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Quarato G, Piccoli C, Scrima R, Capitanio N. Variation of flux control coefficient of cytochrome c oxidase and of the other respiratory chain complexes at different values of protonmotive force occurs by a threshold mechanism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1114-24. [PMID: 21565165 DOI: 10.1016/j.bbabio.2011.04.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 04/10/2011] [Accepted: 04/13/2011] [Indexed: 11/17/2022]
Abstract
The metabolic control analysis was applied to digitonin-permeabilized HepG2 cell line to assess the flux control exerted by cytochrome c oxidase on the mitochondrial respiration. Experimental conditions eliciting different energy/respiratory states in mitochondria were settled. The results obtained show that the mitochondrial electrochemical potential accompanies a depressing effect on the control coefficient exhibited by the cytochrome c oxidase. Both the components of the protonmotive force, i.e. the voltage (ΔΨ(m)) and the proton (ΔpH(m)) gradient, displayed a similar effect. Quantitative estimation of the ΔΨ(m) unveiled that the voltage-dependent effect on the control coefficient of cytochrome c oxidase takes place sharply in a narrow range of membrane potential from 170-180 to 200-210mV consistent with the physiologic transition from state 3 to state 4 of respiration. Extension of the metabolic flux control analysis to the NADH dehydrogenase and bc(1) complexes of the mitochondrial respiratory chain resulted in a similar effect. A mechanistic model is put forward whereby the respiratory chain complexes are proposed to exist in a voltage-mediated threshold-controlled dynamic equilibrium between supercomplexed and isolated states.
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2
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Leaf C3 Photosynthesis in silico: Integrated Carbon/Nitrogen Metabolism. PHOTOSYNTHESIS IN SILICO 2009. [DOI: 10.1007/978-1-4020-9237-4_13] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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3
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Abstract
Chemical transformations, like osmotic translocations, are transport processes when looked at in detail. In chemiosmotic systems, the pathways of specific ligand conduction are spatially orientated through osmoenzymes and porters in which the actions of chemical group, electron and solute transfer occur as vectorial (or higher tensorial order) diffusion processes down gradients of total potential energy that represent real spatially directed fields of force. Thus, it has been possible to describe classical bag-of-enzymes biochemistry as well as membrane biochemistry in terms of transport. But it would not have been possible to explain biological transport in terms of classical transformational biochemistry or chemistry. The recognition of this conceptual asymmetry in favour of transport has seemed to be upsetting to some biochemists and chemists; and they have resisted the shift towards thinking primarily in terms of the vectorial forces and co-linear displacements of ligands in place of their much less informative scalar products that correspond to the conventional scalar energies. Nevertheless, considerable progress has been made in establishing vectorial metabolism and osmochemistry as acceptable biochemical disciplines embracing transport and metabolism, and bioenergetics has been fundamentally transformed as a result.
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Affiliation(s)
- Peter D Mitchell
- Glynn Research Institute, PL30 4AU , Bodmin, Cornwall, United Kingdom
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4
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Kuznetsova SS, Azarkina NV, Vygodina TV, Siletsky SA, Konstantinov AA. Zinc ions as cytochrome C oxidase inhibitors: two sites of action. BIOCHEMISTRY (MOSCOW) 2005; 70:128-36. [PMID: 15807649 DOI: 10.1007/s10541-005-0091-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Zinc ions are shown to be an efficient inhibitor of mitochondrial cytochrome c oxidase activity, both in the solubilized and the liposome-reconstituted enzyme. The effect of zinc is biphasic. First there occurs rapid interaction of zinc with the enzyme at a site exposed to the aqueous phase corresponding to the mitochondrial matrix. This interaction is fully reversed by EDTA and results in a partial inhibition of the enzyme activity (50-90%, depending on preparation) with an effective K(i) of approximately 10 microM. The rapid effect of zinc is observed with the solubilized enzyme, it vanishes upon incorporation of cytochrome oxidase in liposomes, and it re-appears when proteoliposomes are supplied with alamethicin that makes the membrane permeable to low molecular weight substances. Zinc presumably blocks the entrance of the D-protonic channel opening into the inner aqueous phase. Second, zinc interacts slowly (tens of minutes, hours) with a site of cytochrome oxidase accessible from the outer aqueous phase bringing about complete inhibition of the enzymatic activity. The slow phase is characterized by high affinity of the inhibitor for the enzyme: full inhibition can be achieved upon incubation of the solubilized oxidase for 24 h with zinc concentration as low as 2 microM. The rate of zinc inhibitory action in the slow phase is proportional to Zn(2+) concentration. The slow interaction of zinc with the outer surface of liposome-reconstituted cytochrome oxidase is observed only with the enzyme turning over or in the presence of weak reductants, whereas incubation of zinc with the fully oxidized proteoliposomes does not induce the inhibition. It is shown that zinc ions added to cytochrome oxidase proteoliposomes from the outside inhibit specifically the slow electrogenic phase of proton transfer, coupled to a transition of cytochrome oxidase from the oxo-ferryl to the oxidized state (the F --> O step corresponding to transfer of the 4th electron in the catalytic cycle).
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Affiliation(s)
- S S Kuznetsova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Vorobjevy Gory, Moscow 119992, Russia
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Joët T, Cournac L, Horvath EM, Medgyesy P, Peltier G. Increased sensitivity of photosynthesis to antimycin A induced by inactivation of the chloroplast ndhB gene. Evidence for a participation of the NADH-dehydrogenase complex to cyclic electron flow around photosystem I. PLANT PHYSIOLOGY 2001; 125:1919-29. [PMID: 11299371 PMCID: PMC88847 DOI: 10.1104/pp.125.4.1919] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2000] [Revised: 10/05/2000] [Accepted: 12/08/2000] [Indexed: 05/18/2023]
Abstract
Tobacco (Nicotiana tabacum var Petit Havana) ndhB-inactivated mutants (ndhB-) obtained by plastid transformation (E.M. Horvath, S.O. Peter, T. Joët, D. Rumeau, L. Cournac, G.V. Horvath, T.A. Kavanagh, C. Schäfer, G. Peltier, P. MedgyesyHorvath [2000] Plant Physiol 123: 1337-1350) were used to study the role of the NADH-dehydrogenase complex (NDH) during photosynthesis and particularly the involvement of this complex in cyclic electron flow around photosystem I (PSI). Photosynthetic activity was determined on leaf discs by measuring CO2 exchange and chlorophyll fluorescence quenchings during a dark-to-light transition. In the absence of treatment, both non-photochemical and photochemical fluorescence quenchings were similar in ndhB- and wild type (WT). When leaf discs were treated with 5 microM antimycin A, an inhibitor of cyclic electron flow around PSI, both quenchings were strongly affected. At steady state, maximum photosynthetic electron transport activity was inhibited by 20% in WT and by 50% in ndhB-. Under non-photorespiratory conditions (2% O2, 2,500 microL x L(-1) CO2), antimycin A had no effect on photosynthetic activity of WT, whereas a 30% inhibition was observed both on quantum yield of photosynthesis assayed by chlorophyll fluorescence and on CO2 assimilation in ndhB-. The effect of antimycin A on ndhB- could not be mimicked by myxothiazol, an inhibitor of the mitochondrial cytochrome bc1 complex, therefore showing that it is not related to an inhibition of the mitochondrial electron transport chain but rather to an inhibition of cyclic electron flow around PSI. We conclude to the existence of two different pathways of cyclic electron flow operating around PSI in higher plant chloroplasts. One of these pathways, sensitive to antimycin A, probably involves ferredoxin plastoquinone reductase, whereas the other involves the NDH complex. The absence of visible phenotype in ndhB- plants under normal conditions is explained by the complement of these two pathways in the supply of extra-ATP for photosynthesis.
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Affiliation(s)
- T Joët
- Commissariat à l'Energie Atomique, Cadarache, Laboratoire d'Ecophysiologie de la Photosynthèse, Département d'Ecophysiologie Végétale et Microbiologie, Bât. 161, F-13108 Saint-Paul-lez-Durance, France
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6
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Vos MH, Borisov VB, Liebl U, Martin JL, Konstantinov AA. Femtosecond resolution of ligand-heme interactions in the high-affinity quinol oxidase bd: A di-heme active site? Proc Natl Acad Sci U S A 2000; 97:1554-9. [PMID: 10660685 PMCID: PMC26473 DOI: 10.1073/pnas.030528197] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/1999] [Accepted: 12/06/1999] [Indexed: 11/18/2022] Open
Abstract
Interaction of the two high-spin hemes in the oxygen reduction site of the bd-type quinol oxidase from Escherichia coli has been studied by femtosecond multicolor transient absorption spectroscopy. The previously unidentified Soret band of ferrous heme b(595) was determined to be centered around 440 nm by selective excitation of the fully reduced unliganded or CO-bound cytochrome bd in the alpha-band of heme b(595). The redox state of the b-type hemes strongly affects both the line shape and the kinetics of the absorption changes induced by photodissociation of CO from heme d. In the reduced enzyme, CO photodissociation from heme d perturbs the spectrum of ferrous cytochrome b(595) within a few ps, pointing to a direct interaction between hemes b(595) and d. Whereas in the reduced enzyme no heme d-CO geminate recombination is observed, in the mixed-valence CO-liganded complex with heme b(595) initially oxidized, a significant part of photodissociated CO does not leave the protein and recombines with heme d within a few hundred ps. This caging effect may indicate that ferrous heme b(595) provides a transient binding site for carbon monoxide within one of the routes by which the dissociated ligand leaves the protein. Taken together, the data indicate physical proximity of the hemes d and b(595) and corroborate the possibility of a functional cooperation between the two hemes in the dioxygen-reducing center of cytochrome bd.
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Affiliation(s)
- M H Vos
- Institut National de la Santé et de la Recherche Médicale U451, Laboratoire d'Optique Appliquée, Ecole Polytechnique-Ecole Nationale Supérieure des Techniques Avancées, 91761 Palaiseau Cedex, France.
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7
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Konstantinov AA, Siletsky S, Mitchell D, Kaulen A, Gennis RB. The roles of the two proton input channels in cytochrome c oxidase from Rhodobacter sphaeroides probed by the effects of site-directed mutations on time-resolved electrogenic intraprotein proton transfer. Proc Natl Acad Sci U S A 1997; 94:9085-90. [PMID: 9256439 PMCID: PMC23042 DOI: 10.1073/pnas.94.17.9085] [Citation(s) in RCA: 265] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/1996] [Accepted: 05/28/1997] [Indexed: 02/05/2023] Open
Abstract
The crystal structures of cytochrome c oxidase from both bovine and Paracoccus denitrificans reveal two putative proton input channels that connect the heme-copper center, where dioxygen is reduced, to the internal aqueous phase. In this work we have examined the role of these two channels, looking at the effects of site-directed mutations of residues observed in each of the channels of the cytochrome c oxidase from Rhodobacter sphaeroides. A photoelectric technique was used to monitor the time-resolved electrogenic proton transfer steps associated with the photo-induced reduction of the ferryl-oxo form of heme a3 (Fe4+ = O2-) to the oxidized form (Fe3+OH-). This redox step requires the delivery of a "chemical" H+ to protonate the reduced oxygen atom and is also coupled to proton pumping. It is found that mutations in the K channel (K362M and T359A) have virtually no effect on the ferryl-oxo-to-oxidized (F-to-Ox) transition, although steady-state turnover is severely limited. In contrast, electrogenic proton transfer at this step is strongly suppressed by mutations in the D channel. The results strongly suggest that the functional roles of the two channels are not the separate delivery of chemical or pumped protons, as proposed recently [Iwata, S., Ostermeier, C., Ludwig, B. & Michel, H. (1995) Nature (London) 376, 660-669]. The D channel is likely to be involved in the uptake of both "chemical" and "pumped" protons in the F-to-Ox transition, whereas the K channel is probably idle at this partial reaction and is likely to be used for loading the enzyme with protons at some earlier steps of the catalytic cycle. This conclusion agrees with different redox states of heme a3 in the K362M and E286Q mutants under aerobic steady-state turnover conditions.
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Affiliation(s)
- A A Konstantinov
- A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia
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8
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Bogachev AV, Murtazina RA, Skulachev VP. The Na+/e- stoichiometry of the Na+-motive NADH:quinone oxidoreductase in Vibrio alginolyticus. FEBS Lett 1997; 409:475-7. [PMID: 9224712 DOI: 10.1016/s0014-5793(97)00536-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A method is proposed to estimate the stoichiometries of primary Na+-pumps in intact bacterial cells. It is based on technique when the H+/e- stoichiometry is measured in the presence of protophorous uncoupler and in the absence of penetrating ions other than H+. Under these conditions, the H+ influx discharges membrane potential generated by the Na+ pump so the Na+/e- and H+/e- ratios become equal. Using this approach it is shown that the Na+/e- ratio for the Na+-motive NADH:quinone oxidoreductase of Vibrio alginolyticus is equal to 0.71 +/- 0.06. The Na+/e- stoichiometry appears to be approximately 1, provided that the contribution of the non-coupled NADH:quinone oxidoreductase, which is resistant to low HQNO concentrations, is taken into account.
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Affiliation(s)
- A V Bogachev
- Department of Bioenergetics, A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russia
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9
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Rich PR, Meunier B, Mitchell R, John Moody A. Coupling of charge and proton movement in cytochrome c oxidase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1996. [DOI: 10.1016/0005-2728(96)00055-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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10
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Meunier B, Colson AM, Rich PR. The topology of CuA in relation to the other metal centres in cytochrome-c oxidase of Saccharomyces cerevisiae as determined by analysis of second-site reversions. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1253:13-5. [PMID: 7492593 DOI: 10.1016/0167-4838(95)92373-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Second-site revertants were selected from a respiratory-deficient mutant carrying the mutation D369N located in a loop between helices IX and X close to H376 and H378, the proposed ligands of haem a3 and haem a, respectively. A reversion was observed in subunit II, in the vicinity of the CuA ligands. This same reversion compensates the subunit I deficiency mutation, S140L, assumed to be near H62, the second putative histidine ligand to haem a. These data enable us to propose a three-dimensional topology in which CuA in subunit II is located on top of the Positive-side of subunit I and in proximity to all three of its metal centres.
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Affiliation(s)
- B Meunier
- Glynn Research Institute, Bodmin, Cornwall, UK
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11
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Hoefnagel MH, Wiskich JT, Madgwick SA, Patterson Z, Oettmeier W, Rich PR. New inhibitors of the ubiquinol oxidase of higher plant mitochondria. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 233:531-7. [PMID: 7588798 DOI: 10.1111/j.1432-1033.1995.531_2.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A screen has been performed of possible inhibitors of the ubiquinol oxidase of higher plant mitochondria by assaying their effects on cyanide-insensitive NADH oxidase of mitochondria of Arum maculatum. A number of compounds which have powerful inhibitory effects have been identified. Potent inhibition was found with compounds related to the previously described n-propyl gallate, but with the n-propyl sidechain replaced with alkyl chains of greater hydrophobicity. Titration of a range of partial reactions showed that the inhibitors act specifically on the ubiquinol oxidase. The concentrations of inhibitor required are dependent on the respiratory substrate and on the amount of mitochondria used in the assay. Octyl gallate also proved to be a potent inhibitor of the ubiquinol oxidase in tobacco cell suspensions. A second class of compounds which strongly inhibit cyanide-insensitive NADH oxidation is aurachin C and its analogues. Compounds related to aurachin D are much less effective. Titrations of a range of partial reactions indicate that inhibition is caused by a direct action on the ubiquinol oxidase. However, both types of aurachins also act strongly at the Qi site of the cytochrome bc1 complex, as already known to be the case in other systems, and so they are of more limited value for studies of the ubiquinol oxidase. Titration of the oxidation of NADH via the ubiquinol oxidase in a purified mitochondrial fraction from the spadices of Arum maculatum with octyl gallate gave a half-maximal effect at a concentration of around 6 nM when the protein concentration was 14 micrograms ml-1. A similar titre was obtained with a decyl derivative of aurachin C. This allowed us to estimate an upper limit for the concentration of ubiquinol oxidase in these mitochondria of 0.72 +/- 0.15 nmol mg-1 protein, or a ratio of ubiquinol oxidase/cytochrome oxidase of about 15 +/- 7:1. The measurements also provide a minimal turnover number for the ubiquinol oxidase of 186 +/- 42 electrons.s-1. Titration of the ubiquinol oxidase in soybean cotyledon mitochondria with these compounds gave the concentration of inhibitor required to elicit 50% of the maximum observed effect (I50) values about one order of magnitude higher than those found with Arum mitochondria, and again the values depended on the respiratory substrate. An explanation for the variation in I50 values may be found in terms of differences in oxidase concentrations in the different mitochondrial membranes and in the differences in rate-controlling steps with substrates of different activities.
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Affiliation(s)
- M H Hoefnagel
- Department of Botany, University of Adelaide, Australia
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12
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Papa S, Lorusso M, Capitanio N. Mechanistic and phenomenological features of proton pumps in the respiratory chain of mitochondria. J Bioenerg Biomembr 1994; 26:609-18. [PMID: 7721722 DOI: 10.1007/bf00831535] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023]
Abstract
Various direct, indirect (kinetic and thermodynamic), and combined mechanisms have been proposed to explain the conversion of redox energy into a transmembrane protonmotive force (delta p) by enzymatic complexes of respiratory chains. The conceptual evolution of these models is examined. The characteristics of thermodynamic coupling between redox transitions of electron carriers and scalar proton transfer in cytochrome c oxidase and its possible involvement in proton pumping is discussed. Other aspects dealt with in this paper are: (i) variability of <--H+/e- stoichiometries, in cytochrome c oxidase and cytochrome c reductase and its mechanistic implications; (ii) possible models by which the reduction of dioxygen to water at the binuclear heme-copper center of protonmotive oxidases can be directly involved in proton pumping. Finally a unifying concept for proton pumping by the redox complexes of respiratory chain is presented.
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Affiliation(s)
- S Papa
- Institute of Medical Biochemistry and Chemistry, University of Bari, Italy
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13
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Skulachev VP. Chemiosmotic concept of the membrane bioenergetics: what is already clear and what is still waiting for elucidation? J Bioenerg Biomembr 1994; 26:589-98. [PMID: 7721720 DOI: 10.1007/bf00831533] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The present state of the chemiosmotic concept is reviewed. Special attention is paid to (i) further progress in studies on the Na(+)-coupled energetics and (ii) paradoxical bioenergetic effects when protonic or sodium potentials are utilized outside the coupling membrane (TonB-mediated uphill transports across the outer bacterial membrane). A hypothesis is put forward assuming that the same principle is employed in the bacterial flagellar motor.
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Affiliation(s)
- V P Skulachev
- Department of Bioenergetics, A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russia
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14
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15
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Coppée JY, Tokutake N, Marc D, di Rago JP, Miyoshi H, Colson AM. Analysis of revertants from respiratory deficient mutants within the center N of cytochrome b in Saccharomyces cerevisiae. FEBS Lett 1994; 339:1-6. [PMID: 8313954 DOI: 10.1016/0014-5793(94)80373-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Four modified cytochrome b's carrying mononucleotide substitutions affecting center N residues were analysed. The mutant carrying a G33D change does not incorporate heme into the apocytochrome b and fails to grow on non-fermentable carbon sources. Out of 85 genetically independent revertants derived from this mutant, 82 were true back-mutants restoring the wild type sequence (D33G). The remaining three replaced the aspartic acid by an alanine (D33A) indicating that small size residues are best tolerated at this position which is consistent with the perfect conservation of the G33 during evolution. This glycine may be of crucial importance for helix packing around the hemes. The replacement of methionine at position 221 by lysine (M221K) produced a non-functional cytochrome b [(1993) J. Biol. Chem. 268, 15626-15632]. Non-native revertants replacing the lysine 221 by glutamic acid (K221E) or glutamine (K221Q) expressed a selective resistance to antimycin and antimycin derivatives having a modified dilactone ring moiety. Cytochrome b residues in 33 and in 221 seemed to contribute to the quinone reduction (QN) site of the cytochrome bc1 complex. Possible intramolecular interactions between the N-terminal region and the loop connecting helices IV and V of cytochrome b are proposed.
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Affiliation(s)
- J Y Coppée
- Laboratoire de Génétique Microbienne, Université Catholique de Louvain, Louvain-La-Neuve, Belgium
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16
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Non-native intragenic reversions selected from Saccharomyces cerevisiae cytochrome b-deficient mutants. Structural and functional features of the catalytic center N domain. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41766-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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17
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Meunier B, Colson AM. Insight into the interactions between subunits I and II of the cytochrome c oxidase of the yeast Saccharomyces cerevisiae by means of extragenic complementation. FEBS Lett 1993; 335:338-40. [PMID: 8262179 DOI: 10.1016/0014-5793(93)80414-p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In yeast, revertants were selected from two respiratory deficient mutants carrying mutations in the catalytic subunits of cytochrome oxidase. From a mutant carrying a double mutation in the vicinity of the copper binding pocket in subunit II, two genetically independent revertants were obtained in which the same extragenic reversion mutation was observed, A147V, in the putative helix 4 of subunit I. A comparison with revertants derived from the second deficient mutant, carrying the deficiency mutation, S140L, in the loop 3-4 of subunit I, provides additional data in favour of an interaction between helix 4 of subunit I and subunit II.
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Affiliation(s)
- B Meunier
- Universite Catholique de Louvain, Laboratoire de Genetique Microbienne, Louvain-la-Neuve, Belgium
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18
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Cramer WA, Tae GS, Furbacher PN, Böttger M. The enigmatic cytochrome b-559 of oxygenic photosynthesis. PHYSIOLOGIA PLANTARUM 1993; 88:705-711. [PMID: 28741778 DOI: 10.1111/j.1399-3054.1993.tb01392.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The ubiquitous and obligatory association of cytochrome b-559 with the photosystem II reaction center of oxygenic photosynthesis is a conundrum since it seems not to have a function in the primary electron transport pathway of oxygen evolution. A model for the cytochrome structure that satisfies the cis-positive rule for membrane protein assembly consists of two short, non-identical hydrophobic membrane-spanning polypeptides (α and β), each containing a single histidine residue, as ligands for the bridging heme prosthetic group that is on the side of the membrane opposite to the water splitting apparatus. The ability of the heterodimer, but not the single α-subunit, to satisfy the cis-positive rule implies that the cytochrome inserts into the membrane as a heterodimer, with some evidence implicating it as the first membrane inserted unit of the assembling reaction center. The very positive redox potential of the cytochrome can be explained by a position for the heme in a hydrophobic niche near the stromal aqueous interface where it is also influenced by the large positive dipole potential of the parallel α-helices of the cytochrome. The requirement for the cytochrome in oxygenic photosynthesis may be a consequence of the presence of the strongly oxidizing reaction center needed for H2 O-splitting. This may lead to the need, under conditions of stress or plastid development, for an alternate source of electrons when the H2 O-splitting system is not operative as a source of reductant for the reaction center.
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Affiliation(s)
- William A Cramer
- Dept of Biological Sciences, Purdue Univ., West Lafayette, IN 47907 USA
| | - Gun-Sik Tae
- Dept of Biological Sciences, Purdue Univ., West Lafayette, IN 47907 USA
| | - Paul N Furbacher
- Dept of Biological Sciences, Purdue Univ., West Lafayette, IN 47907 USA
| | - Michel Böttger
- Dept of Biological Sciences, Purdue Univ., West Lafayette, IN 47907 USA
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19
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Abstract
Chemical transformations, like osmotic translocations, are transport processes when looked at in detail. In chemiosmotic systems, the pathways of specific ligand conduction are spatially orientated through osmoenzymes and porters in which the actions of chemical group, electron and solute transfer occur as vectorial (or higher tensorial order) diffusion processes down gradients of total potential energy that represent real spatially-directed fields of force. Thus, it has been possible to describe classical bag-of-enzymes biochemistry as well as membrane biochemistry in terms of transport. But it would not have been possible to explain biological transport in terms of classical transformational biochemistry or chemistry. The recognition of this conceptual asymmetry in favour of transport has seemed to be upsetting to some biochemists and chemists; and they have resisted the shift towards thinking primarily in terms of the vectorial forces and co-linear displacements of ligands in place of their much less informative scalar products that correspond to the conventional scalar energies. Nevertheless, considerable progress has been made in establishing vectorial metabolism and osmochemistry as acceptable biochemical disciplines embracing transport and metabolism, and bioenergetics has been fundamentally transformed as a result.
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Affiliation(s)
- P Mitchell
- Glynn Research Institute, Bodmin, Cornwall, United Kingdom
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20
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Weber BH. Glynn and the conceptual development of the chemiosmotic theory: a retrospective and prospective view. Biosci Rep 1991; 11:577-617. [PMID: 1823599 DOI: 10.1007/bf01130219] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The origin and evolution of the chemiosmotic theory is described particularly in relation to Peter Mitchell's application of it to model oxidative phosphorylation. Much of the deployment, development and evaluation of the theory occurred at the independent laboratory of the Glynn Research Foundation; the value and future of such an institution is discussed. The role of models mediating between theories and phenomena is analyzed with regard to the growth of knowledge of chemiosmotic systems.
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Affiliation(s)
- B H Weber
- Department of Chemistry and Biochemistry, California State University, Fullerton
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Skulachev VP. Chemiosmotic systems in bioenergetics: H(+)-cycles and Na(+)-cycles. Biosci Rep 1991; 11:387-441; discussion 441-4. [PMID: 1668527 DOI: 10.1007/bf01130214] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The development of membrane bioenergetic studies during the last 25 years has clearly demonstrated the validity of the Mitchellian chemiosmotic H+ cycle concept. The circulation of H+ ions was shown to couple respiration-dependent or light-dependent energy-releasing reactions to ATP formation and performance of other types of membrane-linked work in mitochondria, chloroplasts, some bacteria, tonoplasts, secretory granules and plant and fungal outer cell membranes. A concrete version of the direct chemiosmotic mechanism, in which H+ potential formation is a simple consequence of the chemistry of the energy-releasing reaction, is already proved for the photosynthetic reaction centre complexes. Recent progress in the studies on chemiosmotic systems has made it possible to extend the coupling-ion principle to an ion other than H+. It was found that, in certain bacteria, as well as in the outer membrane of the animal cell, Na+ effectively substitutes for H+ as the coupling ion (the chemiosmotic Na+ cycle). A precedent is set when the Na+ cycle appears to be the only mechanism of energy production in the bacterial cell. In the more typical case, however, the H+ and Na+ cycles coexist in one and the same membrane (bacteria) or in two different membranes of one and the same cell (animals). The sets of delta mu H+ and delta mu Na+ generators as well as delta mu H+ and delta mu Na+ consumers found in different types of biomembranes, are listed and discussed.
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Affiliation(s)
- V P Skulachev
- Department of Bioenergetics, A. N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Moscow State University, USSR
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Pasternak CA. Closing symposium remarks. Biosci Rep 1991. [DOI: 10.1007/bf01130218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Affiliation(s)
- Charles A. Pasternak
- Department of Cellular & Molecular Sciences, St George's Hospital Medical School (University of London), London SW17 ORE
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