Electron transport and photophosphorylation by Photosystem I in vivo in plants and cyanobacteria

1993 ◽  
Vol 36 (3) ◽  
pp. 149-168 ◽  
Author(s):  
David C. Fork ◽  
Stephen K. Herbert
Keyword(s):  
Electron Transport ◽  
Photosystem I

Ferredoxin–NADP+ reductase is the site of oxygen reduction in pseudocyclic electron transport

1994 ◽  
Vol 72 (2) ◽  
pp. 256-260 ◽  
Author(s):  
D. Christoper Goetze ◽  
Robert Carpentier
Keyword(s):  
Electron Transport ◽  
Oxygen Reduction ◽  
Photosystem I ◽  
Spinacia Oleracea ◽  
Thylakoid Membranes ◽  
Photoelectrochemical Cell ◽  
Reaction Products ◽  
Additional Increase ◽  
Ps I

The effects of ferredoxin (Fd) and Fd–NADP+ reductase (FNR) on the oxygen photoreduction by photosystem I (PS I) in spinach (Spinacia oleracea L.) thylakoid membranes were investigated using a unique photoelectrochemical cell. This cell was previously shown to monitor the Mehler reaction products of photosynthetic oxygen reduction and represents an excellent tool for studying pseudocyclic electron transport. The magnitude of the photocurrent produced by the thylakoids was increased by as much as 40% in the presence of 60 μM Fd. If thylakoids were supplemented by both Fd and FNR, an additional increase of photocurrent was observed. All these reactions were inhibited by catalase, an enzyme that degrades H2O2, to demonstrate that O2 reduction was involved in all the photoreactions studied. The fact that more O2 was consumed in the presence of FNR was interpreted as evidence that the most effective site of oxygen reduction on the acceptor side of PS I is on FNR and not on Fd. The in vivo implication is that during pseudocyclic electron transport, NADP+ and oxygen directly compete for PS I electrons, with the former having significantly faster reaction kinetics. The advantageous physiological consequences of such a competition are (i) pseudocyclic electron transport would represent a true attenuating mechanism of the redox state of the NADP+–NADPH pool, (ii) oxygen would be a contingent acceptor under high illumination stress, helping to cope with the resultant elevated electron transport rates, and (iii) this mechanism is indisputably a faster response to stress than cyclic electron transport. Key words: Spinacia oleracea, photosystem I, thylakoid membranes, ferredoxin–NADP+ reductase, pseudocyclic electron transport, photoelectrochemistry.

Inhibition of Photosynthetic Electron Transport by Halogenated 4-Hydroxy-pyridines

1985 ◽  
Vol 40 (5-6) ◽  
pp. 391-399 ◽  
Author(s):  
A. Trebst ◽  
B. Depka ◽  
S. M. Ridley ◽  
A. F. Hawkins
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Electron Flow ◽  
Essential Element ◽  
Photosynthetic Electron Transport ◽  
Cyclic Electron Flow ◽  
Acceptor Side

Abstract Herbicidal halogen substituted 4-hydroxypyridines are inhibitors of photosynthetic electron flow in isolated thylakoid membranes by interfering with the acceptor side of photosystem II. Tetrabromo-4-hydroxypyridine, the most active compound found, has a pI50-value of 7.6 in the inhibition of oxygen evolution in both the reduction of an acceptor of photosystem I and an acceptor of photosystem II. The new inhibitors displace both metribuzin and ioxynil from the membrane. The 4-hydroxypyridines, like ioxynil, have unimpaired inhibitor potency in Tristreated chloroplasts, whereas the DCMU-type family of herbicides does not. It is suggested that 4-hydroxypyridines are complementary to phenol-type inhibitors, and a common essential element is proposed. The 4-hydroxypyridines do not inhibit photosystem I or non-cyclic electron flow through the cytochrome b/f complex. But they do have a second inhibition site in photosynthetic electron transport since they inhibit ferredoxin-catalyzed cyclic electron flow, indicating an antimycin-like property. A comparison of the in vitro potency of the compounds with the in vivo potency shows no correlation. A major herbicidal mode of action of the group is related to the inhibition of carotenoid synthesis, and access to the chloroplast lamellae in vivo for inhibition of electron transport may be restricted.

scholarly journals In-vivo quantification of electron flow through photosystem I – Cyclic electron transport makes up about 35% in a cyanobacterium

2021 ◽  
Vol 1862 (3) ◽  
pp. 148353
Author(s):  
Marius L. Theune ◽  
Sarah Hildebrandt ◽  
Anja Steffen-Heins ◽  
Wolfgang Bilger ◽  
Kirstin Gutekunst ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem I ◽  
Electron Flow ◽  
Cyclic Electron Transport ◽  
Flow Through

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

1980 ◽  
Vol 35 (9-10) ◽  
pp. 770-775 ◽  
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.

scholarly journals Anticancer gold(iii)-bisphosphine complex alters the mitochondrial electron transport chain to induce in vivo tumor inhibition

2021 ◽  
Author(s):  
Jong Hyun Kim ◽  
Samuel Ofori ◽  
Sean Parkin ◽  
Hemendra Vekaria ◽  
Patrick G. Sullivan ◽  
...  
Keyword(s):  
Electron Transport ◽  
Metal Complexes ◽  
Electron Transport Chain ◽  
Chemical Diversity ◽  
Mitochondrial Electron Transport Chain ◽  
Generate Functional ◽  
Tumor Inhibition ◽  
Transport Chain

Expanding the chemical diversity of metal complexes provides a robust platform to generate functional bioactive reagents.

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.

scholarly journals Flavodiiron proteins act as safety valve for electrons in Physcomitrella patens

2016 ◽  
Vol 113 (43) ◽  
pp. 12322-12327 ◽  
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.

scholarly journals PsaE Is Required for in Vivo Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechococcus sp. PCC 7002

1993 ◽  
Vol 103 (1) ◽  
pp. 171-180 ◽  
Author(s):  
L. Yu ◽  
J. Zhao ◽  
U. Muhlenhoff ◽  
D. A. Bryant ◽  
J. H. Golbeck
Keyword(s):  
Photosystem I ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Synechococcus Sp
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