The coupling factor of photophosphorylation and the electric properties of the thylakoid membrane

Schmid, Roland; Shavit, Noun; Junge, Wolfgang

doi:10.1016/0005-2728(76)90230-9

Cited by 24 publications

(6 citation statements)

References 22 publications

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“…They accumulate protons again if the coupling factor is reincorporated. By flash spectrophotometry it was demonstrated that the electric conductivity of the thylakoid membrane and the proton conductivity are increased by more than two orders of magnitude after extraction of the coupling factor (43,142,144). Thi s suggests that the enzyme is connected to the internal phase by a proton well, which might be formed by its binding protein wi thin the membrane.…”

Section: Energetic Role Of the Electrochemical Potential Differencementioning

confidence: 99%

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Membrane Potentials in Photosynthesis

Junge¹

1977

Annu. Rev. Plant. Physiol.

189

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ISymbols and units used in this paper conform with the recommendations of the IUPAC council (SI units). The system used for electromagnetic quantities is the meter-kilogram second one, with the permittivity of the vacuum (Eo = 8.854 X 10-12 A V-1m-I) introduced to match the units of volt and ampere to the mechanical quantities. Deviating from this notation the length unit A (=IQ-lOm) is used for atomic dimensions.

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Section: Energetic Role Of the Electrochemical Potential Differencementioning

confidence: 99%

“…The acceleration is sensitive to the speci fic antibody against the coupling factor of photophosphorylation[Schmid, Shavit & Jung e(144)]. If an additional electric conductivity is induced, say for potassium ions (by valinomycin) which is as effective as the channel linked to the coupling factor, the ATP yield is halved [Junge, Rumberg & Schroder(73)].…”

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confidence: 99%

Membrane Potentials in Photosynthesis

Junge¹

1977

Annu. Rev. Plant. Physiol.

189

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“…In previous studies we found high electric conductivity of, and proton leakage through, the thylakoid membrane after extraction of CF1 (23,24). These studies were carried out by flash spectrophotometry via the electrochromic absorption changes of certain chloroplast pigments (25) (reviewed in refs.…”

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confidence: 99%

Cooperative transient trapping of photosystem II protons by the integral membrane portion (CF0) of chloroplast ATP-synthase after mild extraction of the four-subunit catalytic part (CF1)

Junge

Hong

et al. 1984

Proc. Natl. Acad. Sci. U.S.A.

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The ATP-synthase in chloroplasts is built from two blocks, CF0, which is integral to the thylakoid membrane and which serves as a proton channel, and CF1, attached to CFO, which is catalytically active. This study is aimed at understanding proton conduction through CF0. By a mild procedure we extracted <10% of total CF1, predominantly the four-subunit CF1 without the 6 subunit. Extracted chloroplasts were excited with short flashes of light and the time course of the transmembrane potential and of the pH changes in both phases was measured spectrophotometrically. Mild extraction of CF1 caused two effects. ('l Up to 50% of the protons rapidly released from water oxidation transiently escaped detection in the thylakoid interior. (it) The initial extent of the transmembrane potential was decreased by some 10% (20-,us resolution). Protons that were not detected inside appeared in the external phase after having passed the thylakoid membrane. pH titrations of the transient loss of protons produced an extremely sharp transition (near pH 7.5) as if six protons were buffered in a strictly cooperative manner. These effects were reversed upon addition of NN'-dicyclohexylcarbodiimide, which, among other actions, blocks the proton channel through CF0. We interpret these observations as follows. (i) CFO incorporates proton binding groups, which can act in a hexacooperative way. These groups are located near the middle of the membrane. (id) After extraction of CF1, protons produced during water oxidation have very rapid access to these groups, but they pass the full span of the membrane more slowly: buffering precedes conduction through CFO.

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“…5B). It is suggested that the release of the CF, from thylakoids opens channels for protons in the membranes (McCarty andRacker 1966, Schmid andJunge 1974) and, thereby, leads to uncoupling (Avron 1963, Hesse et al 1976, Telfer et al 1980; these channels can be blocked by DCCD lowering the proton efflux (Schmid and Junge 1974). Thus, the results clearly point to alterations in the region of the CF,.…”

Section: Resultsmentioning

confidence: 90%

The role of the chloroplast coupling factor in the inactivation of thylakoid membranes at low temperatures

Santarius

1984

Physiologia Plantarum

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Thylakoids isolated from spinach leaves (Spinacia oleracea L. cv. Monatol) were exposed to variable low temperatures under non‐freezing conditions. After incubation, changes in the activities of several photochemical reactions and physical properties of the membranes were measured at room temperature. Cyclic photophosphorylation was strictly dependent on the temperature and the electrolyte concentration: decrease in temperature and increase in NaCl concentration enhanced membrane damage. Inactivation of photophosphorylation was accompanied by stimulation of non‐cyclic electron transport, increase in proton permeability and decrease in δpH. When dicyclohexylcarbodiimide was added, the proton gradient became completely restored. The temperature‐ and salt‐dependent breakdown of photophosporylation was closely related to the release of the chloroplast coupling factor (CF1) from the membranes. The addition of Mg2+, very low concentrations of ATP or ADP, or higher concentrations of low‐molecular‐weight polyols prior to temperature treatment prevented thylakoid damage. The data indicate that inactivation of photophosphorylation of thylakoids at low temperatures is determined to a considerable extent by the cold lability of the CF1. As a consequence, it must be concluded that damage of biomembranes caused by freezing is not due solely to changes resulting from the ice formation but additionally by temperature‐dependent alterations of cold‐labile proteins. Moreover, the data explain the mechanism of non‐colligative cryoprotection of isolated thylakoid membranes.

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The coupling factor of photophosphorylation and the electric properties of the thylakoid membrane

Cited by 24 publications

References 22 publications

Membrane Potentials in Photosynthesis

Membrane Potentials in Photosynthesis

Cooperative transient trapping of photosystem II protons by the integral membrane portion (CF0) of chloroplast ATP-synthase after mild extraction of the four-subunit catalytic part (CF1)

The role of the chloroplast coupling factor in the inactivation of thylakoid membranes at low temperatures

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