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Manoj KM, Gideon DA, Jaeken L. Why do cells need oxygen? Insights from mitochondrial composition and function. Cell Biol Int 2021; 46:344-358. [PMID: 34918410 DOI: 10.1002/cbin.11746] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/07/2021] [Accepted: 12/14/2021] [Indexed: 02/03/2023]
Abstract
Mitochondrial membrane-embedded redox proteins are classically perceived as deterministic "electron transport chain" (ETC) arrays cum proton pumps; and oxygen is seen as an "immobile terminal electron acceptor." This is untenable because: (1) there are little free protons to be pumped out of the matrix; (2) proton pumping would be highly endergonic; (3) ETC-chemiosmosis-rotary ATP synthesis proposal is "irreducibly complex"/"non-evolvable" and does not fit with mitochondrial architecture or structural/distribution data of the concerned proteins/components; (4) a plethora of experimental observations do not conform to the postulates/requisites; for example, there is little evidence for viable proton-pumps/pH-gradient in mitochondria, trans-membrane potential (TMP) is non-fluctuating/non-trappable, oxygen is seen to give copious "diffusible reactive (oxygen) species" (DRS/DROS) in milieu, etc. Quite contrarily, the newly proposed murburn model's tenets agree with known principles of energetics/kinetics, and builds on established structural data and reported observations. In this purview, oxygen is needed to make DRS, the principal component of mitochondrial function. Complex V and porins respectively serve as proton-inlet and turgor-based water-exodus portals, thereby achieving organellar homeostasis. Complexes I to IV possess ADP-binding sites and their redox-centers react/interact with O2 /DRS. At/around these complexes, DRS cross-react or activate/oxidize ADP/Pi via fast thermogenic one-electron reaction(s), condensing to form two-electron stabilized products (H2 O2 /H2 O/ATP). The varied architecture and distribution of components in mitochondria validate DRS as (i) the coupling agent of oxidative reactions and phosphorylations, and (ii) the primary reason for manifestation of TMP in steady-state. Explorations along the new precepts stand to provide greater insights on mitochondrial function and pathophysiology.
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Affiliation(s)
- Kelath Murali Manoj
- Department of Biochemistry, Satyamjayatu: The Science & Ethics Foundation, Kerala, India
| | - Daniel Andrew Gideon
- Department of Biochemistry, Satyamjayatu: The Science & Ethics Foundation, Kerala, India
| | - Laurent Jaeken
- Industrial Sciences and Technology, Karel de Grote-Hogeschool, Association University and High Schools Antwerp, Antwerpen, Belgium
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Azzone GF, Luvisetto S. Molecular events in coupling and uncoupling of oxidative phosphorylation. Ann N Y Acad Sci 1988; 550:277-88. [PMID: 2469371 DOI: 10.1111/j.1749-6632.1988.tb35343.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- G F Azzone
- CNR Unit Institute of General Pathology, University of Padova, Italy
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Woelders H, van der Velden T, van Dam K. Unique relationships between the rates of oxidation and phosphorylation and the protonmotive force in rat-liver mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 934:123-34. [PMID: 2837288 DOI: 10.1016/0005-2728(88)90127-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The rate of ATP synthesis (JP) in isolated rat-liver mitochondria was strongly dependent on the magnitude of the protonmotive force (delta mu H+) across the mitochondrial inner membrane. Addition of different concentrations of various uncouplers or malonate to mitochondrial incubations in State 3 led to a depression of delta mu H+ and a concomitant decrease in JP. A unique relationship between JP and delta mu H+ was obtained, which was independent of the way in which delta mu H+ was varied. This unique relationship was observed when K+ (in the presence of valinomycin) was used as a probe for delta psi. Different relationships between JP and delta mu H+ were observed when K+ was used as a probe for delta psi and when K+ was measured after separation of the mitochondria by centrifugation without silicone oil. This led to a serious underestimation of delta psi, specifically when uncouplers were present, and non-unique flow-force relationships were thus obtained. Anomalous relationships between JP and delta mu H+ were also found when TPMP+ was used as a probe for delta psi. However, in uncoupler incubations the presence of TBP- strongly affected the TPMP+ accumulation ratio without any effect on the K+ accumulation or on JP and in the presence of TBP- unique relationships between JP and delta mu H+ were again obtained. This indicates that the accumulation of TPMP+ inside the mitochondria is not a straightforward function of delta psi but also depends on conditions like the presence of TBP- or uncouplers. We conclude that there is a unique relationship between the rate of phosphorylation and the protonmotive force in mitochondria and that under some conditions the behaviour of TPMP+ is anomalous.
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Affiliation(s)
- H Woelders
- Laboratory of Biochemistry, University of Amsterdam, The Netherlands
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Kamp F, Astumian RD, Westerhoff HV. Coupling of vectorial proton flow to a biochemical reaction by local electric interactions. Proc Natl Acad Sci U S A 1988; 85:3792-6. [PMID: 2836858 PMCID: PMC280305 DOI: 10.1073/pnas.85.11.3792] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
For a transmembrane redox enzyme and a (passive) protonophore, the complete set of rate equations is given. Turnover causes cyclic variation of their electric polarization. This is responsible not only for effects of the electric field on the rate constants but also for the generation of an electric field felt by neighboring molecules. It is calculated that, when the systems are close together at a fixed distance, cycling of the two systems becomes coupled enabling the protonophore to pump protons against their electrochemical gradient. If the electrochemical gradient for protons approaches the input force of the redox reaction, slip (incomplete coupling between the chemical and proton-transport reactions) results. By using different sets of parameters, both kinetically reversible and kinetically irreversible proton pumps can be simulated.
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Affiliation(s)
- F Kamp
- National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda, MD 20892
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Rigoulet M, Guerin B, Denis M. Modification of flow-force relationships by external ATP in yeast mitochondria. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 168:275-9. [PMID: 2822409 DOI: 10.1111/j.1432-1033.1987.tb13417.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The purpose of this work is to measure protonmotive force and cytochrome reduction level under different respiratory steady states in isolated yeast mitochondria. The rate of respiration was varied by using three sets of conditions: (a) different external phosphate concentrations with a fixed concentration of ADP (ATP synthesis) and (b) different concentrations of carbonylcyanide m-chlorophenylhydrazone in the presence of oligomycin and carboxyatractylate (uncoupling) either in the absence or (c) in the presence of external ATP. ADP plus phosphate stimulates respiration more than uncoupler at the same protonmotive force value. However, the relationships between respiratory rate and protonmotive force were similar when stimulation was induced either by ADP + Pi or by carbonylcyanide m-chlorophenylhydrazone in the presence of ATP. At the same respiratory rate, cytochrome a + a3 is more reduced by uncoupler than by ADP + Pi additions. However, the relationships between respiratory rate and reduction level of cytochrome-c oxidase are similar both under ATP synthesis and with uncoupling conditions in the presence of external ATP. Control of respiration exerted by cytochrome-c oxidase, and support the view the condition mentioned above. This control was low when the respiratory rate was varied by the ATP synthesis rate; it increased as a function of the respiratory rate with uncoupler in the absence of ATP. ATP decreased this control under uncoupling conditions. These results suggest a regulatory effect of external ATP on cytochrome-c oxidase, and support the view that the relationships between respiratory rate and protonmotive force, on the one hand, and respiratory rate and the reduction level of cytochrome-c oxidase, on the other, depend respectively on the kinetic regulations of the system.
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Affiliation(s)
- M Rigoulet
- Institut de Biologie Cellulaire et de Neurochimie du Centre National de la Recherche Scientifique, Bordeaux, France
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Petronilli V, Pietrobon D, Zoratti M, Azzone GF. Free energy coupling between H+-generating and H+-consuming pumps. Ratio between output and input forces. EUROPEAN JOURNAL OF BIOCHEMISTRY 1986; 155:423-31. [PMID: 3007129 DOI: 10.1111/j.1432-1033.1986.tb09508.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The delta Gp/delta mu H ratio has been measured in mitochondria close to state 4 in the presence of various uncoupler or K+/valinomycin concentrations in media containing either 1 mM or 50 mM Pi. Care has been taken to control the factors affecting delta Gp and delta mu H which could lead to an artefactual increase of the delta Gp/delta mu H ratio above the highest accepted value for the H+/ATP stoichiometry (n = 4, synthesis + transport). In particular, to avoid overestimation of delta Gp due to inactivation of the ATPases at low delta mu H or to the presence of adenylate kinase, the static head state was approached from the side of net ATP synthesis and delta Gp was measured in a state close to static head but still maintaining a residual rate of aerobic phosphorylation. For each concentration of uncoupler or K+, the Pi concentration and/or the adenylate energy charge (EC) as a function of time have been measured as indicators of net ATP synthesis. Only the values of delta Gp measured during a decrease in Pi concentration and/or an increase in EC have been considered to be meaningful for calculations of delta Gp/delta mu H ratios. Both uncouplers and K+ transport cause a marked depression of delta mu H and a parallel depression of the rate of ATP synthesis. However the low rate of ATP synthesis taking place under conditions of low delta mu H eventually results, especially at high Pi concentrations, in a relatively large delta Gp. The delta Gp/delta mu H ratios obtained at the lower delta mu H values exceed 4 and approach 6. Although slightly higher delta Gp/delta mu H ratios are obtained with valinomycin-treated than with uncoupler-treated mitochondria, the pattern of the rise of the force ratio as delta mu H decreases is similar in both cases. An increase of the delta Gp/delta mu H ratio above 4, the maximal accepted H+/ATP stoichiometry is thermodynamically incompatible with the delocalized protonic coupling model.
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Abstract
Theoretical free-energy coupling systems in which the free energy coupling intermediate (e.g., the proton) occurs only in small numbers of molecules per coupling unit are shown to exhibit a number of peculiar properties: (i) the reactions involving the intermediates do not follow conventional kinetic (or nonequilibrium thermodynamic) rate laws in terms of the average concentration or chemical potential of the intermediate, (ii) the variation of the output reaction rate with the average intermediate concentration (or apparent chemical potential) is not unequivocal but depends on whether the input reaction or the leak is varied to alter that concentration, and (iii) when the apparent free energy contained in the average concentration of the intermediate is compared with the average free energy recovered in the output reaction, apparent violations of the second law of thermodynamics can occur. These phenomena are reminiscent of experimental observations in proton-linked free-energy transducing systems that suggest a more direct coupling between electron transfer chains and H+-ATPases than only through a bulk proton gradient, delta muH. Consequently, the chemiosmotic coupling theory can account for those observations if it limits the number of free energy coupling protons per chemiosmotic coupling unit to small values.
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Woelders H, van der Zande WJ, Colen AM, Wanders RJ, van Dam K. The phosphate potential maintained by mitochondria in State 4 is proportional to the proton-motive force. FEBS Lett 1985; 179:278-82. [PMID: 2981706 DOI: 10.1016/0014-5793(85)80534-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Evidence is presented for a proportional relationship between the extramitochondrial phosphate potential (delta Gexp) and the proton-motive force (delta mu H+) across the mitochondrial membrane in rat-liver mitochondria oxidising succinate in State 4, when delta mu H+ is varied by addition of uncouplers or malonate. This relationship was found when precautions were taken to minimise interference with the determination of delta Gexp and delta mu H+ by intramitochondrial nucleotides, adenylate kinase activity, the quenching method, and delta mu H+-dependent changes in matrix volume. A non-proportional delta Gexp/delta mu H+ relationship was obtained when these precautions were omitted. Our results do not support mosaic protonic coupling, but are not necessarily in conflict with other localised coupling schemes.
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Wainio WW. An assessment of the chemiosmotic hypothesis of mitochondrial energy transduction. INTERNATIONAL REVIEW OF CYTOLOGY 1985; 96:29-50. [PMID: 2867062 DOI: 10.1016/s0074-7696(08)60593-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
It is argued that a proton concentration difference and/or a membrane potential is not the form into which the free energy of the oxidation-reduction reactions of the mitochondrial respiratory chain is first transduced. It is suggested that the search for a chemical intermediate should be continued in spite of the conclusion by some investigators that the chemical hypothesis is untenable. It is asked whether pH changes when measured in solutions containing mitochondria can be interpreted as evidence for H+ movements, also, whether there is a continuous, renewable and stable electrochemical proton concentration difference (delta mu H+) across the mitochondrial membrane, and whether in fact the delta mu H+ is a necessary intermediate in the synthesis of ATP. The four postulates of Mitchell's chemiosmotic hypothesis of energy transduction are discussed point by point. It is agreed that "The systems are plugged through a topologically closed insulating membrane," which probably is not "a nonaqueous osmotic barrier," and which probably does not have an unusually "low permeability to solutes and to H+ and OH- in particular" when compared with other membranes. There is disagreement with the statement that "Respiratory and photoredox systems are chemiosmotic membrane-located protonmotive chains" in that it is suggested by others that chemiosmosis is chemically nonexistent and that thermodynamically it would lack control. The subsequent statement, "having a characteristic----H+/2 epsilon- stoichiometry," is rendered uncertain by the experimental findings of values greater than 2H+/2 epsilon-/site and probably as large as 4H+/2 epsilon-/site. The proposal that "The synthetase is a chemiosmotic membrane-located reversible motive ATPase" requires the assumption that the ATP synthetase is the same enzyme as the ATPase, but functioning in the reverse direction. It is considered possible that there are two enzymes in the multi-subunit ATPase complex: one the hydrolase, and the other the synthetase. The further proposal, "having characteristic----H+/P stoichiometry" requires that the ratio be 2 according to Mitchell. However, values of 3, as well as larger values, have been reported by others, which introduces a large element of uncertainty. There is no disagreement with the statement that "There are proton-linked (or hydroxyl ion-linked) solute porter systems for osmotic stabilization and metabolite transport." In fact, this may be the principal reason for having proton efflux or "proton-pumping.''(ABSTRACT TRUNCATED AT 400 WORDS)
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Westerhoff HV, Melandri BA, Venturoli G, Azzone GF, Kell DB. A minimal hypothesis for membrane-linked free-energy transduction. The role of independent, small coupling units. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 768:257-92. [PMID: 6095906 DOI: 10.1016/0304-4173(84)90019-3] [Citation(s) in RCA: 179] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Experimental data are reviewed that are not in keeping with the scheme of 'delocalized' protonic coupling in membrane-linked free-energy transduction. It turns out that there are three main types of anomalies: (i) rates of electron transfer and of ATP synthesis do not solely depend on their own driving force and on delta mu H, (ii) the ('static head') ratio of delta Gp to delta mu H varies with delta mu H and (iii) inhibition of either some of the electron-transfer chains or some of the H+-ATPases, does not cause an overcapacity in the other, non-inhibited proton pumps. None of the earlier free-energy coupling schemes, alternative to delocalized protonic coupling, can account for these three anomalies. We propose to add a fifth postulate, namely that of the coupling unit, to the four existing postulates of 'delocalized protonic coupling' and show that, with this postulate, protonic coupling can again account for most experimental observations. We also discuss: (i) how experimental data that might seem to be at odds with the 'coupling unit' hypothesis can be accounted for and (ii) the problem of the spatial arrangement of the electrical field in the different free-energy coupling schemes.
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11
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Ahmed S. Localised chemiosmosis and active transport of lactose in Escherichia coli. FEBS Lett 1984. [DOI: 10.1016/0014-5793(84)80867-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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12
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Krasinskaya IP, Marshansky VN, Dragunova SF, Yaguzhinsky LS. Relationships of respiratory chain and ATP-synthetase in energized mitochondria. FEBS Lett 1984; 167:176-80. [PMID: 6321235 DOI: 10.1016/0014-5793(84)80856-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The present study reveals that the previously described effect of ATP-synthetase inhibition concomitant with inhibition of respiratory chain functioning may be observed at different absolute values of delta psi on the mitochondrial membrane. This fact points out that the membrane potential is not a unique regulator in coupling of ATP-synthetase and respiratory chain activities. We found, using the double-inhibitor titration technique, that ATP-synthetase inhibition induces proportional inhibition of respiratory chain enzymes and vice versa respiratory chain inhibition induces proportional inhibition of ATP-synthetase. This effect is shown to exist only when osmolarity is close to 150-300 (mosM) (in the physiological range). The coupling effectivity (ADP/O) of mitochondria under these conditions is maximal. Under conditions of high osmolarity (400-600 mosM) the respiratory chain and ATP-synthetase behave as if they were coupled by bulk phase delta -mu H+, from the kinetic point of view.
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AZZONE GIOVANNIFELICE, PIETROBON DANIELA, ZORATTI MARIO. Determination of the Proton Electrochemical Gradient across Biological Membranes. CURRENT TOPICS IN BIOENERGETICS 1984. [DOI: 10.1016/b978-0-12-152513-2.50008-8] [Citation(s) in RCA: 103] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Zoratti M, Pietrobon D, Azzone GF. On the relationship between rate of ATP synthesis and H+ electrochemical gradient in rat-liver mitochondria. EUROPEAN JOURNAL OF BIOCHEMISTRY 1982; 126:443-51. [PMID: 6291930 DOI: 10.1111/j.1432-1033.1982.tb06800.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The relationship between rate of ATP synthesis, JATP, and value of the proton electrochemical gradient, delta mu H, has been analyzed in intact mitochondria. Onset of phosphorylation causes a depression of delta mu H of 1.5 kJ/mol. There is a close parallelism between inhibition of JATP and restoration of delta mu H to its state-4 value during titrations with oligomycin or atractyloside. Titrations with ionophores display the following features: (a) delta mu H can be depressed by 3-4 kJ/mol by valinomycin + K+ without affecting the rate of ATP synthesis; (b) uncouplers abolish JATP completely while depressing delta mu H by 3 kJ/mol; (c) complete abolition of ATP synthesis by inhibitors of electron transport is accompanied by a depression of delta mu H of only 1 kJ/mol. The results indicate that: (a) there is a close functional relationship between redox and ATPase H+ pumps, whereby inhibition of electron transfer is accompanied by simultaneous inhibition of the ATPase H+ pumps; and (b) uncoupling of oxidative phosphorylation is not due to depression of delta mu H per se. The consistence of the present data with either a chemiosmotic model where delta mu H is the sole and obligatory intermediate for energy coupling, or models where there is a direct transfer of energy between the two pumps is discussed.
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Di Virgilio F, Azzone GF. Activation of site I redox-driven H+ pump by exogenous quinones in intact mitochondria. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)34692-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Chapter 23 The Role of Electrogenic Proton Translocation in Mitochondrial Oxidative Phosphorylation. ACTA ACUST UNITED AC 1982. [DOI: 10.1016/s0070-2161(08)60713-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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18
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Westerhoff HV, Simonetti AL, Van Dam K. The hypothesis of localized chemiosmosis is unsatisfactory. Biochem J 1981; 200:193-202. [PMID: 6280679 PMCID: PMC1163524 DOI: 10.1042/bj2000193] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The hypothesis of 'localized' chemiosmosis have been put to an experimental test in the system of oxidative phosphorylation by rat liver mitochondria. We find that the variation of the ratio of phosphate potential to delta muH with delta muH does not depend on how delta muH is varied. This is in conflict with hypotheses of localized chemiosmosis. Of all coupling hypotheses, only the parallel-coupling hypothesis can explain the observations, unless variation of the H+/ATP stoichiometry of the ATPase proton pump is accepted. In the latter case. 'macroscopic' chemiosmosis can explain the observations equally well as hypotheses of localized chemiosmosis. It is concluded that either variation of H+/ATP stoichiometries must be accepted, or that the parallel-coupling hypothesis should be reformulated so that it becomes open to experimental tests.
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Skulachev VP. Integrating functions of biomembranes. Problems of lateral transport of energy, metabolites and electrons. BIOCHIMICA ET BIOPHYSICA ACTA 1980; 604:297-310. [PMID: 6781536 DOI: 10.1016/0005-2736(80)90576-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Lemasters J, Hackenbrock C. The energized state of rat liver mitochondria. ATP equivalence, uncoupler sensitivity, and decay kinetics. J Biol Chem 1980. [DOI: 10.1016/s0021-9258(19)70682-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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23
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24
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Respiration-Linked H+ Translocation in Mitochondria: Stoichiometry and Mechanism. CURRENT TOPICS IN BIOENERGETICS 1980. [DOI: 10.1016/b978-0-12-152510-1.50009-2] [Citation(s) in RCA: 106] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Skulachev VP. Integrating functions of biomebranes problems of lateral transport of energy, metabolites and electrons. ACTA ACUST UNITED AC 1980. [DOI: 10.1016/0304-4157(80)90010-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Azzone G, Pozzan T, Bragadin M, Miconi V. Thermodynamics and kinetics of the H+ pump in mitochondrial electron transport. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(19)86695-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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28
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Brand MD, Harper WG, Nicholls DG, Ingledew WJ. Unequal charge separation by different coupling spans of the mitochondrial electron transport chain. FEBS Lett 1978; 95:125-9. [PMID: 720593 DOI: 10.1016/0014-5793(78)80066-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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31
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Azzone GF, Pozzan T, Massari S. Proton electrochemical gradient and phosphate potential in mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 1978; 501:307-16. [PMID: 620018 DOI: 10.1016/0005-2728(78)90036-1] [Citation(s) in RCA: 86] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The paper reports an analysis of the relationship between deltamuH the proton electrochemical potential difference, and deltaGp, the phosphate potential. Depression of deltamuH and deltaGp has been obtained by titration with: (a) carbonylcyanide trifluoromethoxyphenylhydrazone; (b) nigericin (+ valinomycin); (c) KCl (+ valinomycin); and (d) rotenone. The uncoupler depresses deltamuH more than nigericin (+ valinomycin), KCl (+ valinomycin) and rotenone at equivalent deltaGp. The deltaGp/deltamuH ratio is about 3 at high values of deltamuH. When deltaGp and deltamuH are depressed by nigericin (4 valinomycin) the deltaGp/deltamuH ratio remains constant. When deltaGp and deltamuH are depressed by uncouplers, the deltaGp/deltamuH ratio increases hyperbolically tending to infinity while deltamuH tends to zero. The absence of constant proportionality between deltaGp and deltamuH indicates that the proton gradients driving ATP synthesis presumably operate within microscopic environments.
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