Modulation of coupling factor ATPase activity in intact chloroplasts

Mills, John D.; Mitchell, Peter; Schürmann, Peter

doi:10.1016/0014-5793(80)80173-6

Cited by 210 publications

(106 citation statements)

References 18 publications

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“…After a dark/light transient, N03-uptake increases without a lag-phase, which is always present in NAR-activation (lag about 10 min; Ref. 13 Probably, TR directly stimulates N03 uptake, similar to the stimulation of a chloroplastic ATPase reported by Mills et al (6), the energy supply of the N03 carrier being regulated by TR. An association between an ATPase and NAR/NO3 carrier has already been suggested (1).…”

Section: Discussionmentioning

confidence: 70%

A Thioredoxin-Mediated Activation of Glutamine Synthetase and Glutamate Synthase in Synchronous Chlorella sorokiniana

Tischner¹,

Schmidt²

1982

Plant Physiol.

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The effects of thioredoxin, dithioerythrol, and mixtures of both on enzymes involved in N metabolism of Chlorella sorokiniana have been studied. Glutamine synthetase, inactivated in vivo, was activated 8-fold by thioredoxin and dithioerythrol. By the same treatment, the activity of glutamate synthase was stimulated nearly 4-fold. Thus, two key enzymes of N metabolism were shown to be regulated via thioredoxin. The enzymes of the nitrate reducing system, i.e. nitrate reductase and nitrite reductase, were not affected by thiols. From these results, a model of NO3-metabolism is put forward which considers the regulating effect of light.The enzymes of the nitrate reducing system (i.e. nitrate reductase, nitrite reductase) were activated by light (I1). Such a lightmediated activation, without a de novo synthesis, was also demonstrated for glutamine synthetase and glutamate synthase (12). A thioredoxin-dependent activation of glutamine synthetase, which was partly purified from Chlorella and then inactivated in vitro, has been previously reported (8). In this paper, we concern ourselves with the role of thioredoxin in the light activation of enzymes related to nitrate assimilation. MATERIALS AND METHODSIn all experiments, synchronous cultures of Chlorella sorokiniana were used (high-temperature strain 211-8k of the algal collection of the Pflanzenphysiologisches Institut, University of Gottingen). Cultivation and synchronization procedures are described by Pirson et al (7). For our experiments, the cells were cultivated in a 7:17 (h/h) light:dark change in order to reach complete inactivation of the enzymes during the prolonged dark period.The preparation of the cell-free supernatant and the enzyme assays have been published previously (14). The values of GSactivity always relate to a synthetase assay.Activation Procedure. Thioredoxin, DTE,2 and TR plus DTE, respectively, were added to the enzyme assays in the given amounts. The reaction vessels were incubated at 30°C for 10 min. Then the enzyme reactions were started by the addition of the substrate. The thioredoxin used was identical to that previously prepared from spinach (TRf) (16). ' Supported by a grant from Deutsche Forschungsgemeinschaft to R. T.and A. S. 2 Abbreviations: DTE, dithioerythrol; TR, thioredoxin; NAR, nitrate reductase; NIR, nitrite reductase; GS, glutamine synthetase; GOGAT, glutamate synthase. RESULTSWith the onset of the illumination, the activity of NAR and NIR is stimulated 28-fold, and that of GS and GOGAT, 10-fold and 4-fold, respectively. These increases in activity are based on an activation of these enzymes already present in the cells and not on their de novo synthesis (11,12). A treatment of partly purified preparations from Chlorella autospores at the end of the synchronous lifecycle with TR, DTE, or TR plus DTE stimulated neither NAR nor NIR (Table I).In contrast, we succeeded in activating GS in those extracts, where the enzymes were present in an inactivated form in vivo. (Fig. 1). Only when presented together do TR and D...

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Section: Discussionmentioning

confidence: 70%

A Thioredoxin-Mediated Activation of Glutamine Synthetase and Glutamate Synthase in Synchronous Chlorella sorokiniana

Tischner¹,

Schmidt²

1982

Plant Physiol.

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“…However, ATP hydrolysis has been observed in intact chloroplasts following illumination in the absence of exogenous thiol [12,13], and it has been suggested that reduced thioredoxin can substitute for dithiothreitol in vivo [14]. The thiol modification which elicits ATP hydrolysis by CF, in vitro may therefore occur under physiological conditions (and may trigger ATP synthetic activity as well [IS] The mechanism by which ATP hydrolytic activity is induced in spinach CF, , both on and off the membrane, is not well understood.…”

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confidence: 99%

Activation of ATPase of spinach coupling factor 1. Release of tightly bound ADP from the soluble enzyme

Sherman

Wimmer

1984

Eur J Biochem

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Several seemingly unrelated procedures used to elicit the latent ATPase activity of soluble spinach coupling factor 1 can be correlated to the release of tightly-bound ADP from the uncoupled enzyme. This ADP release is further enhanced by the presence of medium nucleotides, especially substrate ATP, and may or may not involve release from the catalytic site itself. Similarly, the light/dithiothreitol activation of membrane-bound CF, ATPase is reported to be accompanied by energy-dependent ADP dissociation. Further indication that ADP release is involved in the ATPase activation mechanism is the observation that a pyruvate kinase phosphoenolpyruvate trap for ADP released during light/dithiothreitol treatment greatly retards the decay of membrane-bound ATPase activity that occurs in the dark, presumably by preventing reassociation of ADP. The time course of CF, reactivation by light, after light/dithiothreitol activation followed by dark decay, allows a distinction to be made between the apparently rate-limiting dithiol modification and the more rapid dissociation of tightly bound ADP.Osmotically shocked spinach chloroplasts (outer membrane ruptured and stroma removed) catalyze the synthesis of ATP when energized in the presence of ADP and Pi. These

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“…Activation of a urea cycle enzyme, carbamoyl phosphate synthetase, in rat liver is the only reported case [30]. Thioredoxin activation of ATP synthesis is a distinct possibility, and ought to be tested, in view of the thiol modulation and interaction of thioredoxin with the proton ATPase (CFo-CFI) of chloroplasts [31] and the general similarities of energy-producing mechanisms in chloroplasts and mitochondria.…”

Section: Discussionmentioning

confidence: 99%

Animal and plant mitochondria contain specific thioredoxins

1989

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Thioredoxins have been purified from pig heart and potato tuber mitochondria which differ in chromatographic behaviour, enzyme activating capacity, and slightly higher molecular mass (M,= 12 500) from the major thioredoxin(s) present in mitochondria-free fractions of the same tissue. Both mt-thioredoxins can serve as hydrogen donor for E.&i ribonucleotide reductase but only the plant protein activates spinach chloroplast NADP malate dehydrogenase in vitro. Mitochondrial target enzymes specifically activated by thioredoxin have not as yet been identified.

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Modulation of coupling factor ATPase activity in intact chloroplasts

Cited by 210 publications

References 18 publications

A Thioredoxin-Mediated Activation of Glutamine Synthetase and Glutamate Synthase in Synchronous Chlorella sorokiniana

A Thioredoxin-Mediated Activation of Glutamine Synthetase and Glutamate Synthase in Synchronous Chlorella sorokiniana

Activation of ATPase of spinach coupling factor 1. Release of tightly bound ADP from the soluble enzyme

Animal and plant mitochondria contain specific thioredoxins

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