Localized energy coupling during photophosphorylation by chromatophores of Rhodopseudomonas capsulata N22

1982 ◽  
Vol 2 (10) ◽  
pp. 743-749 ◽  
Author(s):  
G. Duncan Hitchens ◽  
Douglas B. Kell
Keyword(s):  
Free Energy ◽  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Energy Coupling ◽  
Rhodopseudomonas Capsulata ◽  
Titration Method ◽  
Dual Inhibitor ◽  
Transport Chain ◽  
Synthase Inhibitor

The principle of the dual inhibitor titration method for testing models of electron-transport phosphorylation is outlined, and the method is applied to the study of photophosphorylation in bacterial chromatophores. It is concluded that energy coupling is strictly localized in nature in this system, in the sense that free energy released by a particular electron-transport chain may be used only by a particular H+-ATP synthase. Dual inhibitor titrations using the uncoupler SF 6847 and the H+-ATP synthase inhibitor oligomycin indicate that uncouplers act by shuttling rapidly between the localized energy-coupling sites.

scholarly journals On the extent of localization of the energized membrane state in chromatophores from Rhodopseudomonas capsulata N22

1982 ◽  
Vol 206 (2) ◽  
pp. 351-357 ◽  
Author(s):  
G D Hitchens ◽  
D B Kell
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Relative Number ◽  
Coupling Model ◽  
Rhodopseudomonas Capsulata ◽  
Apparent Paradox ◽  
Model Free ◽  
Transport Chain ◽  
Chemiosmotic Coupling

1. The principle of the double-inhibitor titration method for assessing competing models of electron transport phosphorylation is expounded. 2. This principle is applied to photophosphorylation by chromatophores from Rhodopseudomonas capsulata N22. 3. It is found that, in contrast to the predictions of the chemiosmotic coupling model, free energy transfer is confined to individual electron transport chain and ATP synthase complexes. 4. This conclusion is not weakened by arguments concerning, the degree of uncoupling in the native chromatophore preparation or the relative number of electron transport chain and ATP synthase complexes present. 5. Photophosphorylation is completely inhibited by the uncoupler SF 6847 at a concentration corresponding to 0.31 molecules per electron transport chain. 6. The apparent paradox is solved by the proposal, consistent with the available evidence on the mode of action of uncouplers, that uncoupler binding causes a co-operative conformation transition in the chromatophore membrane, which leads to uncoupling and which is not present in the absence of uncoupler.

scholarly journals Uncouplers can shuttle between localized energy-coupling sites during photophosphorylation by chromatophores of Rhodopseudomonas capsulata N22

1983 ◽  
Vol 212 (1) ◽  
pp. 25-30 ◽  
Author(s):  
G D Hitchens ◽  
D B Kell
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Electron Flow ◽  
Energy Coupling ◽  
Turnover Time ◽  
Rhodopseudomonas Capsulata ◽  
Antimycin A ◽  
Set Up ◽  
Synthase Inhibitor ◽  
Chromatophore Membrane

Two models of the action of uncoupler molecules in inhibiting photophosphorylation in bacterial chromatophores are considered: either uncoupler molecules shuttle rapidly between energy-coupling sites, or uncoupler molecules that are bound to particular sites in the chromatophores for a time that is comparable with the turnover time of the photophosphorylation apparatus may uncouple by a co-operative ‘substoichiometric’ mechanism. It is found that the titre of uncoupler necessary to cause complete uncoupling is lowered if the rate of photophosphorylation is initially decreased by partially restricting electron flow with an appropriate titre of antimycin A. This result indicates that uncoupler molecules shuttle rapidly between energy coupling in which the energized intermediate between electron transport and phosphorylation is delocalized over the entire chromatophore membrane and those in which it is not. If the rate of photophosphorylation is partially restricted with the covalent H+-translocating ATP synthase inhibitor dicyclohexylcarbodi-imide, the titre of uncoupler necessary to effect complete inhibition of photophosphorylation is also decreased relative to that in which the covalent H+-ATP synthase inhibitor is absent. This important result appears to be inconsistent with models of electron-transport phosphorylation in which the ‘energized state’ of the chromatophore membrane that is set up by electron transport and utilized in photophosphorylation is delocalized over the entire chromatophore membrane.

Functional Expression of Electron Transport Chain and FoF1-ATP Synthase in Optic Nerve Myelin Sheath

2015 ◽  
Vol 40 (11) ◽  
pp. 2230-2241 ◽  
Author(s):  
Martina Bartolucci ◽  
Silvia Ravera ◽  
Greta Garbarino ◽  
Paola Ramoino ◽  
Sara Ferrando ◽  
...  
Keyword(s):  
Electron Transport ◽  
Optic Nerve ◽  
Atp Synthase ◽  
Myelin Sheath ◽  
Electron Transport Chain ◽  
Functional Expression ◽  
Transport Chain ◽  
Fof1 Atp Synthase

The efficiency and plasticity of mitochondrial energy transduction

2005 ◽  
Vol 33 (5) ◽  
pp. 897-904 ◽  
Author(s):  
M.D. Brand
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Uncoupling Protein ◽  
Coupling Efficiency ◽  
Energy Transduction ◽  
Proton Pumping ◽  
Complex Iii ◽  
Proton Pumps ◽  
Transport Chain

Since it was first realized that biological energy transduction involves oxygen and ATP, opinions about the amount of ATP made per oxygen consumed have continually evolved. The coupling efficiency is crucial because it constrains mechanistic models of the electron-transport chain and ATP synthase, and underpins the physiology and ecology of how organisms prosper in a thermodynamically hostile environment. Mechanistically, we have a good model of proton pumping by complex III of the electron-transport chain and a reasonable understanding of complex IV and the ATP synthase, but remain ignorant about complex I. Energy transduction is plastic: coupling efficiency can vary. Whether this occurs physiologically by molecular slipping in the proton pumps remains controversial. However, the membrane clearly leaks protons, decreasing the energy funnelled into ATP synthesis. Up to 20% of the basal metabolic rate may be used to drive this basal leak. In addition, UCP1 (uncoupling protein 1) is used in specialized tissues to uncouple oxidative phosphorylation, causing adaptive thermogenesis. Other UCPs can also uncouple, but are tightly regulated; they may function to decrease coupling efficiency and so attenuate mitochondrial radical production. UCPs may also integrate inputs from different fuels in pancreatic β-cells and modulate insulin secretion. They are exciting potential targets for treatment of obesity, cachexia, aging and diabetes.

scholarly journals Functional characterization of mutants deficient in N-terminal phosphorylation of the CF1 subunit beta

2021 ◽  
Author(s):  
Ralph Bock ◽  
Deserah D Strand ◽  
Daniel Karcher ◽  
Stephanie Ruf ◽  
Anne Schadach ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Atp Hydrolysis ◽  
Molecular Motor ◽  
Functional Characterization ◽  
Phosphorylation Sites ◽  
Transport Chain

Understanding the regulation of photosynthetic light harvesting and electron transfer is of great importance to efforts to improve the ability of the electron transport chain to supply downstream metabolism. The central regulator of the electron transport chain is the ATP synthase, the molecular motor that harnesses the chemiosmotic potential generated from proton coupled electron transport to synthesize ATP. The ATP synthase is regulated both thermodynamically and post-translationally, with proposed phosphorylation sites on multiple subunits. In this study we focused on two N-terminal serines on the catalytic subunit beta, previously proposed to be important for dark inactivation of the complex to avoid ATP hydrolysis at night. Here we show that there is no clear role for phosphorylation in the dark inactivation of ATP synthase. Instead, mutation of one of the two phosphorylated serine residues to aspartate strongly decreased ATP synthase abundance. We propose that the loss of N-terminal phosphorylation of ATP beta may be involved in proper ATP synthase accumulation during complex assembly.

scholarly journals Energy coupling sites in the electron transport chain ofZymomonas mobilis

1995 ◽  
Vol 133 (1-2) ◽  
pp. 99-104 ◽  
Author(s):  
U. Kalnenieks ◽  
N. Galinina ◽  
I. Irbe ◽  
M. Toma
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Energy Coupling ◽  
Transport Chain

scholarly journals Regulation of COX Assembly and Function by Twin CX9C Proteins—Implications for Human Disease

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 197
Author(s):  
Stephanie Gladyck ◽  
Siddhesh Aras ◽  
Maik Hüttemann ◽  
Lawrence I. Grossman
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Atp Synthase ◽  
Protein Interactions ◽  
Human Disease ◽  
Electron Transport Chain ◽  
Intermembrane Space ◽  
Protein Protein Interactions ◽  
Inner Mitochondrial Membrane ◽  
Transport Chain

Oxidative phosphorylation is a tightly regulated process in mammals that takes place in and across the inner mitochondrial membrane and consists of the electron transport chain and ATP synthase. Complex IV, or cytochrome c oxidase (COX), is the terminal enzyme of the electron transport chain, responsible for accepting electrons from cytochrome c, pumping protons to contribute to the gradient utilized by ATP synthase to produce ATP, and reducing oxygen to water. As such, COX is tightly regulated through numerous mechanisms including protein–protein interactions. The twin CX9C family of proteins has recently been shown to be involved in COX regulation by assisting with complex assembly, biogenesis, and activity. The twin CX9C motif allows for the import of these proteins into the intermembrane space of the mitochondria using the redox import machinery of Mia40/CHCHD4. Studies have shown that knockdown of the proteins discussed in this review results in decreased or completely deficient aerobic respiration in experimental models ranging from yeast to human cells, as the proteins are conserved across species. This article highlights and discusses the importance of COX regulation by twin CX9C proteins in the mitochondria via COX assembly and control of its activity through protein–protein interactions, which is further modulated by cell signaling pathways. Interestingly, select members of the CX9C protein family, including MNRR1 and CHCHD10, show a novel feature in that they not only localize to the mitochondria but also to the nucleus, where they mediate oxygen- and stress-induced transcriptional regulation, opening a new view of mitochondrial-nuclear crosstalk and its involvement in human disease.

A regulatory effect of the electron-transport chain on ATP synthase

1986 ◽  
Vol 14 (1) ◽  
pp. 33-33
Author(s):  
BERNHARD HUCHZERMEYER ◽  
EVA HEINRICH
Keyword(s):  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Regulatory Effect ◽  
Transport Chain
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