Site of Action of 2,5-Dimethoxy-3,6-Dichloro-p-Benzoquinone in the Photosynthetic Electron Transport Chain

1981 ◽  
Vol 36 (7-8) ◽  
pp. 656-661 ◽  
Author(s):  
G. Sarojini ◽  
H. Daniell
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Transport Chain ◽  
Electron Transport Rate ◽  
Electron Flow ◽  
Electron Acceptors ◽  
Hill Reaction ◽  
Transport Chain ◽  
Site Of Action ◽  
The Hill

Abstract Electron Acceptors, Photosystem II, Quinones and Quinonediamines Dichlorodimethoxy-/?-benzoquinone (DCDMQ) was tested for its site of action in the photo­ synthetic electron transport chain. Hill reaction mediated by DCDMQ was insensitive to DBMIB (1 nm) but sensitive to DCMU, suggesting its site of action before plastoquinone but after Q -the primary electron acceptor of photosystem II. Extraction of freeze-dried chloroplasts with heptane and analyzing their capacity to photo-oxidize water using various Hill oxidants revealed that silicomolybdate (SiMO) and DCDMQ could effectively restore the activity. Diaminodurene (DAD) in the presence of ferricyanide could restore 40% of the activity. But ferricyanide alone failed to restore the ability to photo-oxidize water in heptane extracted chloroplasts. Similarly, N a2S 0 3 which is known to cause a bottleneck in the electron flow at plastoquinone affected the ferricyanide Hill reaction. Hill reactions mediated by SiMO and DCDMQ were insensitive to the addition of Na2SO3, suggesting that both these oxidants intercept electrons before plastoquinone. But 50% of the activity was lost when sulfite was added to the Hill reaction mediated by DADox. DNP-INT, melittin and picrylhydrazyl were recently introduced as photosystem II inhibitors inhibiting the electron flow between Q and the PQ pool. While DCBQ and DCDMQ Hill reactions were insensitive to DNP-INT, ferricyanide was highly sensitive. The quinonediamines TMPD and DADox showed 50% decrease in the electron transport rate, similar to heptane extracted or sulfite inhibited chloroplasts. Melittin increased the electron transport rate when ferricyanide or TMPD was the Hill oxidant, while DCBQ and DCDMQ reduction remained unaffected. However, DADox Hill reaction showed 50% inhibition in the presence of melittin. Picrylhydrazyl - which inhibits the electron flow between Q and the PQ pool - inhibited the Hill reaction of all the PS II electron acceptors except that of DCDMQ. It is possible that there is another site of intercepting electrons between Q and plastoquinone before the site where most of the quinonediamines accept electrons.

Interaction of Photosystem II Herbicides with Bicarbonate and Formate in Their Effects on Photosynthetic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 374-377 ◽  
Author(s):  
J. J. S. van Rensen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
Amaranthus Hybridus ◽  
Apparent Affinity ◽  
Photosynthetic Electron Flow ◽  
Different Characteristics ◽  
The Hill

The reactivation of the Hill reaction in CO2-depleted broken chloroplasts by various concentrations of bicarbonate was measured in the absence and in the presence of photosystem II herbicides. It appears that these herbicides decrease the apparent affinity of the thylakoid membrane for bicarbonate. Different characteristics of bicarbonate binding were observed in chloroplasts of triazine-resistant Amaranthus hybridus compared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Qв-protein and their interference with photosynthetic electron transport.

Effect of an Antiserum to a Thylakoid Membrane Polypeptide on the Primary Photoreaction of Photosystem II

1976 ◽  
Vol 31 (9-10) ◽  
pp. 594-600 ◽  
Author(s):  
Georg H. Schmid ◽  
Gernot Renger ◽  
Michael Gläser ◽  
Friederike Koenig ◽  
Alfons Radunz ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Electron Flow ◽  
Primary Electron ◽  
Hill Reaction ◽  
Ps Ii ◽  
Absorption Change ◽  
Oxygen Evolving ◽  
The Hill

Abstract As was described previously, an antiserum to polypeptide 11000 inhibited photosynthetic elec­tron transport on the oxygen evolving side of photosystem II. The effect of the antiserum on chloro­plasts from two tobacco mutants also clearly showed that the inhibition site is on the photosystem II-side of the electron transport chain. One of the two tobacco mutants lades the oxygen evolving capacity but exhibits some electron transport with tetramethyl benzidine, an artificial donor to PS II. In this mutant electron transport was barely inhibited. The effect of the antiserum on the primary photoevents showed that the initial amplitude of the absorption change of chlorophyll an at 690 nm and that of the primary electron acceptor X320 at 334 nm both diminished in the presence of the antiserum. Both signals were restored upon addition of diphenylcarbazide another artificial donor to photosystem II. Comparison of the degree of inhibition on the amplitudes of the fast and slow components of the 690 nm absorption change with the manometrically measured inhibition of electron transport shows that besides a full inactivation of a part of the reaction centers of photosystem II another part apparently mediates a fast cyclic electron flow around photosystem II as reported by Renger and Wolff earlier for tris-treated chloroplasts. Moreover, the antiserum affects the low temperature fluorescence in a way which is opposite to Murata’s effect of the Mg2+ -ion induced inhibition of energy spill-over from photosystem II to photosystem I. The antiserum under the condition in which the Hill reaction is inhibited lowered the 686 nm emission and enhanced the 732 nm emission which indicates an enhanced energy spill-over to photosystem I.

Reactions of Antisera to Lutein and Plastoquinone with Chloroplast Preparations and their Effects on Photosynthetic Electron Transport

1973 ◽  
Vol 28 (1-2) ◽  
pp. 36-44 ◽  
Author(s):  
Alfons Radunz ◽  
Georg H. Schmid
Keyword(s):  
Electron Transport ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Potassium Ferricyanide ◽  
Electron Donors ◽  
Hill Reaction ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain ◽  
Pass Through ◽  
The Hill

An antiserum to lutein inhibits photosynthetic electron transport between water and potassium ferricyanide in diloroplasts from green Nicotiana tabacum var. John William’s Breadleaf. However, electron transport between diphenylcarbazide and potassium ferricyanide is not impaired. From this it is concluded that the photochemically active carotenoid should feed its electrons into the photosynthetic electron transport chain before the site from which diphenyl-carbazide donates electrons. The inhibition of the ferricyanide Hill reaction in diloroplasts by antibodies to lutein depends on the accessibility of the carotenoid antigen in the thylakoid membrane. In fresh preparations the accessibility is greater in diloroplasts in which photo- synthetic electron transport is coupled to photophosphorylation. Concomitantly the antiserum to lutein agglutinates only such chloroplast preparations in which the Hill reaction is impaired by the antiserum. An antiserum to plastoquinone inhibits ferricyanide photoreduction of diloroplasts regardless whether driven by water or diphenylcarbazide as the electron donors. Typical photosystem-I-reactions are not influenced by the antiserum. In a certain type of chloroplast preparations the antiserum does not inhibit PMS-mediated photophosphorylation inferring that plastoquinone, eventually involved in this reaction, is either not accessible to antibodies, or that this cyclic electron flow does not necessarily pass through plastoquinone.

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

2020 ◽  
Vol 13 (9) ◽  
pp. 2903-2914 ◽  
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.

scholarly journals Purification of Helicobacter pylori NCTC 11637 Cytochrome bc1 and Respiration with d-Proline as a Substrate

2009 ◽  
Vol 192 (5) ◽  
pp. 1410-1415 ◽  
Author(s):  
Minoru Tanigawa ◽  
Tomomitsu Shinohara ◽  
Katsushi Nishimura ◽  
Kumiko Nagata ◽  
Morio Ishizuka ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Amino Acid ◽  
Electron Transport ◽  
Electron Transport Chain ◽  
Electron Flow ◽  
Gene Clusters ◽  
Acid Dehydrogenase ◽  
Amino Acid Dehydrogenase ◽  
Transport Chain ◽  
H Pylori

ABSTRACT Helicobacter pylori is a microaerophilic bacterium associated with gastric inflammation and peptic ulcers. Knowledge of how pathogenic organisms produce energy is important from a therapeutic point of view. We found d-amino acid dehydrogenase-mediated electron transport from d-proline or d-alanine to oxygen via the respiratory chain in H. pylori. Coupling of the electron transport to ATP synthesis was confirmed by using uncoupler reagents. We reconstituted the electron transport chain to demonstrate the electron flow from the d-amino acids to oxygen using the recombinant cytochrome bc 1 complex, cytochrome c-553, and the terminal oxidase cytochrome cbb 3 complex. Upon addition of the recombinant d-amino acid dehydrogenase and d-proline or d-alanine to the reconstituted electron transport system, reduction of cytochrome cbb 3 and oxygen consumption was revealed spectrophotometrically and polarographically, respectively. Among the constituents of H. pylori's electron transport chain, only the cytochrome bc 1 complex had been remained unpurified. Therefore, we cloned and sequenced the H. pylori NCTC 11637 cytochrome bc 1 gene clusters encoding Rieske Fe-S protein, cytochrome b, and cytochrome c 1, with calculated molecular masses of 18 kDa, 47 kDa, and 32 kDa, respectively, and purified the recombinant monomeric protein complex with a molecular mass of 110 kDa by gel filtration. The absorption spectrum of the recombinant cytochrome bc 1 complex showed an α peak at 561 nm with a shoulder at 552 nm.

Micronutrient homeostasis and chloroplast iron protein expression is largely maintained in a chloroplast copper transporter mutant

2020 ◽  
Vol 47 (12) ◽  
pp. 1041 ◽  
Author(s):  
Gretchen E. Kroh ◽  
Marinus Pilon
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Electron Transport Rate ◽  
Photosynthetic Electron Transport ◽  
Metal Homeostasis ◽  
Transport Rate ◽  
Fe Deficiency ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain ◽  
Cu Homeostasis

PAAI is a P-Type ATPase that functions to import copper (Cu) into the chloroplast. Arabidopsis thaliana (L.) Heynh. paa1 mutants have lowered plastocyanin levels, resulting in a decreased photosynthetic electron transport rate. In nature, iron (Fe) and Cu homeostasis are often linked and it can be envisioned that paa1 acclimates its photosynthetic machinery by adjusting expression of its chloroplast Fe-proteome, but outside of Cu homeostasis paa1 has not been studied. Here, we characterise paa1 ultrastructure and accumulation of electron transport chain proteins in a paa1 allelic series. Furthermore, using hydroponic growth conditions, we characterised metal homeostasis in paa1 with an emphasis on the effects of Fe deficiency. Surprisingly, the paa1 mutation does not affect chloroplast ultrastructure or the accumulation of other photosynthetic electron transport chain proteins, despite the strong decrease in electron transport rate. The regulation of Fe-related photosynthetic electron transport proteins in response to Fe status was maintained in paa1, suggesting that regulation of the chloroplast Fe proteins ignores operational signals from photosynthetic output. The characterisation of paa1 has revealed new insight into the regulation of expression of the photosynthetic electron transport chain proteins and chloroplast metal homeostasis and can help to develop new strategies for the detection of shoot Fe deficiency.

On a new inhibitor of photosynthetic electron-transport in isolated chloroplasts

1970 ◽  
Vol 25 (10) ◽  
pp. 1157-1159 ◽  
Author(s):  
A. Trebst ◽  
E. Harth ◽  
W. Draber
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
High Concentration ◽  
Ferricyanide Reduction ◽  
The Hill ◽  
Photosystem I And Ii ◽  
Isolated Chloroplasts

A halogenated benzoquinone has been found to inhibit the photosynthetic electron transport system in isolated chloroplasts. 2·10-6ᴍ of dibromo-thymoquinone inhibit the Hill- reaction with NADP, methylviologen or anthraquinone to 100%, but do not effect the photoreduction of NADP at the expense of an artificial electron donor. The Hill - reaction with ferricyanide is inhibited even at the high concentration of 2·10-5ᴍ of dibromo-thymoquinone to only 60%. The remaining reduction in the presence of the inhibitor reflects the rate of ferricyanide reduction by photosystem II. It is concluded that the inhibition of electron transport by the quinone occurs between photosystem I and II and close to or at the functional site of plastoquinone.

scholarly journals Tracking Electron Uptake from a Cathode into Shewanella Cells: Implications for Energy Acquisition from Solid-Substrate Electron Donors

mBio ◽  
2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Annette R. Rowe ◽  
Pournami Rajeev ◽  
Abhiney Jain ◽  
Sahand Pirbadian ◽  
Akihiro Okamoto ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Complex I ◽  
Electron Transport Chain ◽  
Electron Flow ◽  
Extracellular Electron Transfer ◽  
Terminal Electron Acceptor ◽  
Cellular Energy ◽  
Transport Chain ◽  
Energy Acquisition

ABSTRACTWhile typically investigated as a microorganism capable of extracellular electron transfer to minerals or anodes,Shewanella oneidensisMR-1 can also facilitate electron flow from a cathode to terminal electron acceptors, such as fumarate or oxygen, thereby providing a model system for a process that has significant environmental and technological implications. This work demonstrates that cathodic electrons enter the electron transport chain ofS. oneidensiswhen oxygen is used as the terminal electron acceptor. The effect of electron transport chain inhibitors suggested that a proton gradient is generated during cathode oxidation, consistent with the higher cellular ATP levels measured in cathode-respiring cells than in controls. Cathode oxidation also correlated with an increase in the cellular redox (NADH/FMNH2) pool determined with a bioluminescence assay, a proton uncoupler, and a mutant of proton-pumping NADH oxidase complex I. This work suggested that the generation of NADH/FMNH2under cathodic conditions was linked to reverse electron flow mediated by complex I. A decrease in cathodic electron uptake was observed in various mutant strains, including those lacking the extracellular electron transfer components necessary for anodic-current generation. While no cell growth was observed under these conditions, here we show that cathode oxidation is linked to cellular energy acquisition, resulting in a quantifiable reduction in the cellular decay rate. This work highlights a potential mechanism for cell survival and/or persistence on cathodes, which might extend to environments where growth and division are severely limited.IMPORTANCEThe majority of our knowledge of the physiology of extracellular electron transfer derives from studies of electrons moving to the exterior of the cell. The physiological mechanisms and/or consequences of the reverse processes are largely uncharacterized. This report demonstrates that when coupled to oxygen reduction, electrode oxidation can result in cellular energy acquisition. This respiratory process has potentially important implications for how microorganisms persist in energy-limited environments, such as reduced sediments under changing redox conditions. From an applied perspective, this work has important implications for microbially catalyzed processes on electrodes, particularly with regard to understanding models of cellular conversion of electrons from cathodes to microbially synthesized products.

scholarly journals Oncogenic pathways and the electron transport chain: a dangeROS liaison

2019 ◽  
Vol 122 (2) ◽  
pp. 168-181 ◽  
Author(s):  
Vittoria Raimondi ◽  
Francesco Ciccarese ◽  
Vincenzo Ciminale
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Electron Flow ◽  
Second Messengers ◽  
Driver Mutations ◽  
Cell Phenotype ◽  
Oxygen Species ◽  
Hallmarks Of Cancer ◽  
Oncogenic Pathways ◽  
Transport Chain

AbstractDriver mutations in oncogenic pathways, rewiring of cellular metabolism and altered ROS homoeostasis are intimately connected hallmarks of cancer. Electrons derived from different metabolic processes are channelled into the mitochondrial electron transport chain (ETC) to fuel the oxidative phosphorylation process. Electrons leaking from the ETC can prematurely react with oxygen, resulting in the generation of reactive oxygen species (ROS). Several signalling pathways are affected by ROS, which act as second messengers controlling cell proliferation and survival. On the other hand, oncogenic pathways hijack the ETC, enhancing its ROS-producing capacity by increasing electron flow or by impinging on the structure and organisation of the ETC. In this review, we focus on the ETC as a source of ROS and its modulation by oncogenic pathways, which generates a vicious cycle that resets ROS levels to a higher homoeostatic set point, sustaining the cancer cell phenotype.

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