The puzzle of high phosphorylation potential and low protonmotive force generated by oxidative phosphorylation in Paracoccus denitrificans membrane vesicles in the presence of nitrate

1984 ◽  
Vol 12 (3) ◽  
pp. 456-456 ◽  
Author(s):  
DEREK PARSONAGE ◽  
STUART J. FERGUSON
Keyword(s):  
Oxidative Phosphorylation ◽  
Paracoccus Denitrificans ◽  
Membrane Vesicles ◽  
Protonmotive Force ◽  
Phosphorylation Potential

scholarly journals The protonmotive force in phosphorylating membrane vesicles from Paracoccus denitrificans. Magnitude, sites of generation and comparison with the phosphorylation potential

1978 ◽  
Vol 174 (1) ◽  
pp. 257-266 ◽  
Author(s):  
Douglas B. Kell ◽  
Philip John ◽  
Stuart J. Ferguson
Keyword(s):  
Membrane Potential ◽  
Paracoccus Denitrificans ◽  
Atp Synthesis ◽  
Membrane Vesicles ◽  
Energy Coupling ◽  
Ph Gradient ◽  
Protonmotive Force ◽  
Electron Mediator ◽  
Succinate Oxidation ◽  
Phosphorylation Potential

1. The magnitude of the protonmotive force in phosphorylating membrane vesicles from Paracoccus denitrificans was estimated. The membrane potential component was determined from the uptake of S14CN−, and the transmembrane pH gradient component from the uptake of [14C]methylamine. In each case a flow-dialysis technique was used to monitor uptake. 2. With NADH as substrate, the membrane potential was about 145mV and the pH gradient was below 0.5 pH unit. The membrane potential was decreased by approx. 15mV during ATP synthesis, and was abolished on addition of carbonyl cyanide p-trifluoromethoxyphenylhydrazone. In the presence of KCl plus valinomycin the membrane potential was replaced by a pH gradient of 1.5 units. 3. Succinate oxidation generated a membrane potential of approx. 125mV and the pH gradient was below 0.5 pH unit. Oxidation of ascorbate (in the presence of antimycin) with either 2,3,5,6-tetramethyl-p-phenylenediamine or NNN′N′-tetramethyl-p-phenylenediamine as electron mediator usually generated a membrane potential of approx. 90mV. On occasion, ascorbate oxidation did not generate a membrane potential, suggesting that the presence of a third energy-coupling site in P. denitrificans vesicles is variable. 4. With NADH or succinate as substrate, the phosphorylation potential (ΔGp=ΔG0′+RTln[ATP]/ [ADP][Pi]) was approx. 53.6kJ/mol (12.8kcal/mol). Comparison of this value with the protonmotive force indicates that more than 3 protons need to be translocated via the adenosine triphosphatase of P. denitrificans for each molecule of ATP synthesized by a chemiosmotic mechanism. In the presence of 10mm-KNO3 the protonmotive force was not detectable (<60mV) but ΔGp was not altered. This result may indicate either that there is no relationship between the protonmotive force and ΔGp, or that for an unidentified reason the equilibration of SCN− or methylamine with the membrane potential and the pH gradient is prevented by NO3− in this system.

scholarly journals Molecular and Supramolecular Structure of the Mitochondrial Oxidative Phosphorylation System: Implications for Pathology

Life ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 242
Author(s):  
Salvatore Nesci ◽  
Fabiana Trombetti ◽  
Alessandra Pagliarani ◽  
Vittoria Ventrella ◽  
Cristina Algieri ◽  
...  
Keyword(s):  
Oxidative Phosphorylation ◽  
Atp Synthase ◽  
Mitochondrial Permeability Transition ◽  
Ros Generation ◽  
Protonmotive Force ◽  
Mitochondrial Oxidative Phosphorylation ◽  
F1fo Atp Synthase ◽  
Functional Changes ◽  
Age Related ◽  
Mitochondrial Functions

Under aerobic conditions, mitochondrial oxidative phosphorylation (OXPHOS) converts the energy released by nutrient oxidation into ATP, the currency of living organisms. The whole biochemical machinery is hosted by the inner mitochondrial membrane (mtIM) where the protonmotive force built by respiratory complexes, dynamically assembled as super-complexes, allows the F1FO-ATP synthase to make ATP from ADP + Pi. Recently mitochondria emerged not only as cell powerhouses, but also as signaling hubs by way of reactive oxygen species (ROS) production. However, when ROS removal systems and/or OXPHOS constituents are defective, the physiological ROS generation can cause ROS imbalance and oxidative stress, which in turn damages cell components. Moreover, the morphology of mitochondria rules cell fate and the formation of the mitochondrial permeability transition pore in the mtIM, which, most likely with the F1FO-ATP synthase contribution, permeabilizes mitochondria and leads to cell death. As the multiple mitochondrial functions are mutually interconnected, changes in protein composition by mutations or in supercomplex assembly and/or in membrane structures often generate a dysfunctional cascade and lead to life-incompatible diseases or severe syndromes. The known structural/functional changes in mitochondrial proteins and structures, which impact mitochondrial bioenergetics because of an impaired or defective energy transduction system, here reviewed, constitute the main biochemical damage in a variety of genetic and age-related diseases.

scholarly journals PS1014 GLYCOLYSIS VERSUS OXIDATIVE PHOSPHORYLATION – POTENTIAL THERAPEUTIC TARGETS IN AML

HemaSphere ◽  
2019 ◽  
Vol 3 (S1) ◽  
pp. 456-457
Author(s):  
B. Lapa ◽  
J. Jorge ◽  
R.S. Alves ◽  
A.S. Pires ◽  
A.M. Abrantes ◽  
...  
Keyword(s):  
Oxidative Phosphorylation ◽  
Therapeutic Targets ◽  
Phosphorylation Potential

scholarly journals The association of proton movement with galactose transport into subcellular membrane vesicles of Escherichia coli

1983 ◽  
Vol 210 (3) ◽  
pp. 699-705 ◽  
Author(s):  
P Horne ◽  
P J F Henderson
Keyword(s):  
Escherichia Coli ◽  
Transport System ◽  
Direct Evidence ◽  
Membrane Vesicles ◽  
Protonmotive Force ◽  
Ph Values ◽  
Subcellular Membrane ◽  
System 2 ◽  
Galactose Transport ◽  
Proton Movement

1. Subcellular membrane vesicles were prepared from a strain of Escherichia coli constitutive for the GalP galactose-transport system. 2. The addition of substrates of the GalP transport system to vesicle suspensions promoted alkaline pH changes, which provided direct evidence for the coupling of sugar and proton transport. 3. Respiration-energized galactose transport was progressively inhibited at pH values above 6.0, and was abolished by agents that render the membrane permeable to protons. 4. The combined effects of valinomycin, the nigericin-like compound A217 and pH on galactose transport suggested that both delta pH and delta psi components of the protonmotive force contributed to energization of galactose transport. 5. These results substantiate the conclusion that the GalP transport system operates by a chemiosmotic mechanism.

scholarly journals The oxidative activities of membrane vesicles from Bacillus caldolyticus. Energy-dependence of succinate oxidation

1978 ◽  
Vol 170 (2) ◽  
pp. 395-405 ◽  
Author(s):  
Anthony G. Dawson ◽  
J. B. Chappell
Keyword(s):  
Cytochrome C ◽  
Succinate Dehydrogenase ◽  
Cytochrome B ◽  
Atp Hydrolysis ◽  
Membrane Vesicles ◽  
Protonmotive Force ◽  
Anaerobic Conditions ◽  
Succinate Oxidation ◽  
Ample Supply ◽  
Energy Conserving

1. The properties of membrane vesicles from the extreme thermophile Bacillus caldolyticus were investigated. 2. Vesicles prepared by exposure of spheroplasts to ultrasound contained cytochromes a, b and c, and at 50°C they rapidly oxidized NADH and ascorbate in the presence of tetramethyl-p-phenylenediamine. Succinate and l-malate were oxidized more slowly, and dl-lactate, l-alanine and glycerol 1-phosphate were not oxidized. 3. In the absence of proton-conducting uncouplers the oxidation of NADH was accompanied by a net translocation of H+ into the vesicles. Hydrolysis of ATP by a dicyclohexylcarbodi-imide-sensitive adenosine triphosphatase was accompanied by a similarly directed net translocation of H+. 4. Uncouplers (carbonyl cyanide p-trifluoromethoxyphenylhydrazone or valinomycin plus NH4+) prevented net H+ translocation but stimulated ATP hydrolysis, NADH oxidation and ascorbate oxidation. The last result suggested an energy-conserving site in the respiratory chain between cytochrome c and oxygen. 5. Under anaerobic conditions the reduction of cytochrome b by ascorbate (with tetramethyl-p-phenylenediamine) was stimulated by ATP hydrolysis, indicating an energy-conserving site between cytochrome b and cytochrome c. However, no reduction of NAD+ supported by oxidation of succinate, malate or ascorbate occurred, neither did it with these substrates in the presence of ATP under anaerobic conditions, suggesting that there was no energy-conserving site between NADH and cytochrome b. 6. Succinate oxidation, in contrast with that of NADH and ascorbate, was strongly inhibited by uncouplers and stimulated by ATP hydrolysis. These effects were not observed when phenazine methosulphate, which transfers electrons from succinate dehydrogenase directly to oxygen, was present. It was concluded that in these vesicles the oxidation of succinate was energy-dependent and that the reoxidation of reduced succinate dehydrogenase was dependent on the outward movement of H+ by the protonmotive force. 7. In support of the foregoing conclusion it was shown that the reduction of fumarate by NADH was an energy-conserving process. 8. If the activities of vesicles accurately represent those of the intact organism it appears that in B. caldolyticus the reduction of fumarate to succinate at the expense of reducing equivalents from NADH is energetically favoured over succinate oxidation even under aerobic conditions. This may be related to the need for an ample supply of succinate for haem synthesis in order to provide cytochromes for the organism.

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