Effects of Triazines on Energy Relations of Mitochondria and Chloroplasts

Weed Science ◽  
1974 ◽  
Vol 22 (2) ◽  
pp. 164-166 ◽  
Author(s):  
O. C. Thompson ◽  
B. Truelove ◽  
D. E. Davis
Keyword(s):  
Phaseolus Vulgaris ◽  
Pisum Sativum ◽  
Rat Liver ◽  
Potent Inhibitor ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Cyclic Photophosphorylation ◽  
Energy Relations

The effects of eights-triazines on respiration of (Phaseolus vulgarisL. ‘Black Valentine’) bean and rat liver mitochondria and on cyclic photophosphorylation of pea (Pisum sativumL. ‘Thomas Laxton’) chloroplasts were determined. All triazines inhibited state 3 respiration and cyclic photophosphorylation. The degree of inhibition was similar in both rat liver and bean mitochondria. Prometryne [2,4-bis-(isopropylamino)-6-(methylthio)-s-triazine] was the most potent inhibitor of both respiration and cyclic photophosphorylation. Triazines with the methylthio group showed the most activity, followed by those with the methoxy and chloro substituents in that order.

scholarly journals Acclimation of leaves to low light produces large grana: the origin of the predominant attractive force at work

2012 ◽  
Vol 367 (1608) ◽  
pp. 3494-3502 ◽  
Author(s):  
Husen Jia ◽  
John R. Liggins ◽  
Wah Soon Chow
Keyword(s):  
Thylakoid Membranes ◽  
Enthalpy Change ◽  
Attractive Force ◽  
Gibbs Free Energy Change ◽  
Photosynthetic Membrane ◽  
Low Light ◽  
Cyclic Photophosphorylation ◽  
Thylakoid Stacking ◽  
Endothermic Process ◽  
Fine Tune

Photosynthetic membrane sacs (thylakoids) of plants form granal stacks interconnected by non-stacked thylakoids, thereby being able to fine-tune (i) photosynthesis, (ii) photoprotection and (iii) acclimation to the environment. Growth in low light leads to the formation of large grana, which sometimes contain as many as 160 thylakoids. The net surface charge of thylakoid membranes is negative, even in low-light-grown plants; so an attractive force is required to overcome the electrostatic repulsion. The theoretical van der Waals attraction is, however, at least 20-fold too small to play the role. We determined the enthalpy change, in the spontaneous stacking of previously unstacked thylakoids in the dark on addition of Mg 2+ , to be zero or marginally positive (endothermic). The Gibbs free-energy change for the spontaneous process is necessarily negative, a requirement that can be met only by an increase in entropy for an endothermic process. We conclude that the dominant attractive force in thylakoid stacking is entropy-driven. Several mechanisms for increasing entropy upon stacking of thylakoid membranes in the dark, particularly in low-light plants, are discussed. In the light, which drives the chloroplast far away from equilibrium, granal stacking accelerates non-cyclic photophosphorylation, possibly enhancing the rate at which entropy is produced.

Studies on the Mechanism of NAD-photoreduction by Chromatophores of the Facultative Phototroph, Rhodopseudomonas capsulata

1969 ◽  
Vol 24 (1) ◽  
pp. 67-76 ◽  
Author(s):  
J.-H. Klemme
Keyword(s):  
Nicotinamide Adenine Dinucleotide ◽  
Molecular Hydrogen ◽  
Reaction System ◽  
Electron Donors ◽  
Rhodopseudomonas Capsulata ◽  
Antimycin A ◽  
Inhibitory Effects ◽  
Carbonyl Cyanide ◽  
Cyclic Photophosphorylation ◽  
Energy Dependent

The light-driven and the ATP-driven reduction of nicotinamide adenine dinucleotide (NAD) catalyzed by the chromatophore fraction of Rhodopseudomonas capsulata was investigated. Efficient electron donors for the photoreduction of NAD are molecular hydrogen and succinate. In the ATP-dependent reaction system, succinate is a more efficient electron donor than H2. The energydependent NAD-reduction is driven by ATP, but not by pyrophosphate or ADP. Oligomycin stimulates the NAD-photoreductions and completely inhibits the ATP-driven NAD-reductions. Rotenone and piericidin A are inhibitors for both the light-driven and the ATP-driven NAD-reductions. Antimycin A is an inhibitor only for the light-driven reductions. The H2-linked NAD-photoreduction is less sensitive to these inhibitors and to the uncoupler desaspidin than the succinate-linked reduction. Atebrine, carbonyl cyanide-m-chlorophenylhydrazone, 2,4-dinitrophenol and phenazonium methosulfate are inhibitors for the light-driven and the ATP-driven reductions. Some of the compounds used as inhibitors of the NAD-reduction were also investigated with concerns to their inhibitory effects on cyclic photophosphorylation and O2-linked oxidations of reduced NAD, succinate and H2. Based on the results of these inhibitor studies, the relationships between cyclic photophosphorylation, light-induced noncyclic electron transport and energy-dependent NAD-reduction are discussed.

Localization and Function of Cytochrome f in the Thylakoid Membrane

1977 ◽  
Vol 32 (3-4) ◽  
pp. 271-280 ◽  
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.

Further evidence for the existence of cyclic and non-cyclic photophosphorylation in vivo by means of desaspidin and DCMU

1967 ◽  
Vol 22 (5) ◽  
pp. 537-540 ◽  
Author(s):  
W. Urbach ◽  
W. Simonis
Keyword(s):  
Antimycin A ◽  
Anaerobic Conditions ◽  
Intact Cells ◽  
Cyclic Photophosphorylation ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions

The effect of desaspidin and DCMU on photophosphorylation in intact cells under aerobic and anaerobic conditions has been studied. Desaspidin is mainly effective in N2 and inhibits under these conditions the DCMU-insensitive cyclic photophosphorylation in vivo like antimycin A. The inhibition of the phosphorylation in light by DCMU is stronger in N2 than in air which suggests a partial existence of oxydative phosphorylation during illumination.

Effects of 3,5-dibromo-4-hydroxybenzaldehyde O-(2,4-dinitrophenyl)oxime on Reactions of Mitochondria and Chloroplasts

Weed Science ◽  
1970 ◽  
Vol 18 (3) ◽  
pp. 419-426 ◽  
Author(s):  
D. E. Moreland ◽  
W. J. Blackmon
Keyword(s):  
Electron Transport ◽  
Oxygen Uptake ◽  
Electron Donor ◽  
Spinacia Oleracea ◽  
Herbicidal Activity ◽  
Oxygen Utilization ◽  
White Potato ◽  
Ferricyanide Reduction ◽  
Cyclic Photophosphorylation ◽  
Limited Oxygen

The effects of 3,5-dibromo-4-hydroxybenzaldehyde O-(2,4-dinitrophenyl)oxime (hereinafter referred to as C-9122), 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil), 3,5-dibromo-4-hydroxybenzaldoxime (hereinafter referred to as bromoxime), and 2,4-dinitrophenol (hereinafter referred to as DNP) on phosphorylation and electron transport were measured in mitochondria isolated from white potato tubers (Solarium tuberosum L.) and in chloroplasts from spinach leaves (Spinacia oleracea L.). Mitochondrial oxygen utilization was monitored polarographically. All four chemicals stimulated ADP-limited oxygen utilization, inhibited non-ADP-limited oxygen uptake, and relieved oligomycin-inhibited oxygen uptake. C-9122 produced responses at lower molar concentrations than did bromoxynil, bromoxime, and DNP. The I50 value for inhibition of state 3 respiration by C-9122 was 2.7 × 10−6 M.In chloroplasts, C-9122, bromoxime, and DNP inhibited photoreduction and coupled photophosphorylation with water as the electron donor, and with ferricyanide and NADP as electron acceptors. Cyclic photophosphorylation, with phenazine methosulfate as the electron mediator under an argon gas phase, also was inhibited. With ascorbate-2,6-dichlorophenolindophenol (hereinafter referred to as DPIP) as the electron donor, phosphorylation coupled to NADP reduction was inhibited, but not the reduction of NADP. C-9122 was the strongest inhibitor, and bromoxime was the weakest inhibitor of the several reactions. The I50 value for inhibition of the coupled ferricyanide reduction was 4.6 × 10−6 M for C-9122. C-9122 appeared to act in two different ways by (a) inhibiting electron transport at or near photosystem II and the oxygen evolution pathway, and (b) interfering with energy transfer and the generation of ATP. Bromoxynil inhibited photoreduction and photophosphorylation reactions in which water served as the electron donor; but it was a very poor inhibitor of both cyclic photophosphorylation, and photophosphorylation coupled to NADP reduction with ascorbate-DPIP serving as the electron donor. Because of the pivotal role of ATP in cellular metabolism, it is conceivable that interference with ATP generation could be a major (but not necessarily the only) mechanism through which the herbicidal activity of C-9122 is expressed.

Localization and Orientation of Subunit Delta of Spinach Chloroplast ATP-Synthase within the CF0CF1 Complex. 1. Distinction of Shielded and Exposed Surfaces of Delta on the Thylakoid Membrane

1989 ◽  
Vol 44 (1-2) ◽  
pp. 153-160 ◽  
Author(s):  
Richard J. Berzborn ◽  
Werner Finke
Keyword(s):  
Staphylococcus Aureus ◽  
Atp Synthase ◽  
Thylakoid Membrane ◽  
Quaternary Structure ◽  
Large Degree ◽  
Polyclonal Antiserum ◽  
Spinach Chloroplast ◽  
Cyclic Photophosphorylation ◽  
Exposed Part

Abstract A new polyclonal antiserum against spinach CF1 subunit delta was produced in rabbits. It decorates only one band at 21 kDa in Western immunoblots of thylakoid proteins and does not react in ELISA with δ-free four subunit CF1 (-δ); therefore it is regarded monospecific. The polypeptide used as immunogen had been purified by HPLC. Earlier antisera against CF1 δ crossreact with CF1 subunit β. The new antiserum 306 contains different antibodies; some can be absorbed with thylakoids, i.e. by δ within the assembled CF0CF1 complex on the membrane, others still react in ELISA with isolated CF1. The former antibodies agglutinate thylakoids and inhibit PMS cyclic photophosphorylation. Therefore we conclude that part of the surface of CF1 subunit δ is exposed within the quaternary structure of the ATP-synthase complex of photosynthetically active thylakoids, but part of the surface of δ is shielded. Trypsination of isolated δ occurs at several sites, but this protease does not attack δ in situ, nor does aminopeptidase. Staphylococcus aureus protease V8 digests CF1 δ after isolation at residues Asp53, Glu61, Glu95 and Glu106, but has no access to these residues of δ in situ. Thus CF1 subunit δ seems to be shielded within the CF0CF1 complex to a large degree. Direct agglutination of thylakoids by anti δ serum 306 was weak and could be improved tenfold by a Coombs serum (goat anti rabbit gammaglobulin), whereas an anti β serum agglutinated directly. From this we conclude that δ is not accessible at the top of the enzyme; the exposed part is extending below the large subunits a and β and oriented towards the membrane.

Mechanism of Action of the Herbicide 4,6-Dinitro-o-cresol in Photosynthesis

1979 ◽  
Vol 34 (11) ◽  
pp. 1021-1023 ◽  
Author(s):  
J. J. S. van Rensen ◽  
J. H. Hobé
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Mechanism Of Action ◽  
Chemical Structure ◽  
Methyl Viologen ◽  
Primary Electron ◽  
Reaction Centers ◽  
Mehler Reaction ◽  
Cyclic Photophosphorylation ◽  
Primary Electron Acceptor

Abstract The herbicide 4,6-dinitro-o-cresol inhibits electron transport to ferricyanide and non-cyclic photophosphorylation for 50% at about 15 μm. At higher concentrations the photosystem I depen­dent Mehler reaction ascorbate/dichlorophenolindophenol to methyl viologen is stimulated, while cyclic photophosphorylation is inhibited. The herbicide thus is an inhibitory uncoupler. Although the chemical structure of 4,6-dinitro-o-cresol is different from that of the diuron-type herbicides, its site and mechanism of action is similar. Both 4,6-dinitro-o-cresol and diuron inhibit electron transport between the primary electron acceptor of Photosystem II and the plastoquinone pool. This causes a closing of the reaction centers of Photosystem II. The interaction with the inhibited molecule however is different for the two herbicides.

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