Interaction of 2-n-heptyl-4-hydroxyquinoline-N-oxide with photosystem II in chloroplasts and subchloroplast particles

Macpeek, Wendy A.; Cohen, William S.

doi:10.1007/bf00743222

Cited by 10 publications

(1 citation statement)

References 33 publications

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“…The results obtained are compiled in Table 1. It shows that the relative amplitude of the nanosecond decay at low light intensity markedly increased in response to an addition of DCMU and HQNO (inhibiting plastoquinone QB oxidation by plastoquinone Qp; Barton et al 1983;Cohen and Barton 1983) and plastoquinone Qc reduction by cytochrome b (Jones and Whitmarsh 1988), but not due to DBMIB and DNP-INT (both inhibiting plastoquinol Qz oxidation in the cytochrome b/fcomplex (Jones and Whitmarsh 1988;Rich et al 1991). Likewise, CCCP, TYFB or PCP have virtually no effect (actually under these conditions the limited sensitivity does not permit to resolve the possibility of fluorescence quenching).…”

Section: Resultsmentioning

confidence: 99%

Inhibition of photosynthetic oxygen evolution by protonophoric uncouplers

Самуилов

Ренгер²,

Paschenko

et al. 1995

Photosynth Res

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The protonophoric uncouplers carbonyl cyanide m-chlorophenylhydrazone (CCCP), 2,3,4,5,6-pentachlorophenol (PCP) and 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole (TTFB) inhibited the Hill reaction with K3[Fe(CN)6] (but not with SiMo) in chloroplast and cyanobacterial membranes (the I50 values were approx. 1-2, 4-6 and 0.04-0.10 μM, respectively). The inhibition is due to oxidation of the uncouplers on the Photosystem II donor side (ADRY effect) and their subsequent reduction on the acceptor side, ie. to the formation of a cyclic electron transfer chain around Photosystem II involving the uncouplers as redox carriers. The relative amplitude of nanosecond chlorophyll fluorescence in chloroplasts was increased by DCMU or HQNO and did not change upon addition of uncouplers, DBMIB or DNP-INT; the HQNO effect was not removed by the uncouplers. The uncouplers did not inhibit the electron transfer from reduced TMPD or duroquinol to methylviologen which is driven by Photosystem I. These data show that CCCP, PCP and TTFB oxidized on the Photosystem II donor side are reduced by the membrane pool of plastoquinone (Qp) which is also the electron donor for K3 [Fe(CN)6] in the Hill reaction as deduced from the data obtained in the presence of inhibitors. Inhibition of the Hill reaction by the uncouplers was maximum at the pH values corresponding to the pK of these compounds. It is suggested that the tested uncouplers serve as proton donors, and not merely as electron donors on the oxidizing side of Photosystem II.

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Section: Resultsmentioning

confidence: 99%

Inhibition of photosynthetic oxygen evolution by protonophoric uncouplers

Самуилов

Ренгер²,

Paschenko

et al. 1995

Photosynth Res

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Effects of 2-(N-Heptyl)- and 2-(N-Nonyl)-4-Hydroxyquinoline N-Oxide (HQNO, NQNO) on Flash-Induced Proton Translocations in Thylakoids

Hong¹,

Hope

1987

Progress in Photosynthesis Research

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Mammalian mitochondrial mutants selected for resistance to the cytochromeb inhibitors HQNO or myxothiazol

Howell

Bantel

Huang

1983

Somat Cell Mol Genet

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Mouse LA9 cell lines were selected for increased resistance to either HQNO or myxothiazol, inhibitors of electron transport which bind to the mitochondrial cytochrome b protein. Two phenotypically distinguishable HQNO-resistant mutants were recovered while the myxothiazol-resistant isolates had a common phenotype. All three mutant phenotypes were transmitted cytoplasmically in cybrid crosses. Biochemical studies further established that for all three mutant types, resistance at the cellular level was paralleled by an increase in inhibitor resistance of mitochondrial succinate-cytochrome c oxidoreductase, the respiratory complex containing cytochrome b. As with the previously described mitochondrial antimycin-resistant mutant, the initial biochemical and genetic studies indicated that these mutations occur within the mitochondrial cytochrome b gene. This conclusion was strongly supported by the results of mtDNA restriction fragment analyses in which it was found that one HQNO-resistant mutant had undergone a small insertion or duplication in the apocytochrome b gene. Finally, all four mitochondrial cytochrome b mutants have been analyzed in both cell plating studies and succinate-cytochrome c oxidoreductase assays to determine the pattern of cross-resistance to inhibitors of cytochrome b other than the one used for selection.

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Interaction of 2-n-heptyl-4-hydroxyquinoline-N-oxide with photosystem II in chloroplasts and subchloroplast particles

Cited by 10 publications

References 33 publications

Inhibition of photosynthetic oxygen evolution by protonophoric uncouplers

Inhibition of photosynthetic oxygen evolution by protonophoric uncouplers

Effects of 2-(N-Heptyl)- and 2-(N-Nonyl)-4-Hydroxyquinoline N-Oxide (HQNO, NQNO) on Flash-Induced Proton Translocations in Thylakoids

Mammalian mitochondrial mutants selected for resistance to the cytochromeb inhibitors HQNO or myxothiazol

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