it discusses how newly revealed variation in the complexity of the inter-domain connections may impact on the mechanics and regulation of these molecular machines.
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66
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Börsch M, Wrachtrup J. Improving FRET‐Based Monitoring of Single Chemomechanical Rotary Motors at Work. Chemphyschem 2011; 12:542-53. [DOI: 10.1002/cphc.201000702] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Revised: 12/12/2010] [Indexed: 11/07/2022]
Affiliation(s)
- Michael Börsch
- 3rd Institute of Physics and Stuttgart Research Center SCOPE, University of Stuttgart, Pfaffenwaldring 57, Fax: (+49) 711‐685‐65281
| | - Jörg Wrachtrup
- 3rd Institute of Physics and Stuttgart Research Center SCOPE, University of Stuttgart, Pfaffenwaldring 57, Fax: (+49) 711‐685‐65281
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67
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Dong H, Nie R, Hou X, Wang P, Yue J, Jiang L. Assembly of F0F1-ATPase into solid state nanoporous membrane. Chem Commun (Camb) 2011; 47:3102-4. [DOI: 10.1039/c0cc05107a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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68
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Kramer DM, Evans JR. The importance of energy balance in improving photosynthetic productivity. PLANT PHYSIOLOGY 2011; 155:70-8. [PMID: 21078862 PMCID: PMC3075755 DOI: 10.1104/pp.110.166652] [Citation(s) in RCA: 319] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 11/10/2010] [Indexed: 05/18/2023]
Affiliation(s)
- David M Kramer
- Biochemistry and Molecular Biology and Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
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69
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Amthor JS. From sunlight to phytomass: on the potential efficiency of converting solar radiation to phyto-energy. THE NEW PHYTOLOGIST 2010; 188:939-59. [PMID: 20977480 DOI: 10.1111/j.1469-8137.2010.03505.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The relationship between solar radiation capture and potential plant growth is of theoretical and practical importance. The key processes constraining the transduction of solar radiation into phyto-energy (i.e. free energy in phytomass) were reviewed to estimate potential solar-energy-use efficiency. Specifically, the out-put:input stoichiometries of photosynthesis and photorespiration in C(3) and C(4) systems, mobilization and translocation of photosynthate, and biosynthesis of major plant biochemical constituents were evaluated. The maintenance requirement, an area of important uncertainty, was also considered. For a hypothetical C(3) grain crop with a full canopy at 30°C and 350 ppm atmospheric [CO(2) ], theoretically potential efficiencies (based on extant plant metabolic reactions and pathways) were estimated at c. 0.041 J J(-1) incident total solar radiation, and c. 0.092 J J(-1) absorbed photosynthetically active radiation (PAR). At 20°C, the calculated potential efficiencies increased to 0.053 and 0.118 J J(-1) (incident total radiation and absorbed PAR, respectively). Estimates for a hypothetical C(4) cereal were c. 0.051 and c. 0.114 J J(-1), respectively. These values, which cannot be considered as precise, are less than some previous estimates, and the reasons for the differences are considered. Field-based data indicate that exceptional crops may attain a significant fraction of potential efficiency.
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Affiliation(s)
- Jeffrey S Amthor
- Faculty of Agriculture, Food and Natural Resources (C81), University of Sydney, NSW 2006, Australia.
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70
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Bailleul B, Cardol P, Breyton C, Finazzi G. Electrochromism: a useful probe to study algal photosynthesis. PHOTOSYNTHESIS RESEARCH 2010; 106:179-89. [PMID: 20632109 DOI: 10.1007/s11120-010-9579-z] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Accepted: 06/23/2010] [Indexed: 05/07/2023]
Abstract
In photosynthesis, electron transfer along the photosynthetic chain results in a vectorial transfer of protons from the stroma to the lumenal space of the thylakoids. This promotes the generation of an electrochemical proton gradient (Δμ(H)(+)), which comprises a gradient of electric potential (ΔΨ) and of proton concentration (ΔpH). The Δμ(H)(+) has a central role in the photosynthetic process, providing the energy source for ATP synthesis. It is also involved in many regulatory mechanisms. The ΔpH modulates the rate of electron transfer and triggers deexcitation of excess energy within the light harvesting complexes. The ΔΨ is required for metabolite and protein transport across the membranes. Its presence also induces a shift in the absorption spectra of some photosynthetic pigments, resulting in the so-called ElectroChromic Shift (ECS). In this review, we discuss the characteristic features of the ECS, and illustrate possible applications for the study of photosynthetic processes in vivo.
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Affiliation(s)
- Benjamin Bailleul
- UMR 7141, Centre National de la Recherche Scientifique, Institut de Biologie Physico-Chimique, Université Pierre et Marie Curie, 75005 Paris, France.
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71
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Finazzi G, Moreau H, Bowler C. Genomic insights into photosynthesis in eukaryotic phytoplankton. TRENDS IN PLANT SCIENCE 2010; 15:565-572. [PMID: 20800533 DOI: 10.1016/j.tplants.2010.07.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Revised: 07/21/2010] [Accepted: 07/22/2010] [Indexed: 05/29/2023]
Abstract
The evolution of photosynthesis completely altered the biogeochemistry of our planet and permitted the evolution of more complex multicellular organisms. Curiously, terrestrial photosynthesis is carried out largely by green algae and their descendents the higher plants, whereas in the ocean the most abundant photosynthetic eukaryotes are microscopic and have red algal affiliations. Although primary productivity is approximately equal between the land and the ocean, the marine microbes represent less than 1% of the photosynthetic biomass found on land. This review focuses on this highly successful and diverse group of organisms collectively known as phytoplankton and reviews how insights from whole genome analyses have improved our understanding of the novel innovations employed by them to maximize photosynthetic efficiency in variable light environments.
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Affiliation(s)
- Giovanni Finazzi
- Laboratoire de Physiologie Vegetale et Cellulaire, UMR 5168 Centre National de la Recherche Scientifique/Commissariat à l'énergie atomique et aux énergies alternatives/Université Joseph Fourier, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble, France
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Abstract
F(o)F(1)-ATPase is an amazing molecular rotary motor at the nanoscale. Single molecule technologies have contributed much to the understanding of the motor. For example, fluorescence imaging and spectroscopy revealed the physical rotation of isolated F(1) and F(o), or F(o)F(1) holoenzyme. Magnetic tweezers were employed to manipulate the ATP synthesis/hydrolysis in F(1), and proton translation in F(o). Here, we briefly review our recent works including a systematic kinetics study of the holoenzyme, the mechanochemical coupling mechanism, reconstituting the delta-free F(o)F(1)-ATPase, direct observation of F(o) rotation at single molecule level and activity regulation through external links on the stator.
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Affiliation(s)
- Yao-Gen Shu
- Institute of Theoretical Physics, CAS, Beijing, 100190, China.
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74
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Kagawa Y. ATP synthase: from single molecule to human bioenergetics. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2010; 86:667-93. [PMID: 20689227 PMCID: PMC3066536 DOI: 10.2183/pjab.86.667] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 04/30/2010] [Indexed: 05/20/2023]
Abstract
ATP synthase (F(o)F(1)) consists of an ATP-driven motor (F(1)) and a H(+)-driven motor (F(o)), which rotate in opposite directions. F(o)F(1) reconstituted into a lipid membrane is capable of ATP synthesis driven by H(+) flux. As the basic structures of F(1) (alpha(3)beta(3)gammadeltaepsilon) and F(o) (ab(2)c(10)) are ubiquitous, stable thermophilic F(o)F(1) (TF(o)F(1)) has been used to elucidate molecular mechanisms, while human F(1)F(o) (HF(1)F(o)) has been used to study biomedical significance. Among F(1)s, only thermophilic F(1) (TF(1)) can be analyzed simultaneously by reconstitution, crystallography, mutagenesis and nanotechnology for torque-driven ATP synthesis using elastic coupling mechanisms. In contrast to the single operon of TF(o)F(1), HF(o)F(1) is encoded by both nuclear DNA with introns and mitochondrial DNA. The regulatory mechanism, tissue specificity and physiopathology of HF(o)F(1) were elucidated by proteomics, RNA interference, cytoplasts and transgenic mice. The ATP synthesized daily by HF(o)F(1) is in the order of tens of kilograms, and is primarily controlled by the brain in response to fluctuations in activity.
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75
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Cheng J, Zhang XA, Shu YG, Yue JC. F0F1-ATPase activity regulated by external links on beta subunits. Biochem Biophys Res Commun 2009; 391:182-6. [PMID: 19900413 DOI: 10.1016/j.bbrc.2009.11.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Accepted: 11/05/2009] [Indexed: 10/20/2022]
Abstract
F(o)F(1)-ATPase activity is regulated by external links on beta subunits with different molecular weight. It is inhibited when anti-beta subunit antibody, streptavidin and H9 antibody link on the beta subunits successively, but is activated when virus was binded. Western blotting indicated that the employed anti-beta antibody target was on the non-catalytic site of the beta subunit. Furthermore, an ESR study of spin-labeled ATP (SL-ATP) showed that the affinity of ATP to the holoenzyme increases with increasing external links on the beta subunits. This simple regulation method may have great potential in the design of rapid, free labeled, sensitive and selective biosensors.
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Affiliation(s)
- Jie Cheng
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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76
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Yin X, Struik PC. Theoretical reconsiderations when estimating the mesophyll conductance to CO(2) diffusion in leaves of C(3) plants by analysis of combined gas exchange and chlorophyll fluorescence measurements. PLANT, CELL & ENVIRONMENT 2009; 32:1513-1524. [PMID: 19558403 DOI: 10.1111/j.1365-3040.2009.02016.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Existing methods to estimate the mesophyll conductance to CO(2) diffusion (g(m)) are often based on combined gas exchange and chlorophyll fluorescence measurements. However, estimations of average g(m) by these methods are often unreliable either because the range of usable data is too narrow or because the estimations are very sensitive to measurement errors. We describe three method variants to estimate g(m), for which a wider range of data are usable. They use curve-fitting techniques, which minimise the sum of squared model deviations from the data for A (CO(2) assimilation rate) or for J (linear electron transport rate). Like the existing approaches, they are all based on common physiological principles assuming that electron transport limits A. The proposed variants were far less sensitive than the existing approaches to 'measurement noise' either created randomly in the generated data set or inevitably existing in real data sets. Yet, the estimates of g(m) from the three variants differed by approximately 15%. Moreover, for each variant, a stoichiometric uncertainty in linear electron transport-limited photosynthesis can cause another 15% difference. Any estimation of g(m) using gas exchange and chlorophyll fluorescence measurements should be considered with caution, especially when g(m) is high.
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Affiliation(s)
- Xinyou Yin
- Centre for Crop Systems Analysis, Department of Plant Sciences, Wageningen University, 6700 AK Wageningen, the Netherlands
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77
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Petroutsos D, Terauchi AM, Busch A, Hirschmann I, Merchant SS, Finazzi G, Hippler M. PGRL1 participates in iron-induced remodeling of the photosynthetic apparatus and in energy metabolism in Chlamydomonas reinhardtii. J Biol Chem 2009; 284:32770-81. [PMID: 19783661 DOI: 10.1074/jbc.m109.050468] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
PGRL1 RNA and protein levels are increased in iron-deficient Chlamydomonas reinhardtii cells. In an RNAi strain, which accumulates lower PGRL1 levels in both iron-replete and -starved conditions, the photosynthetic electron transfer rate is decreased, respiratory capacity in iron-sufficient conditions is increased, and the efficiency of cyclic electron transfer under iron-deprivation is diminished. Pgrl1-kd cells exhibit iron deficiency symptoms at higher iron concentrations than wild-type cells, although the cells are not more depleted in cellular iron relative to wild-type cells as measured by mass spectrometry. Thiol-trapping experiments indicate iron-dependent and redox-induced conformational changes in PGRL1 that may provide a link between iron metabolism and the partitioning of photosynthetic electron transfer between linear and cyclic flow. We propose, therefore, that PGRL1 in C. reinhardtii may possess a dual function in the chloroplast; that is, iron sensing and modulation of electron transfer.
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Affiliation(s)
- Dimitris Petroutsos
- Institute of Plant Biochemistry and Biotechnology, University of Münster, Hindenburgplatz 55, 48143 Münster, Germany
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78
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Emergence of Animals from Heat Engines – Part 1. Before the Snowball Earths. ENTROPY 2009. [DOI: 10.3390/e11030463] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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79
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Impaired respiration discloses the physiological significance of state transitions in Chlamydomonas. Proc Natl Acad Sci U S A 2009; 106:15979-84. [PMID: 19805237 DOI: 10.1073/pnas.0908111106] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
State transitions correspond to a major regulation process for photosynthesis, whereby chlorophyll protein complexes responsible for light harvesting migrate between photosystem II and photosystem I in response to changes in the redox poise of the intersystem electron carriers. Here we disclose their physiological significance in Chlamydomonas reinhardtii using a genetic approach. Using single and double mutants defective for state transitions and/or mitochondrial respiration, we show that photosynthetic growth, and therefore biomass production, critically depends on state transitions in respiratory-defective conditions. When extra ATP cannot be provided by respiration, enhanced photosystem I turnover elicited by transition to state 2 is required for photosynthetic activity. Concomitant impairment of state transitions and respiration decreases the overall yield of photosynthesis, ultimately leading to reduced fitness. We thus provide experimental evidence that the combined energetic contributions of state transitions and respiration are required for efficient carbon assimilation in this alga.
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80
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36 degrees step size of proton-driven c-ring rotation in FoF1-ATP synthase. EMBO J 2009; 28:2689-96. [PMID: 19644443 DOI: 10.1038/emboj.2009.213] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Accepted: 06/29/2009] [Indexed: 11/09/2022] Open
Abstract
Synthesis of adenosine triphosphate ATP, the 'biological energy currency', is accomplished by F(o)F(1)-ATP synthase. In the plasma membrane of Escherichia coli, proton-driven rotation of a ring of 10 c subunits in the F(o) motor powers catalysis in the F(1) motor. Although F(1) uses 120 degrees stepping during ATP synthesis, models of F(o) predict either an incremental rotation of c subunits in 36 degrees steps or larger step sizes comprising several fast substeps. Using single-molecule fluorescence resonance energy transfer, we provide the first experimental determination of a 36 degrees sequential stepping mode of the c-ring during ATP synthesis.
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81
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von Ballmoos C, Wiedenmann A, Dimroth P. Essentials for ATP synthesis by F1F0 ATP synthases. Annu Rev Biochem 2009; 78:649-72. [PMID: 19489730 DOI: 10.1146/annurev.biochem.78.081307.104803] [Citation(s) in RCA: 237] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The majority of cellular energy in the form of adenosine triphosphate (ATP) is synthesized by the ubiquitous F(1)F(0) ATP synthase. Power for ATP synthesis derives from an electrochemical proton (or Na(+)) gradient, which drives rotation of membranous F(0) motor components. Efficient rotation not only requires a significant driving force (DeltamuH(+)), consisting of membrane potential (Deltapsi) and proton concentration gradient (DeltapH), but also a high proton concentration at the source P side. In vivo this is maintained by dynamic proton movements across and along the surface of the membrane. The torque-generating unit consists of the interface of the rotating c ring and the stator a subunit. Ion translocation through this unit involves a sophisticated interplay between the c-ring binding sites, the stator arginine, and the coupling ions on both sides of the membrane. c-ring rotation is transmitted to the eccentric shaft gamma-subunit to elicit conformational changes in the catalytic sites of F(1), leading to ATP synthesis.
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Affiliation(s)
- Christoph von Ballmoos
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden.
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82
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Junge W, Sielaff H, Engelbrecht S. Torque generation and elastic power transmission in the rotary F(O)F(1)-ATPase. Nature 2009; 459:364-70. [PMID: 19458712 DOI: 10.1038/nature08145] [Citation(s) in RCA: 272] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Adenosine triphosphate (ATP), the universal fuel of the cell, is synthesized from adenosine diphosphate (ADP) and inorganic phosphate (P(i)) by 'ATP synthase' (F(O)F(1)-ATPase). During respiration or photosynthesis, an electrochemical potential difference of protons is set up across the respective membranes. This powers the enzyme's electrical rotary nanomotor (F(O)), which drives the chemical nanomotor (F(1)) by elastic mechanical-power transmission, producing ATP with high kinetic efficiency. Attempts to understand in detail the mechanisms of torque generation in this simple and robust system have been both aided and complicated by a wealth of sometimes conflicting data.
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Affiliation(s)
- Wolfgang Junge
- Department of Biophysics, University of Osnabrück, Barbarastrasse 11, 49076 Osnabrück, Germany.
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83
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Respiration of Escherichia coli can be fully uncoupled via the nonelectrogenic terminal cytochrome bd-II oxidase. J Bacteriol 2009; 191:5510-7. [PMID: 19542282 DOI: 10.1128/jb.00562-09] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The respiratory chain of Escherichia coli is usually considered a device to conserve energy via the generation of a proton motive force, which subsequently may drive ATP synthesis by the ATP synthetase. It is known that in this system a fixed amount of ATP per oxygen molecule reduced (P/O ratio) is not synthesized due to alternative NADH dehydrogenases and terminal oxidases with different proton pumping stoichiometries. Here we show that P/O ratios can vary much more than previously thought. First, we show that in wild-type E. coli cytochrome bo, cytochrome bd-I, and cytochrome bd-II are the major terminal oxidases; deletion of all of the genes encoding these enzymes results in a fermentative phenotype in the presence of oxygen. Second, we provide evidence that the electron flux through cytochrome bd-II oxidase is significant but does not contribute to the generation of a proton motive force. The kinetics support the view that this system is as an energy-independent system gives the cell metabolic flexibility by uncoupling catabolism from ATP synthesis under non-steady-state conditions. The nonelectrogenic nature of cytochrome bd-II oxidase implies that the respiratory chain can function in a fully uncoupled mode such that ATP synthesis occurs solely by substrate level phosphorylation. As a consequence, the yield with a carbon and energy source can vary five- to sevenfold depending on the electron flux distribution in the respiratory chain. A full understanding and control of this distribution open new avenues for optimization of biotechnological processes.
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84
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Concentration gradient effects of sodium and lithium ions and deuterium isotope effects on the activities of H+-ATP synthase from chloroplasts. Biophys J 2009; 96:2479-89. [PMID: 19289072 DOI: 10.1016/j.bpj.2008.12.3910] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2008] [Revised: 11/27/2008] [Accepted: 12/05/2008] [Indexed: 11/22/2022] Open
Abstract
We explored the concentration gradient effects of the sodium and lithium ions and the deuterium isotope's effects on the activities of H(+)-ATP synthase from chloroplasts (CF(0)F(1)). We found that the sodium concentration gradient can drive the ATP synthesis reaction of CF(0)F(1). In contrast, the lithium ion can be an efficient enzyme-inhibitor by blocking the entrance channel of the ion translocation pathway in CF(0). In the presence of sodium or lithium ions and with the application of a membrane potential, unexpected enzyme behaviors of CF(0)F(1) were evident. To account for these observations, we propose that both of the sodium and lithium ions could undergo localized hydrolysis reactions in the chemical environment of the ion channel of CF(0). The protons generated locally could proceed to complete the ion translocation process in the ATP synthesis reaction of CF(0)F(1). Experimental and theoretical deuterium isotope effects of the localized hydrolysis on the activities of CF(0)F(1), and the energetics of these related reactions, support this proposed mechanism. Our experimental observations could be understood in the framework of the well-established ion translocation models for the H(+)-ATP synthase from Escherichia coli, and the Na(+)-ATP synthase from Propionigenium modestum and Ilyobacter tartaricus.
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85
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Raven JA. Functional evolution of photochemical energy transformations in oxygen-producing organisms. FUNCTIONAL PLANT BIOLOGY : FPB 2009; 36:505-515. [PMID: 32688665 DOI: 10.1071/fp09087] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 04/21/2009] [Indexed: 05/21/2023]
Abstract
Chlorophyll a is the photochemical agent accounting for most oxygenic photosynthesis, that is, over 99.9% of photosynthetic primary activity on Earth. The spectral and energetic properties of chlorophyll a can, at least in part, be rationalised in terms of the solar spectral output and the energetics of oxygen production and carbon dioxide reduction with two photochemical reactions. The long wavelength limit on in vivo chlorophyll a absorption is probably close to the energetic limit: longer wavelengths could not support a high rate and efficiency of oxygenic photosynthesis. Retinal, a β-carotene derivative that is the chromophore of rhodopsin, acts not only as a sensory pigment, but also as an ion-pumping photochemical transducer. Both sensory and energy-transforming rhodopsins occur in oxygenic phototrophs, although the extent of expression and the function of the latter are not well understood.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at SCRI, Invergowrie, Dundee DD2 5DA, UK. Email
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86
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Allen DK, Ohlrogge JB, Shachar-Hill Y. The role of light in soybean seed filling metabolism. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 58:220-34. [PMID: 19077167 DOI: 10.1111/j.1365-313x.2008.03771.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Soybean (Glycine max) yields high levels of both protein and oil, making it one of the most versatile and important crops in the world. Light has been implicated in the physiology of developing green seeds including soybeans but its roles are not quantitatively understood. We have determined the light levels reaching growing soybean embryos under field conditions and report detailed redox and energy balance analyses for them. Direct flux measurements and labeling patterns for multiple labeling experiments including [U-(13)C(6)]-glucose, [U-(13)C(5)]-glutamine, the combination of [U-(14)C(12)]-sucrose + [U-(14)C(6)]-glucose + [U-(14)C(5)]-glutamine + [U-(14)C(4)]-asparagine, or (14)CO2 labeling were performed at different light levels to give further insight into green embryo metabolism during seed filling and to develop and validate a flux map. Labeling patterns (protein amino acids, triacylglycerol fatty acids, starch, cell wall, protein glycan monomers, organic acids), uptake fluxes (glutamine, asparagine, sucrose, glucose), fluxes to biomass (protein amino acids, oil), and respiratory fluxes (CO2, O2) were established by a combination of gas chromatography-mass spectrometry, (13)C- and (1)H-NMR, scintillation counting, HPLC, gas chromatography-flame ionization detection, C:N and amino acid analyses, and infrared gas analysis, yielding over 750 measurements of metabolism. Our results show: (i) that developing soybeans receive low but significant light levels that influence growth and metabolism; (ii) a role for light in generating ATP but not net reductant during seed filling; (iii) that flux through Rubisco contributes to carbon conversion efficiency through generation of 3-phosphoglycerate; and (iv) a larger contribution of amino acid carbon to fatty acid synthesis than in other oilseeds analyzed to date.
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Affiliation(s)
- Doug K Allen
- Michigan State University, Plant Biology Department, East Lansing, MI 48824, USA.
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87
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Seelert H, Dani DN, Dante S, Hauss T, Krause F, Schäfer E, Frenzel M, Poetsch A, Rexroth S, Schwassmann HJ, Suhai T, Vonck J, Dencher NA. From protons to OXPHOS supercomplexes and Alzheimer's disease: structure-dynamics-function relationships of energy-transducing membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:657-71. [PMID: 19281792 DOI: 10.1016/j.bbabio.2009.02.028] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Revised: 02/20/2009] [Accepted: 02/20/2009] [Indexed: 11/29/2022]
Abstract
By the elucidation of high-resolution structures the view of the bioenergetic processes has become more precise. But in the face of these fundamental advances, many problems are still unresolved. We have examined a variety of aspects of energy-transducing membranes from large protein complexes down to the level of protons and functional relevant picosecond protein dynamics. Based on the central role of the ATP synthase for supplying the biological fuel ATP, one main emphasis was put on this protein complex from both chloroplast and mitochondria. In particular the stoichiometry of protons required for the synthesis of one ATP molecule and the supramolecular organisation of ATP synthases were examined. Since formation of supercomplexes also concerns other complexes of the respiratory chain, our work was directed to unravel this kind of organisation, e.g. of the OXPHOS supercomplex I(1)III(2)IV(1), in terms of structure and function. Not only the large protein complexes or supercomplexes work as key players for biological energy conversion, but also small components as quinones which facilitate the transfer of electrons and protons. Therefore, their location in the membrane profile was determined by neutron diffraction. Physico-chemical features of the path of protons from the generators of the electrochemical gradient to the ATP synthase, as well as of their interaction with the membrane surface, could be elucidated by time-resolved absorption spectroscopy in combination with optical pH indicators. Diseases such as Alzheimer's dementia (AD) are triggered by perturbation of membranes and bioenergetics as demonstrated by our neutron scattering studies.
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Affiliation(s)
- H Seelert
- Department of Chemistry, Technische Universität Darmstadt, Petersenstrasse 22, D-64287 Darmstadt, Germany.
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88
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Constant c10 ring stoichiometry in the Escherichia coli ATP synthase analyzed by cross-linking. J Bacteriol 2009; 191:2400-4. [PMID: 19181809 DOI: 10.1128/jb.01390-08] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The subunit c stoichiometry of Escherichia coli ATP synthase was studied by intermolecular cross-linking via oxidation of bi-cysteine-substituted subunit c (cA21C/cM65C). Independent of the carbon source used for growth and independent of the presence of other FoF1 subunits, an equal pattern of cross-link formation stopping at the formation of decamers was obtained.
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89
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Kocherginsky N. Acidic lipids, H(+)-ATPases, and mechanism of oxidative phosphorylation. Physico-chemical ideas 30 years after P. Mitchell's Nobel Prize award. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 99:20-41. [PMID: 19049812 DOI: 10.1016/j.pbiomolbio.2008.10.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Peter D. Mitchell, who was awarded the Nobel Prize in Chemistry 30 years ago, in 1978, formulated the chemiosmotic theory of oxidative phosphorylation. This review initially analyzes the major aspects of this theory, its unresolved problems, and its modifications. A new physico-chemical mechanism of energy transformation and coupling of oxidation and phosphorylation is then suggested based on recent concepts regarding proteins, including ATPases that work as molecular motors, and acidic lipids that act as hydrogen ion (H(+)) carriers. According to this proposed mechanism, the chemical energy of a redox substrate is transformed into nonequilibrium states of electron-transporting chain (ETC) coupling proteins. This leads to nonequilibrium pumping of H(+) into the membrane. An acidic lipid, cardiolipin, binds with this H(+) and carries it to the ATP-synthase along the membrane surface. This transport generates gradients of surface tension or electric field along the membrane surface. Hydrodynamic effects on a nanolevel lead to rotation of ATP-synthase and finally to the release of ATP into aqueous solution. This model also explains the generation of a transmembrane protonmotive force that is used for regulation of transmembrane transport, but is not necessary for the coupling of electron transport and ATP synthesis.
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90
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Shu YG, Lai PY. Systematic Kinetics Study of FoF1-ATPase: Analytic Results and Comparison with Experiments. J Phys Chem B 2008; 112:13453-9. [DOI: 10.1021/jp8052696] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yao-Gen Shu
- Department of Physics, Graduate Institute of Biophysics and Center for Complex Systems, National Central University, Chung-Li, Taiwan 320, R. O. C., and Institute of Theoretical Physics, The Chinese Academy of Sciences, P.O. Box 2735, Beijing 100080, China
| | - Pik-Yin Lai
- Department of Physics, Graduate Institute of Biophysics and Center for Complex Systems, National Central University, Chung-Li, Taiwan 320, R. O. C., and Institute of Theoretical Physics, The Chinese Academy of Sciences, P.O. Box 2735, Beijing 100080, China
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