The Effect of Some Inhibitors of Photosynthetic Electron Transport on the Kinetics of Redox Changes of the Reaction Centre Chlorophyll of Photosystem I (P700) and of Cytochrome f at Sub-Zero Temperatures

1. Photosynthetic electron transport from water to lipophilic Photosystem II acceptors was stimulated 3-5-fold by high concentrations (greater than or equal to 1 M) of salts containing anions such as citrate, succinate and phosphate that are high in the Hofmeister series. 2. In trypsin-treated chloroplasts, K3Fe(CN)6 reduction insensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea was strongly stimulated by high concentrations of potassium citrate, but there was much less stimulation of 2,6-dichloroindophenol reduction in Tris-treated chloroplasts supplied with 1,5-diphenylcarbazide as artificial donor. The results suggest that the main site of action of citrate was the O2-evolving complex of Photosystem II. 3. Photosystem I partial reactions were also stimulated by intermediate concentrations of citrate (up to 2-fold stimulation by 0.6-0.8 M-citrate), but were inhibited at the highest concentrations. The observed stimulation may have been caused by stabilizaton of plastocyanin that was complexed with the Photosystem I reaction centre, 4. At 1 M, potassium citrate protected O2 evolution against denaturation by heat or by the chaotropic agent NaNO3. 5. It is suggested that anions high in the Hofmeister series stimulated and stabilized electron transport by enhancing water structure around the protein complexes in the thylakoid membrane.

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Superoxide-and Ethane-Formation in Subchloroplast Particles: Catalysis by Pyridinium Derivatives

Zeitschrift für Naturforschung C ◽

10.1515/znc-1980-9-1019 ◽

1980 ◽

Vol 35 (9-10) ◽

pp. 770-775 ◽

Cited By ~ 11

Author(s):

E. F. Elstner ◽

H. P. Fischer ◽

W. Osswald ◽

G. Kwiatkowski

Keyword(s):

Electron Transport ◽

Photosystem I ◽

Photosynthetic Electron Transport ◽

Redox Potentials ◽

Light Reaction ◽

Pyridinium Bromide ◽

Superoxide Formation ◽

Fatty Acid Peroxidation ◽

Chlorophyll Bleaching ◽

Ethane Formation

Abstract Oxygen reduction by chloroplast lamellae is catalyzed by low potential redox dyes with E′0 values between -0 .3 8 V and -0 .6 V. Compounds of E′0 values of -0 .6 7 V and lower are inactive. In subchloroplast particles with an active photosystem I but devoid of photosynthetic electron transport between the two photosystems, the active redox compounds enhance chlorophyll bleaching, superoxide formation and ethane production independent on exogenous substrates or electron donors. The activities of these compounds decrease with decreasing redox potential, with one exception: 1-methyl-4,4′-bipyridini urn bromide with an E′0 value of lower -1 V (and thus no electron acceptor of photosystem I in chloroplast lamellae with intact electron transport) stimulates light dependent superoxide formation and unsaturated fatty acid peroxidation in sub chloroplast particles, maximal rates appearing after almost complete chlorophyll bleaching. Since this activity is not visible with compounds with redox potentials below -0 .6 V lacking the nitrogen atom at the 1-position of the pyridinium substituent, we assume that 1 -methyl-4,4′-bi-pyridinium bromide is “activated” by a yet unknown light reaction.

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Flavodiiron proteins act as safety valve for electrons in Physcomitrella patens

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1606685113 ◽

2016 ◽

Vol 113 (43) ◽

pp. 12322-12327 ◽

Cited By ~ 74

Author(s):

Caterina Gerotto ◽

Alessandro Alboresi ◽

Andrea Meneghesso ◽

Martina Jokel ◽

Marjaana Suorsa ◽

...

Keyword(s):

Electron Transport ◽

Photosystem I ◽

Physcomitrella Patens ◽

Safety Valve ◽

Cell Metabolism ◽

Photosynthetic Apparatus ◽

Photosynthetic Electron Transport ◽

Flowering Plants ◽

Knock Out ◽

Electron Sink

Photosynthetic organisms support cell metabolism by harvesting sunlight to fuel the photosynthetic electron transport. The flow of excitation energy and electrons in the photosynthetic apparatus needs to be continuously modulated to respond to dynamics of environmental conditions, and Flavodiiron (FLV) proteins are seminal components of this regulatory machinery in cyanobacteria. FLVs were lost during evolution by flowering plants, but are still present in nonvascular plants such as Physcomitrella patens. We generated P. patens mutants depleted in FLV proteins, showing their function as an electron sink downstream of photosystem I for the first seconds after a change in light intensity. flv knock-out plants showed impaired growth and photosystem I photoinhibition when exposed to fluctuating light, demonstrating FLV’s biological role as a safety valve from excess electrons on illumination changes. The lack of FLVs was partially compensated for by an increased cyclic electron transport, suggesting that in flowering plants, the FLV’s role was taken by other alternative electron routes.

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Photoinactivation of Photosynthetic Electron Transport under Anaerobic and Aerobic Conditions in Isolated Thylakoids of Spinach

Zeitschrift für Naturforschung C ◽

10.1515/znc-1992-1-212 ◽

1992 ◽

Vol 47 (1-2) ◽

pp. 63-68 ◽

Cited By ~ 3

Author(s):

Rekha Chaturvedi ◽

M. Singh ◽

P. V. Sane

Keyword(s):

Electron Transport ◽

Photosynthetic Electron Transport ◽

Oxygen Evolving Complex ◽

Reaction Centre ◽

Ps Ii ◽

Ps I ◽

S2 State ◽

The Stability ◽

Oxygen Evolving ◽

Spinach Thylakoids

Abstract The effect of exposure to strong white light on photosynthetic electron transport reactions of PS I and PS II were investigated in spinach thylakoids in the absence or presence of oxygen. Irrespective of the conditions used for photoinactivation, the damage to PS II was always much more than to PS I. Photoinactivation was severe under anaerobic conditions compared to that in air for the same duration. This shows that the presence of oxygen is required for prevention of photoinactivation of thylakoids. The susceptibility of water-splitting complex in photoinactivation is indicated by our data from experiments with chloride-deficient chloroplast membranes wherein it was observed that the whole chain electron transport from DPC to MV was much less photoinhibited than that from water. The data from the photoinactivation experiments with the Tris-treated thylakoids indicate another photodam age site at or near reaction centre of PS II. DCMU-protected PS II and oxygen-evolving complex from photoinactivation. DCMU protection can also be interpreted in terms of the stability of the PS II complex when it is in S2 state.

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Localization and Function of Cytochrome f in the Thylakoid Membrane

Zeitschrift für Naturforschung C ◽

10.1515/znc-1977-3-420 ◽

1977 ◽

Vol 32 (3-4) ◽

pp. 271-280 ◽

Cited By ~ 17

Author(s):

Georg H. Schmid ◽

Alfons Radunz ◽

Wilhelm Menke

Keyword(s):

Electron Transport ◽

Outer Surface ◽

Thylakoid Membrane ◽

Time Lag ◽

Photosynthetic Electron Transport ◽

Cytochrome F ◽

Antigenic Determinants ◽

Light Reaction ◽

Transport Reaction ◽

Cyclic Photophosphorylation

Abstract A monospecific antiserum to cytochrome f agglutinates stroma-free swellable chloroplasts from tobacco and Antirrhinum. Consequently, antigenic determinants towards which the antiserum is directed are located in the outer surface of the thylakoid membrane. The antiserum inhibits linear photosynthetic electron transport. Just as described earlier for the antiserum to polypeptide 11000 this inhibition develops in the course of the light reaction. Ultrasonication in the presence of anti serum abolishes the light requirement and the maximal inhibition of the electron transport reaction is immediately observed. Electron transport in chloroplasts from a tobacco mutant which ex hibits only photosystem I-reactions is also inhibited by the antiserum. No time lag in the light for the onset of inhibition is observed with these chloroplasts. As chloroplasts of this mutant have only single unfolded thylakoids it appears that light might preponderantly open up partitions. If the light effect is interpreted in this way, cytochrome f should be located in the partition regions but nevertheless in the outer surface of the thylakoid membrane. However, a rearrangement of molecules in the membrane in the light by which the accessibility of cytochrome f is changed can not be excluded. The inhibition of linear electron transport by the antiserum is approximately 50 per cent and can only be increased to 75% upon the addition of antibodies to plastocyanin. The inhibition by the antiserum to cytochrome f as well as the combined inhibition by the antisera to cytochrome f and plastocyanin can be by-passed by DCPiP. It appears that cytochrome f and plastocyanin cannot be connected in series in the electron transport chain but are both closely associated in the thylakoid membrane. PMS-mediated cyclic photophosphorylation in chloroplasts from wild type tobacco and the tobacco mutant NC95 is only inhibited if the chloroplasts are sonicated in the presence of anti serum. If one disregards, that ultrasonication might cause reaction artifacts, it is thinkable that the cytochrome f, involved in the PMS-mediated cyclic photophosphorylation reaction, might be located inside the membrane.

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Rewiring photosynthesis: a photosystem I-hydrogenase chimera that makes H2in vivo

Energy & Environmental Science ◽

10.1039/c9ee03859k ◽

2020 ◽

Vol 13 (9) ◽

pp. 2903-2914 ◽

Cited By ~ 4

Author(s):

Andrey Kanygin ◽

Yuval Milrad ◽

Chandrasekhar Thummala ◽

Kiera Reifschneider ◽

Patricia Baker ◽

...

Keyword(s):

Electron Transport ◽

Hydrogen Production ◽

Photosystem I ◽

Electron Transport Chain ◽

Electron Flow ◽

Photosynthetic Electron Transport ◽

Photosynthetic Electron Transport Chain ◽

Transport Chain

Photosystem I-hydrogenase chimera intercepts electron flow directly from the photosynthetic electron transport chain and directs it to hydrogen production.

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