The effects of quinone analogues on cytochrome <i>b</i><sub>6</sub> reduction and oxidation in a reconstituted system

Lam, Eric

doi:10.1016/0014-5793(84)81136-9

Cited by 20 publications

(9 citation statements)

References 20 publications

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“…Moreover, this inhibitory effect is completely reversed by the addition of 5 M HQNO (Table I). At this concentration HQNO is known to block electron transfer from cytochrome b to plastoquinone, preventing the oxidation of the cytochrome complex (22,(42)(43)(44). These results, therefore, provide evidence supporting the involvement of reduced cytochrome bf complex in the activation of the thylakoid protein phosphorylation by transient low pH treatment.…”

Section: Cytochrome Bf Complex Is Involved In the Low Ph Activationmentioning

confidence: 52%

Activation/Deactivation Cycle of Redox-controlled Thylakoid Protein Phosphorylation

Vener

Kan

Gal

et al. 1995

Journal of Biological Chemistry

108

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Signal transduction via light-dependent redox control of reversible thylakoid protein phosphorylation has evolved in plants as a unique mechanism for controlling events related to light energy utilization. Here we report for the first time that protein phosphorylation can be activated without light or the addition of reducing agents by a transient exposure of isolated thylakoid membranes to low pH in darkness. The activation of the kinase after incubation of dark-adapted thylakoids at pH 4.3 coincides with an increase in the plastoquinol: plastoquinone ratio up to 0.25. However, rapid plastoquinol reoxidation (<1 min) at pH 7.4 contrasts with the slow kinase deactivation (t1 ⁄2 ‫؍‬ 4 min), which indicates that the redox control is not directly dependent on the plastoquinone pool. Use of inhibitors and a cytochrome bf-deficient mutant of Lemna demonstrate the involvement of the cytochrome bf complex in the low-pH induced protein phosphorylation. EPR spectroscopy shows that subsequent to the transient low pH treatment and transfer of the thylakoids to pH 7.4, cytochrome f, the Rieske Fe-S center, and plastocyanin become reduced and are not reoxidized while the kinase is slowly deactivated. However, the deactivation correlates with a decrease of the EPR g z signal of the reduced Rieske Fe-S center, which is also affected by quinone analogues that inhibit the kinase. Our data point to an activation mechanism of thylakoid protein phosphorylation that involves the binding of plastoquinol to the cytochrome bf complex in the vicinity of the reduced Rieske Fe-S center.Protein phosphorylation plays a major role in cellular signaling, developmental processes, and metabolism regulation of living cells (1-3). In chloroplasts a unique light mediated redox-controlled phosphorylation (4 -7) of a number of proteins associated with the thylakoid membrane has evolved. Phosphorylation of the major light-harvesting chlorophyll a/b protein complex (LHCII) 1 regulates the balance of excitation energy between the two photosystems (5, 6, 8), protects oxygen-evolving organisms against photoinhibition by excessive light excitation (9) and may affect the process of LHCII degradation related to the long term acclimation of the light-harvesting antenna size to the prevailing ambient light intensity (10). Other identified phosphoproteins belong to photosystem II and include the D1 and D2 reaction center protein subunits as well as the chlorophyll a binding protein CP43 and the 9-kDa psbH protein (11,12). Phosphorylation of the D1 polypeptide in higher plants is implicated in the regulation of its degradation during the light induced turnover and repair of photoinhibitory damage to the photosystem II reaction center (13-16).The specific mechanism involved in the redox-mediated activation of the thylakoid kinase(s) is not yet understood. Activation of thylakoid protein phosphorylation is dependent on the redox state of the plastoquinone pool (5-7). In cytochrome bf-deficient mutants of algae (17) and higher plants (18 -20) the redox-controlle...

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Section: Cytochrome Bf Complex Is Involved In the Low Ph Activationmentioning

confidence: 52%

Activation/Deactivation Cycle of Redox-controlled Thylakoid Protein Phosphorylation

Vener

Kan

Gal

et al. 1995

Journal of Biological Chemistry

108

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“…The Q signal and oxygen evolution were both abolished by the photosystem II inhibitor DCMU (Table 1), indicating that the signal arose as a result of photosynthetic electron transport. DNP‐INT is a non‐redox active inhibitor of the cytochrome bf complex that inhibits turnover of the complex by binding to the quinol reducing site [49–51]. The Q signal was not completely abolished by DNP‐INT, although oxygen uptake was completely inhibited and, in its place, oxygen evolution was observed (Fig.…”

Section: Resultsmentioning

confidence: 99%

Voltammetric detection of superoxide production by photosystem II

Cleland

Grace

1999

FEBS Letters

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Oxygen radicals play both pathological and physiological roles in biological systems. The detection of such radicals is difficult due to their transient nature and the presence of highly efficient antioxidant mechanisms. In plants the physiological role of oxygen is twofold, oxygen is produced by the oxidation of water and consumed as an electron acceptor. The direct involvement of oxygen in photosynthetic events exposes the photosynthetic apparatus to a high probability of damage by oxygen radicals. We report here a direct, simple and rapid method for the measurement of superoxide in vitro based on voltammetric detection. It has potential applications for other in vitro systems investigating superoxide production. We show that in addition to the well established production of superoxide from photosystem I, under reducing conditions superoxide is also produced by photosystem II, probably from the Q A site.z 1999 Federation of European Biochemical Societies.

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“…Ascochlorin may be a general quinone analog, as it also inhibits the ubiquinone sites in the ubiquinol oxidases ( E. coli bo and trypanasome alternative oxidase) [25]. In this respect, it resembles the NQNO-type inhibitors that inhibit the complex II, quinol:fumarate reductase [58], formate dehydrogenase, bo -type ubiquinol oxidase [59], glycerol phosphate dehydrogenase[60], cytochrome b 6 f [61], and both the Q o and Q i sites of the cytochrome bc 1 complex [32]. Further, while funiculosin is generally considered to bind at the Q i site, there have been several reports indicating its interaction with the Q o site [62 –64].…”

Section: Discussionmentioning

confidence: 99%

Ascochlorin is a novel, specific inhibitor of the mitochondrial cytochrome bc1 complex

Berry

Huang

Lee

et al. 2010

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Ascochlorin is an isoprenoid antibiotic that is produced by the phytopathogenic fungus Ascochyta viciae. Similar to ascofuranone, which specifically inhibits trypanosome alternative oxidase by acting at the ubiquinol binding domain, ascochlorin is also structurally related to ubiquinol. When added to the mitochondrial preparations isolated from rat liver, or the yeast Pichia (Hansenula) anomala, ascochlorin inhibited the electron transport via CoQ in a fashion comparable to antimycin A and stigmatellin, indicating that this antibiotic acted on the cytochrome bc1 complex. In contrast to ascochlorin, ascofuranone had much less inhibition on the same activities. On the one hand, like the Qi site inhibitors antimycin A and funiculosin, ascochlorin induced in H. anomala the expression of nuclear-encoded alternative oxidase gene much more strongly than the Qo site inhibitors tested. On the other hand, it suppressed the reduction of cytochrome b and the generation of superoxide anion in the presence of antimycin A3 in a fashion similar to the Qo site inhibitor myxothiazol. These results suggested that ascochlorin might act at both the Qi and the Qo sites of the fungal cytochrome bc1 complex. Indeed, the altered electron paramagnetic resonance (EPR) line shape of the Rieske iron-sulfur protein, and the light-induced time resolved cytochrome b and c reduction kinetics of Rhodobacter capsulatus cytochrome bc1 complex in the presence of ascochlorin demonstrated that this inhibitor can bind to both the Qo and Qi sites of the bacterial enzyme. Additional experiments using purified bovine cytochrome bc1 complex showed that ascochlorin inhibits reduction of cytochrome b by ubiquinone through both Qi and Qo sites. Moreover, crystal structure of chicken cytochrome bc1 complex treated with excess ascochlorin revealed clear electron densities that could be attributed to ascochlorin bound at both the Qi and Qo sites. Overall findings clearly show that ascochlorin is an unusual cytochrome bc1 inhibitor that acts at both of the active sites of this enzyme.

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The effects of quinone analogues on cytochrome b₆ reduction and oxidation in a reconstituted system

Cited by 20 publications

References 20 publications

Activation/Deactivation Cycle of Redox-controlled Thylakoid Protein Phosphorylation

Activation/Deactivation Cycle of Redox-controlled Thylakoid Protein Phosphorylation

Voltammetric detection of superoxide production by photosystem II

Ascochlorin is a novel, specific inhibitor of the mitochondrial cytochrome bc1 complex

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The effects of quinone analogues on cytochrome b6 reduction and oxidation in a reconstituted system

Cited by 20 publications

References 20 publications

Activation/Deactivation Cycle of Redox-controlled Thylakoid Protein Phosphorylation

Activation/Deactivation Cycle of Redox-controlled Thylakoid Protein Phosphorylation

Voltammetric detection of superoxide production by photosystem II

Ascochlorin is a novel, specific inhibitor of the mitochondrial cytochrome bc1 complex

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The effects of quinone analogues on cytochrome b₆ reduction and oxidation in a reconstituted system