ATP hydrolysis and membrane potential in spinach chloroplasts

Galmiche, J.M.; Girault, G.

doi:10.1016/0014-5793(80)81221-x

Cited by 20 publications

(4 citation statements)

References 13 publications

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“…We suppose that just before the flash is fired the two components of this A/2H, ApH and preflash membrane potential difference are identical in the two experimental conditions. In fact, even if the ApH increases, as a function of the number of flash groups already fired, we have shown (Table I) that it remains the same in the absence and in the presence of ADP and Pi-Slow membrane-potential changes can be recorded by absorbance changes of oxonol VI [21]. We have never seen, before or after ADP and Pi addition, any absorbance change of this dye, reversed by KSCN or valinomycin and potassium ions, in complete darkness or within the 50 s time period 291 following series of flashes.…”

Section: Resultsmentioning

confidence: 82%

Flash-induced ATP synthesis in pea chloroplasts in relation to proton flux

Lemaire¹,

Girault²,

Galmiche³

1985

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Chloroplasts extracted from preilluminated pea seedling leaves have an active ATP synthase. Single turnover flashes induce ATP synthesis in these chloroplasts. This synthesis has been measured by the luminescence of the luciferin-luciferase assay system and the absorbance changes at 515 nm monitored to determine the concomitant proton flux through the ATP-synthase. Variations in the ratio H +/ATP are observed and can be explained by the way ATP synthase is operating. The newly synthesized ATP molecules remain bound to the enzyme, and have variable probabilities to be hydrolysed or released from the enzyme, dependent upon the energized state of the membranes. The lowest value found for the ratio, H +/ATP, is 1.90 + 0.55, which should be very close to the true value.

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Section: Resultsmentioning

confidence: 82%

Flash-induced ATP synthesis in pea chloroplasts in relation to proton flux

Lemaire¹,

Girault²,

Galmiche³

1985

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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“…(i) ATPase activity is stimulated by uncouplers [16]; (ii) ATP hydrolysis is accompanied by the uptake of protons from the medium [17], leading to the formation of a proton concentration gradient (ApH) across the thylakoid membrane [18]; (iii) Using the membrane potential probe oxonol VI,the electrogenic nature of the ATP dependent proton transport was demonstrated [19][20][21]. A~ formation was further supported by the detection of an ATP induced carotenoid electrochromic shift in the dark after light activation [22].…”

Section: Reversal Of Proton Pumping By the Atp Synthasementioning

confidence: 99%

Reverse electron flow in chloroplasts

Shahak

Avron

1986

Photosynth Res

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Energy dependent reverse electron flow reactions in isolated thylakoids provide a unique tool to study, in the dark, the coupling between the ATP synthase, proton transport and the electron transfer system. Appropriate experimental conditions have been established to follow experimentally the following reactions: 1. ATP driven proton uptake into the inner-thylakoid space, which requires preactivation of the ATP synthase. 2. ATP driven reverse electron transport, which involves proton transport as an intermediate, and results in the reduction of QA by an externally added electron donor. 3. ATP driven luminescence, which requires the presence of an oxidized partner on the water side of photosystem II, and involves electron transport from QB to QA. 4. ΔpH driven reverse electron flow, which does not require the participation of the ATP synthase, and uses reduced intermediates between the two photosystems as electron donors for the reduction of QA. 5. ΔpH driven luminescence which again uses reduced intermdiates between the two photosystems as electron donors for QA reduction, and requires the presence of an oxidized partner on the water side of photosystem II. Several of these reactions have been shown to occur in intact chloroplasts and may provide an important regulatory mechanism in vivo.

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“…This transition is thought to be primarily governed by the light-induced membrane potential. Conversely, experiments with intrinsic and extrinsic electric potential probes (Schuurmans etal., 1978(Schuurmans etal., , 1981aGalmiche and Girault, 1980;Girault and Galmiche, 1981;Schreiber and Rienits, 1982) showed a rapid ATP-induced increase of an electric potential, prior to the formation of a transmembrane ApH.…”

Section: Introductionmentioning

confidence: 99%

Energy‐regulated Functional Transitions of Chloroplast Atpase

Schuurmans

Kraayenhof

1983

Photochem & Photobiology

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The functional transitions of the membrane-bound chloroplast ATPase (CF,) as influenced by low ADP and uncoupler concentrations are investigated by measurements of initial and steady-state ATP hyrolysis and concomitant membrane energization. Following activation of latent ATP hydrolysis by light in the presence of dithioerythritol, the resulting steady-state ATP hydrolysis depends on the dark-period ( t d ) bteween light activation and ATP addition. ADP, added during fd, inhibits this activity ( K , about 2 p M ) and induces a lag in the onset of ATP hydrolysis. The extent of membrane energization as monitored by an aminoacridine fluorescent probe is proportional to the ATPase activity.An uncoupler amplifies the inhibitory effect of ADP if added during td, whereas it induces the normal stimulation of ATP hydrolysis in the absence of ADP. The ADP effect, which is different from product inhibition, is interpreted as a conformational interaction with CF,, causing an increase of the energy threshold required for the inactive -+ active transition of the CF, molecules. These results are in harmony with currently proposed models of CF, regulation by adenine nucleotides based on binding studies.The inactive + active transition of CF, conformation is investigated by analysis of the lag in the onset of ATP hydrolysis at different ADP concentrations and by means of varied light pulses and single-turnover flashes, using the electric potential indicating absorption change at 515 nm as a probe for the onset of ATP hydrolysis. The half-time of the process leading to fully (re)activated ATP hydrolysis is about 0.25 s. The ATP-dependent flash-induced inactive + active transition occurs within a few turnovers of electron flow.

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ATP hydrolysis and membrane potential in spinach chloroplasts

Cited by 20 publications

References 13 publications

Flash-induced ATP synthesis in pea chloroplasts in relation to proton flux

Flash-induced ATP synthesis in pea chloroplasts in relation to proton flux

Reverse electron flow in chloroplasts

Energy‐regulated Functional Transitions of Chloroplast Atpase

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