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פותח על ידי קלירמאש פתרונות בע"מ -
Sulfide-induced sulfide-quinone reductase activity in thylakoids of Oscillatoria limnetica
Year:
1991
Source of publication :
Journal of Biological Chemistry
Authors :
שחק, יוספה
;
.
Volume :
266
Co-Authors:
Arieli, B., Division of Microbial and Molecular Ecology, Institute of Life Sciences, Hebrew University, 91904 Jerusalem, Israel
Padan, E., Division of Microbial and Molecular Ecology, Institute of Life Sciences, Hebrew University, 91904 Jerusalem, Israel
Shahak, Y., Division of Microbial and Molecular Ecology, Institute of Life Sciences, Hebrew University, 91904 Jerusalem, Israel
Facilitators :
From page:
104
To page:
111
(
Total pages:
8
)
Abstract:
Sulfide-dependent partial electron-transport reactions were studied in thylakoids isolated from cells of the cyanobacterium Oscillatoria limnetica, which had been induced to perform sulfide-driven anoxygenic photosynthesis. It was found that these thylakoids have the capacity to catalyze electron transfer, from sulfide to added quinones, in the dark. Assay conditions were developed to measure the reaction either as quinone-dependent sulfide oxidation (colorimetrically) or as sulfide-dependent quinone reduction (by UV dual-wavelength spectrophotometry). The main features of this reaction are as follows. (i) It is exclusively catalyzed by thylakoids of sulfide-induced cells. Noninduced thylakoids lack this reaction. (ii) Plastoquinone-1 or -2 are equally good substrates. Ubiquinone-1 and duroquinone yield somewhat slower rates. (iii) The apparent K(m) for plastoquinone-1 was 32 μM and for sulfide about 4 μM. Maximal rates (at 25 °C) were about 75 μmol of quinone reduced per mg of chlorophyll ·h. (iv). The reaction was not affected by extensive washes of the membranes. (v) Unlike sulfide dependent NADP photoreduction activity of these thylakoids, which is sensitive to all the specific inhibitors of the cytochrome b6f complex, the new dark reaction exhibited differential sensitivity to these inhibitors. 2-n-Nonyl-4-hydroxyquinoline-N-oxide was the most potent inhibitor of both light and dark reactions, working at submicromolar concentrations. 5-n-Undecyl-6-hydroxy-4,7-dioxobenzothiazole also inhibited the two reactions to a similar extent, but at 10 times higher concentrations than 2-n-nonyl-4-hydroxyquinoline-N-oxide. 2,5-Dibromo-3-methyl-6-isopropyl-p-benzoquinone, 2-iodo-6-isopropyl-3-methyl-2',4,4'-trinitrodiphenyl ether, and stigmatellin had no effect on the dark reaction at concentrations sufficient to fully inhibit the light reaction from sulfide. We propose that the sulfide-induced factor which enables the use of sulfide as the electron donor for anoxygenic photosynthesis in Oscillatria limnetica is a membrane-bound sulfide-quinone reductase. Its site of interaction is suggested to be either the cytochrome b6 (at the Q(c) quinone binding site or the b(H) site) or the plastoquinone pool. The analogy to other anoxygenic photosynthetic systems is discussed.
Note:
Related Files :
Cyanobacteria
enzyme induction
Kinetics
light
Models, Biological
Oscillatoria limnetica
photosynthesis
sulfide
thylakoid membrane
עוד תגיות
תוכן קשור
More details
DOI :
Article number:
Affiliations:
Database:
סקופוס
Publication Type:
מאמר
;
.
Language:
אנגלית
Editors' remarks:
ID:
19676
Last updated date:
02/03/2022 17:27
Creation date:
16/04/2018 23:30
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Scientific Publication
Sulfide-induced sulfide-quinone reductase activity in thylakoids of Oscillatoria limnetica
266
Arieli, B., Division of Microbial and Molecular Ecology, Institute of Life Sciences, Hebrew University, 91904 Jerusalem, Israel
Padan, E., Division of Microbial and Molecular Ecology, Institute of Life Sciences, Hebrew University, 91904 Jerusalem, Israel
Shahak, Y., Division of Microbial and Molecular Ecology, Institute of Life Sciences, Hebrew University, 91904 Jerusalem, Israel
Sulfide-induced sulfide-quinone reductase activity in thylakoids of Oscillatoria limnetica
Sulfide-dependent partial electron-transport reactions were studied in thylakoids isolated from cells of the cyanobacterium Oscillatoria limnetica, which had been induced to perform sulfide-driven anoxygenic photosynthesis. It was found that these thylakoids have the capacity to catalyze electron transfer, from sulfide to added quinones, in the dark. Assay conditions were developed to measure the reaction either as quinone-dependent sulfide oxidation (colorimetrically) or as sulfide-dependent quinone reduction (by UV dual-wavelength spectrophotometry). The main features of this reaction are as follows. (i) It is exclusively catalyzed by thylakoids of sulfide-induced cells. Noninduced thylakoids lack this reaction. (ii) Plastoquinone-1 or -2 are equally good substrates. Ubiquinone-1 and duroquinone yield somewhat slower rates. (iii) The apparent K(m) for plastoquinone-1 was 32 μM and for sulfide about 4 μM. Maximal rates (at 25 °C) were about 75 μmol of quinone reduced per mg of chlorophyll ·h. (iv). The reaction was not affected by extensive washes of the membranes. (v) Unlike sulfide dependent NADP photoreduction activity of these thylakoids, which is sensitive to all the specific inhibitors of the cytochrome b6f complex, the new dark reaction exhibited differential sensitivity to these inhibitors. 2-n-Nonyl-4-hydroxyquinoline-N-oxide was the most potent inhibitor of both light and dark reactions, working at submicromolar concentrations. 5-n-Undecyl-6-hydroxy-4,7-dioxobenzothiazole also inhibited the two reactions to a similar extent, but at 10 times higher concentrations than 2-n-nonyl-4-hydroxyquinoline-N-oxide. 2,5-Dibromo-3-methyl-6-isopropyl-p-benzoquinone, 2-iodo-6-isopropyl-3-methyl-2',4,4'-trinitrodiphenyl ether, and stigmatellin had no effect on the dark reaction at concentrations sufficient to fully inhibit the light reaction from sulfide. We propose that the sulfide-induced factor which enables the use of sulfide as the electron donor for anoxygenic photosynthesis in Oscillatria limnetica is a membrane-bound sulfide-quinone reductase. Its site of interaction is suggested to be either the cytochrome b6 (at the Q(c) quinone binding site or the b(H) site) or the plastoquinone pool. The analogy to other anoxygenic photosynthetic systems is discussed.
Scientific Publication
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