Adjustable microchemiosmotic character of the proton gradient generated by Systems I and II for photosynthetic phosphorylation in thylakoids

Sigalat, Claude; Haraux, Francis; Kouchkovsky, Françoise de; Hung, Suong Phung Nhu; Kouchkovsky, Yaroslav de

doi:10.1016/0005-2728(85)90191-4

Cited by 50 publications

(15 citation statements)

References 54 publications

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“…Early experiments carried out on thylakoids (Pick et al, 1974) or bacterial chromatophores (Casadio et al, 1978) have shown that when µ + was diminished to a certain value by adding an uncoupler (FCCP) or by lowering the electron flow, a higher steadystate rate of ATP synthesis was obtained in the partially uncoupled system. The same kind of data was obtained with nigericin in thylakoids (Sigalat et al, 1985). Similar results were published for mitochondria (Mandolino et al, 1983; Zoratti & Petronilli, 1985;Petronilli et al, 1991).…”

supporting

confidence: 82%

“…It is clear that the rate of ATP synthesis is not a unique function of but also depends on the way the proton gradient has been adjusted. We had already reported that a given limited by nigericin addition drives a higher rate of photophosphorylation than the same controlled by light intensity (Sigalat et al, 1985(Sigalat et al, ,1988.…”

Section: Resultsmentioning

confidence: 95%

“…Bound calcium and, in steady state, high ATP synthase activity would maintain the integrity of this microcompartment (Chiang & Dilley, 1987;Renganathan et al, 1991). At variance with this view of a semidirect coupling, we have proposed a model where the proton circulation from primary to secondary proton pumps is limited by lateral resistances, which leads to a small loss of energy Sigalat et al, 1985; see also Hong and Junge (1983)]. This kinetic restriction would be especially pronounced in the case of PS2-driven µ +, because water-splitting enzymes and ATPases are located in distinct membrane areas [for a review, see Melis (1991)].…”

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confidence: 99%

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Flow-force relationships in lettuce thylakoids. 2. Effect of the uncoupler FCCP on local proton resistances at the ATPase level

Sigalat¹,

Kouchkovsky²,

Haraux³

1993

Biochemistry

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The relationship between the steady-state proton gradient (delta pH) and the rate of phosphorylation was investigated in thylakoids under various conditions. Under partial uncoupling by carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), the rate of ATP synthesis was reduced by less than expected from the decrease of delta pH. This was observed in the case of the pyocyanine-mediated cyclic electron flow around photosystem 1, but not with the H2O-->photosystem 2-->cytochrome b6f-->photosystem 1-->methyl viologen system. In state 4, a unique relation was found between delta pH and the "phosphate potential", delta Gp, regardless of whether the energy level was controlled by light input or FCCP. The anomalous effect of FCCP on the rate of ATP synthesis disappeared when the ATPase was partially blocked by the reversible inhibitor venturicidin, but not in the presence of tentoxin, an irreversible inhibitor. These results are consistent with the existence of a small kinetic barrier for protons, limiting their access to the ATPase. This resistance would be collapsed by FCCP.

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confidence: 82%

Section: Resultsmentioning

confidence: 95%

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confidence: 99%

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Flow-force relationships in lettuce thylakoids. 2. Effect of the uncoupler FCCP on local proton resistances at the ATPase level

Sigalat¹,

Kouchkovsky²,

Haraux³

1993

Biochemistry

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“…These confficting results have now been resolved by the findings of Beard and Dilley (3,4), Homer and Moudrianakis (18,19), and Sigalat et al (30) that either mechanism of energy coupling can be observed, depending on experimental conditions. Moreover, the coupling response could be reversibly shifted from one mode to the other (4,8).…”

mentioning

confidence: 94%

Intact Chloroplasts Show Ca²⁺-Gated Switching between Localized and Delocalized Proton Gradient Energy Coupling (ATP Formation)

Chiang¹,

Dilley²

1989

Plant Physiol.

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“…According to the chemiosmotic theory, the immediate driving force in the synthesis of ATP from ADP and Pi in mitochondria and similar systems is an electrochemical potential difference of protons (AfH+) across the coupling membrane. Numerous experimental studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] have indicated that the relationship between the rate of ATP synthesis and AfH+ is either exponential or sigmoidal, a consequence of which, in either case, is that small changes in AAH+ are associated with large changes in rate, and vice versa. Similar relationships have been observed to exist between the rate of respiration and A,H+ in mitochondria [13,[21][22][23][24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

An investigation of the relationships between rate and driving force in simple uncatalysed and enzyme-catalysed reactions with applications of the findings to chemiosmotic reactions

Stoner

1992

Biochemical Journal

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Both the rate and the driving force of a reaction can be expressed in terms of the concentrations of the reactants and products. Consequently, rate and driving force can be expressed as a function of each other. This has been done for a single-reactant, single-product, uncatalysed reaction and its enzyme-catalysed equivalent using the van't Hoff reaction isotherm and Haldane's generalized Michaelis-Menten rate equation, the primary objective being explanation of the exponential and sigmoidal relationships between reaction rate and delta mu H+ commonly observed in studies on chemiosmotic reactions. Acquisition of a purely thermodynamic rate vs. driving-force relationship requires recognition of the intensive and extensive variables and maintenance of the extensive variables constant. This relationship is identical for the two reactions and is hyperbolic or sigmoidal, depending on whether the equilibrium constant is smaller or larger than unity. In the case of the catalysed reaction, acquisition of the purely thermodynamic relationship requires the assumption that the enzyme be equally effective in catalysing the forward and backward reactions. If this condition is not met, the relationship is modified by the enzyme in a manner which can be determined from the ratio of the Michaelis constants of the reactant and product. Under conditions of enzyme saturation in respect to reactant+product, the rate vs. driving-force relationship is determined exclusively by the thermodynamics of the reaction and a single kinetic parameter, the magnitude of which is determined by the relative effectiveness of the enzyme in catalysing the forward and backward reactions. In view of this finding, it is pointed out that, since the catalytic components of chemiosmotic reactions appear to be saturated with respect to the reactant-product pair that is varied in experimental rate vs. delta mu H+ determinations, and that, since many complex enzymic reactions conform to the simple Michaelis-Menten equation with respect to a single reactant-product pair when the concentrations of all other reactants and products are maintained constant, one might expect to be capable of simulating the experimental relationships simply from knowledge of the thermodynamics of the reaction and the relative effectiveness of the catalytic component in catalysing the forward and backward reactions using the simple Michaelis-Menten equation. That this expectation appears to be largely correct is demonstrated with model reactions.(ABSTRACT TRUNCATED AT 400 WORDS)

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Adjustable microchemiosmotic character of the proton gradient generated by Systems I and II for photosynthetic phosphorylation in thylakoids

Cited by 50 publications

References 54 publications

Flow-force relationships in lettuce thylakoids. 2. Effect of the uncoupler FCCP on local proton resistances at the ATPase level

Flow-force relationships in lettuce thylakoids. 2. Effect of the uncoupler FCCP on local proton resistances at the ATPase level

Intact Chloroplasts Show Ca²⁺-Gated Switching between Localized and Delocalized Proton Gradient Energy Coupling (ATP Formation)

An investigation of the relationships between rate and driving force in simple uncatalysed and enzyme-catalysed reactions with applications of the findings to chemiosmotic reactions

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Adjustable microchemiosmotic character of the proton gradient generated by Systems I and II for photosynthetic phosphorylation in thylakoids

Cited by 50 publications

References 54 publications

Flow-force relationships in lettuce thylakoids. 2. Effect of the uncoupler FCCP on local proton resistances at the ATPase level

Flow-force relationships in lettuce thylakoids. 2. Effect of the uncoupler FCCP on local proton resistances at the ATPase level

Intact Chloroplasts Show Ca2+-Gated Switching between Localized and Delocalized Proton Gradient Energy Coupling (ATP Formation)

An investigation of the relationships between rate and driving force in simple uncatalysed and enzyme-catalysed reactions with applications of the findings to chemiosmotic reactions

Contact Info

Product

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Intact Chloroplasts Show Ca²⁺-Gated Switching between Localized and Delocalized Proton Gradient Energy Coupling (ATP Formation)