Uncouplers of Spinach Chloroplast Photosynthetic Phosphorylation.

Krogmann, David W.; Jagendorf, André T.; Avron, Mordhay

doi:10.1104/pp.34.3.272

Cited by 287 publications

(102 citation statements)

References 9 publications

(11 reference statements)

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“…Reduction of either trichlorophenol-indophenol dye (at pH 7.2) or of ferricyanide (at pH 8.0, with no additions) is, indeed, more rapid with the water-treated particles than with those protected by MgCl2 (table VI). Mg-protected particles show a typical coupling phenomenon-a more rapid rate of ferricyanide reduction when ADP, P04, and Mg are present thaln without, and(I an inhibition of the rate by ATP (4,5,8,9 (the maximal rate actually observed here is equivalent to a Qo9Chl of about 5,500). It is also of interest that ferricyanide reduction by water damaged particles is actually inhibited above pH 8.3, compared to the controls.…”

Section: Resultsmentioning

confidence: 95%

Uncoupling Phosphorylation in Spinach Chloroplasts by Absence of Cations

Jagendorf

Smith²

1962

Plant Physiol.

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120

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During attempts to prepare active fragments of spinach chloroplasts, we observed major losses of phosphorylative activity following suspension of the chloroplasts in water. This damage was traced to treatments which probably had the effect of removing cations from the chloroplasts, rather than to a simple physical disruption. Indeed, chloroplast fragments have been used successfully in studies of phosphorylation for a considerable time by now (3,18). Evi. dence for the basis of the observed damage and characteristics of the inactivated chloroplasts will be described below. Materials & Methods

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Section: Resultsmentioning

confidence: 95%

Uncoupling Phosphorylation in Spinach Chloroplasts by Absence of Cations

Jagendorf

Smith²

1962

Plant Physiol.

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120

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“…Toxic effects were demonstrated for isolated chloroplasts exposed to high external NH % + concentrations, from which it has been argued that the NH $ and\or NH % + is incorporated into organic compounds to avoid acute NH % + toxicity (Krogmann et al, 1959). Considering cytosolic H + buffer capacities of c. 50 mM pH −" (Guern et al, 1991), a large cytosolic pH shift need not be expected, and in fact has not been observed in Sinapis root hairs (Herrmann & Felle, 1995).…”

Section: Physiological Consequencesmentioning

confidence: 99%

“…NH $ and NH % + taken up into chloroplasts may be inhibitory to photosynthesis (Krogmann et al, 1959), and light\dark responses of apoplastic pH at least in part reflect proton fluxes across the thylakoid membranes (Mu$ hling et al, 1995). It was therefore of interest to investigate the effect of NH $ treatment on apoplastic pH.…”

Section: Effects Of Nh $ On Apoplastic Ph and [Nh % + ] Of Intact Leavesmentioning

confidence: 99%

The influence of atmospheric NH₃ on the apoplastic pH of green leaves: a non‐invasive approach with pH‐sensitive microelectrodes

Hanstein

Felle

1999

New Phytologist

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The apoplastic pH of intact green leaves of Bromus erectus was measured non-invasively by inserting blunt microelectrodes through stomatal openings. After making electrical contact, the recorded signal was stable for hours, yielding a pH of 4.67p0.10. The leaves responded to ' light-off ' with an initial transient acidification and subsequent sustained alkalinization of 0.2-0.3 pH ; ' light-on ' caused the opposite response. Flushing the leaves with 280 nmol NH $ mol −" air within 18p6 s alkalinized the apoplast by 0.22p0.07 pH, followed by a slower pH increase to reach a steady-state alkalinization of 0.53p0.14 after 19p7 min. This pH shift was persistent as long as the NH $ was flushed, and readily returned to its initial value after replacing the NH $ with clean air. The resultant [NH % + ] increase within the apoplast was measured with a NH % + -selective microelectrode. In the presence of 280 nmol NH $ mol −" air, apoplastic NH % + initially increased within 15p10 s to 1.53p0.41 mM, to reach a steady state of 1.62p0.16 mM after 27p7 min. An apoplastic buffer capacity of 6 mM pH −" unit was calculated from the initial changes of pH and [NH % + ], whereas the steady-state values yielded 2.7 mM pH −" . Infiltrated leaves responded to NH % + with concentration-dependent depolarizations, the maxima of which yielded saturation kinetics indicating carrier-mediated NH % + uptake into adjacent cells, as well as a linear component indicating nonspecific transport. We infer that the initial alkalinization is due to rapid conversion of NH $ to NH % + , whereas the slower pH increase would be caused by regulatory processes involving both membrane transport, and (mainly) NH % + assimilation. Possible consequences of the NH $ -induced pH shift for the development of plants growing in polluted areas are discussed.

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“…Hence, if one substance is found to be only a proton translocator but not an accelerating agent, then the pH gradient can not be the main stabilisor for the trapped holes. It is known that NH4C1 destroys the p H gradient across the thylakoid membrane [29,30].…”

Section: Methodsmentioning

confidence: 99%

Studies on the Mechanism of the Water Oxidation in Photosynthesis

Ренгер¹

1972

Eur J Biochem

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The effect of a number of substances on the rate of the deactivation reactions of the oxidizing equivalents stored in the water-splitting enzyme system Y (these oxidizing equivalents are designated as trapped holes) has been investigated in spinach chloroplasts. The following conclusions were reached.1. A number of substances, the so-called accelerating agents (acceleration of the deactivation reactions of the water-splitting enzyme system Y), accelerate the discharge rate of the trapped holes.2. The accelerating effect is not influenced by the electrical field across the thylakoid membrane. It is only slightly dependent on glutaraldehyde fixation of the chloroplasts and is not caused by accelerating agents inducing irreversible conformational changes in the chloroplasts. Furthermore, for stoichiometrical reasons the accelerating effect is not explainable by the reduction of the trapped holes with accelerating agents as irreversible electron donors.3. The stability of the trapped holes is not influenced by uncouplers of the ammonium iontype, by proton buffers such as imidezole or by ionophores (e.g. nonactin).From these results it is suggested that the accelerating agents only act as catalysts for the natural discharge reactions of the trapped holes.A molecular mechanism for the photosynthetic water oxidation is proposed and the accelerating effect is explained on the basis of this mechanism. The open questions concerning the deactivation reactions of the trapped holes are discussed.The nature of the photosynthetic water-splitting enzyme system Y mediating the oxidation of H,O induced by chlorophyll a11 [1,2] is unknown (see Fig. 1). For the water oxidation to molecular oxygen either by electrolysis or by photolysis the cooperation of four holes (oxidizing equivalents) is required. I n this respect a number of fundamental questions arise. a) Which mechanism generates the holes responsible for the water oxidation in the photosynthetic apparatus ? b) What is the spatial arrangement of these trapped holes ? c) I n which way is the fundamental cooperativity of four holes realized in the oxygen-evolving system Y of photosynthesis?Taking into account the facts so far known about the water-splitting enzyme system Y the following conclusions can be made [7,8] (see Fig. 2).a) The holes produced by photosystem I1 and primarily localized at the primary donor D (these holes are designated as free holes) are not able to oxidize the water molecules directly. b) A secondary donor system, Mn, containing manganese in a definite valence state and probably chloride as functional elements is the site of the oxygen-evolving enzymatic activity.

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Uncouplers of Spinach Chloroplast Photosynthetic Phosphorylation.

Cited by 287 publications

References 9 publications

Uncoupling Phosphorylation in Spinach Chloroplasts by Absence of Cations

Uncoupling Phosphorylation in Spinach Chloroplasts by Absence of Cations

The influence of atmospheric NH₃ on the apoplastic pH of green leaves: a non‐invasive approach with pH‐sensitive microelectrodes

Studies on the Mechanism of the Water Oxidation in Photosynthesis

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Uncouplers of Spinach Chloroplast Photosynthetic Phosphorylation.

Cited by 287 publications

References 9 publications

Uncoupling Phosphorylation in Spinach Chloroplasts by Absence of Cations

Uncoupling Phosphorylation in Spinach Chloroplasts by Absence of Cations

The influence of atmospheric NH3 on the apoplastic pH of green leaves: a non‐invasive approach with pH‐sensitive microelectrodes

Studies on the Mechanism of the Water Oxidation in Photosynthesis

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The influence of atmospheric NH₃ on the apoplastic pH of green leaves: a non‐invasive approach with pH‐sensitive microelectrodes