Copper Ion Inhibition of Electron Transport Activity in Sodium Chloride Washed Photosystem II Particle Is Partially Prevented by Calcium Ion

1996 ◽  
Vol 51 (3-4) ◽  
pp. 179-184 ◽  
Author(s):  
Surendra Chandra Sabat
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Calcium Ion ◽  
Electron Flow ◽  
Copper Ion ◽  
Dependent Manner ◽  
Transport Activity ◽  
Concentration Dependent Manner ◽  
Control Activity ◽  
Electron Transport Activity

Abstract The inhibitory effects of copper ion (Cu2+) on the photosynthetic electron transport func­tion was investigated both in NaCl washed (depleted in 17 and 23 kDa polypeptides) and native (unwashed) photosystem II membrane preparations from spinach (Beta vulgaris) chlo-roplasts. Copper in the range of 2.0 to 15 μᴍ strongly inhibited the electron flow from water to 2,6-dichlorobenzoquinone in NaCl washed particles in a concentration dependent manner. Com plete inhibition was noticed at 15 μᴍ Cu2+. Oppositely in native membranes, 15 μᴍ C u2+ inhibited only 10-12% of control activity. It was found that calcium ion (Ca2+) significantly reduced the Cu2+ inhibition of electron transport activity. The Ca2+ supported prevention of Cu2+ toxicity was specific to Ca2+. Further analysis indicated that both Cu2+ and Ca2+ act competitively. Since Ca2+ is known to have stimulating/stabilizing effect at the donor side of photosystem II, it is therefore suggested that Cu2+ in NaCl washed particles exerts its inhibi­tory effect(s) at the oxidizing side of photosystem stimulates/stabilizes the oxygen evolution.

Effect of Magnesium and Calcium Ions on the Photoelectron Transport Activity of Low-Salt Suspended Hydrilla verticillata Thylakoids: Possible Sites of Cation Interaction

1998 ◽  
Vol 53 (9-10) ◽  
pp. 849-856
Author(s):  
Sujata R. Mishra ◽  
Surendra Chandra Sabat
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Donor ◽  
Water Oxidation ◽  
Electron Flow ◽  
Hydrilla Verticillata ◽  
Transport Activity ◽  
Low Salt ◽  
Electron Transport Activity ◽  
Stimulation Of

Stimulatory effect of divalent cations like calcium (Ca2+) and magnesium (Mg2+) was investigated on electron transport activity of divalent cation deficient low-salt suspended (LS) thylakoid preparation from a submerged aquatic angiosperm, Hydrilla verticillata. Both the cations stimulated electron transport activity of LS-suspended thylakoids having an intact water oxidation complex. But in hydroxylamine (NH2OH) - or alkaline Tris - washed thylakoid preparations (with the water oxidation enzyme impaired), only Ca2+ dependent stimulation of electron transport activity was found. The apparent Km of Ca2+ dependent stimulation of electron flow from H2O (endogenous) or from artificial electron donor (exogenous) to dichlorophenol indophenol (acceptor) was found to be identical. Calcium supported stimulation of electron transport activity in NH2OH - or Tris - washed thylakoids was electron donor selective, i.e., Ca2+ ion was only effective in electron flow with diphenylcarbazide but not with NH2OH as electron donor to photosystem II. A magnesium effect was observed in thylakoids having an intact water oxidation complex and the ion became unacceptable in NH2OH - or Tris - washed thylakoids. Indirect experimental evidences have been presented to suggest that Mg2+ interacts with the water oxidation complex, while the Ca2+ interaction is localized betw een Yz and reaction center of photosystem II.

Inhibitory Effect of Crown Compound on Photoelectron Transport Activity of Beet Spinach Thylakoid Membranes

1991 ◽  
Vol 46 (1-2) ◽  
pp. 87-92 ◽  
Author(s):  
S. C. Sabat ◽  
V. Vijayavergiya ◽  
B. C. Tripathy ◽  
Prasanna Mohanty
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Chlorophyll A ◽  
Chlorophyll A Fluorescence ◽  
Thylakoid Membranes ◽  
Dependent Manner ◽  
Transport Activity ◽  
Concentration Dependent Manner ◽  
Variable Yield ◽  
Spinach Thylakoid

Abstract The effect of K-picrate-18-crown-6 (crown) on the photoelectron transport activity of beet spinach thylakoid membranes was investigated. Addition of micromolar concentration of crown to thylakoid preparation inhibited p-benzoquinone, chloride-indophenol, methyl viologen supported Hill activities maximally by 75 per cent in a concentration dependent manner. However, the photosystem I catalyzed reaction remained insensitive to crown suggesting that crown specifically inhibits photosystem II electron transport. Addition of exogenous electron donors like hydroxylamine or diphenylcarbazide failed to restore the crown induced inhibition of photosystem II electron transport and lowering of steady state chlorophyll a fluorescence yield. These observations suggest that crown also inhibits photosystem II catalyzed electron transport after the donation sites of these exogenous donors. Washing of the crown pre-treated thylakoids with isolation buffer, relieved the crown inhibited electron transport activity, indicating that this inhibition is reversible. Furthermore, in hydroxylamine washed thylakoids which are devoid of O2 evolution capacity, the hydroxylamine induced increase in chlorophyll a fluorescence of variable yield was quenched by the addition of crown. These observations suggest that crown affects the oxygen evolution and inhibits at a site close to photosystem II reaction centres.

Photoinhibition of Electron Transport Activity of Photosystem II in Isolated Thylakoids Studied by Thermoluminescence and Delayed Luminescence

1988 ◽  
Vol 43 (11-12) ◽  
pp. 871-876 ◽  
Author(s):  
Imre Vass ◽  
Narendranath Mohanty ◽  
Sándor Demeter
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Half Life ◽  
Delayed Luminescence ◽  
Transport Activity ◽  
Primary Target ◽  
Electron Transport Activity ◽  
The Stability ◽  
Spinach Thylakoids

Abstract The effect of photoinhibition on the primary (QA) and secondary (QB) quinone acceptors of photosystem I I was investigated in isolated spinach thylakoids by the methods of thermoluminescence and delayed luminescence. The amplitudes of the Q (at about 2 °C) and B (at about 30 °C) thermoluminescence bands which are associated with the recombination of the S2QA- and S2QB charge pairs, respectively, exhibited parallel decay courses during photoinhibitory treatment. Similarly, the amplitudes of the flash-induced delayed luminescence components ascribed to the recombination of S20A and S2OB charge pairs and having half life-times of about 3 s and 30 s, respectively, declined in parallel with the amplitudes of the corresponding Q and B thermoluminescence bands. The course of inhibition of thermoluminescence and delayed luminescence intensity was parallel with that of the rate of oxygen evolution. The peak positions of the B and Q thermoluminescence bands as well as the half life-times of the corresponding delayed luminescence components were not affected by photoinhibition. These results indicate that in isolated thylakoids neither the amount nor the stability of the reduced OB acceptor is preferentially decreased by photoinhibition. We conclude that either the primary target of photodamage is located before the O b binding site in the reaction center of photosystem II or QA and OB undergo simultaneous damage.

Interference of l,2,3,4-Tetramethoxy-5-(2-propenyl)benzene with Photosynthetic Electron Transport

1998 ◽  
Vol 53 (1-2) ◽  
pp. 55-59 ◽  
Author(s):  
A. Jimenez ◽  
R. Mata ◽  
B. Lotina-Hennsen ◽  
A. L. Anaya
Keyword(s):  
Electron Transport ◽  
Electron Flow ◽  
Atp Synthesis ◽  
Photosynthetic Electron Transport ◽  
Stem Bark ◽  
Hill Reaction ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Proton Uptake ◽  
Photosynthetic Activities

AbstractThe effect of 1,2,3,4-tetramethoxy-5-(2-propenyl)benzene, the major phytogrowth-inhibitory agent isolated from the leaves, stem bark and wood of Malmea depressa (Annonaceae), on several photosynthetic activities has been investigated using freshly lysed spinach chloroplasts. The results indicate that this compound inhibits proton-uptake, ATP synthesis and electron flow (basal, phosphorylating and uncoupled) in a concentration dependent manner, therefore acting as a Hill reaction inhibitor. Uncoupled electron transport through photosystem I from reduced dichlorophenol-indophenol to methylviologen is unaffected by this compound. On the other hand, uncoupled electron transport through photosystem II from water to dichlorophenol-indophenol, from water to silicomolibdate and from diphenylcarbazide to dichlorophenol-indophenol is inhibited by this phenylpropanoid, suggesting that the site of inhibition is located in the span from P680 to QA.

Herbicide-Binding Protein, Binding Sites and Electron-Transport Activity: Quantitative Relations

1984 ◽  
Vol 39 (5) ◽  
pp. 430-433 ◽  
Author(s):  
Gerhard Herrmann ◽  
Andreas Thiel ◽  
Peter Böger
Keyword(s):  
Molecular Weight ◽  
Electron Transport ◽  
Photosystem Ii ◽  
Binding Sites ◽  
Binding Protein ◽  
Apparent Molecular Weight ◽  
Transport Activity ◽  
Protein Binding Sites ◽  
Herbicide Binding ◽  
Electron Transport Activity

In Bumilleriopsis filiformis, the thylakoid-membrane protein showing the highest turnover in the light has an apparent molecular weight of 35 kDa. Loss of this protein after chlor-amphenicol treatment leads to a corresponding reduction of herbicide-binding sites as well as photosystem-II activity (measured by e.g. H2O → silicomolybdate) and cellular photosynthesis. This correlation is quantitated by comparison of the amount of herbicide-binding protein (autoradiography), electron transport, and herbicide binding. An increase of the binding constant after chloramphenicol treatment is evident.

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