Stoichiometry of proton movements coupled to ATP synthesis driven by a pH gradient inStreptococcus lactis

1982 ◽  
Vol 66 (1) ◽  
pp. 63-75 ◽  
Author(s):  
Peter C. Maloney ◽  
F. C. Hansen
Keyword(s):  
Atp Synthesis ◽  
Ph Gradient

Mitochondrial transmembrane potential and pH gradient during anoxia

1987 ◽  
Vol 252 (4) ◽  
pp. C349-C355 ◽  
Author(s):  
B. S. Andersson ◽  
T. Y. Aw ◽  
D. P. Jones
Keyword(s):  
Transmembrane Potential ◽  
Adenine Nucleotide ◽  
Electron Flow ◽  
Atp Synthesis ◽  
Isolated Hepatocytes ◽  
Mitochondrial Transmembrane Potential ◽  
Ph Gradient ◽  
Protonmotive Force ◽  
Ion Distribution ◽  
Cytosolic Ph

The effect of anoxia on the mitochondrial transmembrane potential and pH gradient was studied in a preparation of isolated hepatocytes. Transmembrane potential (delta psi) was calculated from the distribution of triphenylmethylphosphonium between the mitochondrial, cytosolic, and extracellular compartments, which were separated by digitonin fractionation and centrifugation. Mitochondrial and cytosolic pH values were calculated from the distribution of the weak acid, dimethadione, which was determined similarly. After 30 min anoxia, the magnitude of mitochondrial delta psi was decreased from -163 to -133 mV and the delta pH (mitochondria vs. cytoplasm) was essentially unchanged (aerobic, 0.78 +/- 0.08; anaerobic, 0.76 +/- 0.11). Thus the protonmotive force (delta p = delta psi-Z delta pH), is largely retained even in the absence of electron flow and ATP synthesis. Inhibitors of the ATP synthase (oligomycin), mitochondrial adenine nucleotide carrier (atractyloside), and glycolytic pathway (2-deoxy-D-glucose) do not affect the ability of the cell to maintain delta psi during anoxia. Therefore, the results indicate that retention of the protonmotive force is not due to utilization of ATP produced by glycolysis and suggest that mechanisms exist to preserve ion distribution during anoxia.

scholarly journals The protonmotive force in bovine heart submitochondrial particles. Magnitude, sites of generation and comparison with the phosphorylation potential

1978 ◽  
Vol 174 (1) ◽  
pp. 237-256 ◽  
Author(s):  
M C Sorgato ◽  
S J Ferguson ◽  
D B Kell ◽  
P John
Keyword(s):  
Membrane Potential ◽  
Reaction Medium ◽  
Atp Synthesis ◽  
Ph Gradient ◽  
Protonmotive Force ◽  
Submitochondrial Particles ◽  
Electron Mediator ◽  
Phosphorylation Potential ◽  
Bovine Heart ◽  
Gradient Component

1. The magnitude of the protonmotive force in respiring bovine heart submitochondrial particles was estimated. The membrane-potential component was determined from the uptake of S14CN-ions, and the 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 approx. 145mV and the pH gradient was between 0 and 0.5 unit when the particles were suspended in a Pi/Tris reaction medium. The addition of the permeant NO3-ion decreased the membrane potential with a corresponding increase in the pH gradient. In a medium containing 200mM-sucrose, 50mM-KCl and Hepes as buffer, the total protonmotive force was 185mV, comprising a membrane potential of 90mV and a pH gradient of 1.6 units. Thus the protonmotive force was slightly larger in the high-osmolarity medium. 3. The phosphorylation potential (= deltaG0′ + RT ln[ATP]/[ADP][Pi]) was approx. 43.1 kJ/mol (10.3kcal/mol) in all the reaction media tested. Comparison of this value with the protonmotive force indicates that more than 2 and up to 3 protons must be moved across the membrane for each molecule of ATP synthesized by a chemiosmotic mechanism. 4. Succinate generated both a protonmotive force and a phosphorylation potential that were of similar magnitude to those observed with NADH as substrate. 5. Although oxidation of NADH supports a rate of ATP synthesis that is approximately twice that observed with succinate, respiration with either of these substrates generated a very similar protonmotive force. Thus there seemed to be no strict relation between the size of the protonmotive force and the phosphorylation rate. 6. In the presence of antimycin and/or 2-n-heptyl-4-hydroxyquinoline N-oxide, ascorbate oxidation with either NNN'N′-tetramethyl-p-phenylenediamine or 2,3,5,6-tetramethyl-p-phenylenediamine as electron mediator generated a membrane potential of approx. 90mV, but no pH gradient was detected, even in the presence of NO3-. These data are discussed with reference to the proposal that cytochrome oxidase contains a proton pump.

ATP-SYNTHESIS INDUCED BY A pH-GRADIENT IMPOSED ACROSS A COLLAGEN FILM BEARING AN ATPase-ATPSYNTHASE

1978 ◽  
pp. 459-466
Author(s):  
Catherine Godinot ◽  
Bruno Blanchy ◽  
Pierre R. Coulet ◽  
Danièle C. Gautheron
Keyword(s):  
Atp Synthesis ◽  
Ph Gradient ◽  
Collagen Film

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.

Effects of Neuroactive Amino Acids Derivatives on Cardiac and Cerebral Mitochondria and Endothelial functions in Animals Exposed to Stress

2017 ◽  
Vol 2 (2) ◽  
pp. 34
Author(s):  
TA Popova ◽  
II Prokofiev ◽  
IS Mokrousov ◽  
Valentina Perfilova ◽  
AV Borisov ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Platelet Aggregation ◽  
Atp Synthesis ◽  
Elevated Concentration ◽  
Blood Pressure Monitor ◽  
Pressure Monitor ◽  
Griess Reagent ◽  
Arterial Blood ◽  
Endothelial Functions

Introduction: To study the effects of glufimet, a new derivative of glutamic acid, and phenibut, a derivative of γ-aminobutyric acid (GABA), on cardiac and cerebral mitochondria and endothelial functions in animals following exposure to stress and inducible nitric oxide synthase (iNOS) inhibition. Methods: Rats suspended by their dorsal cervical skin fold for 24 hours served as the immobilization and pain stress model. Arterial blood pressure was determined using a non-invasive blood pressure monitor. Mitochondrial fraction of heart and brain homogenates were isolated by differential centrifugation and analysed for mitochondrial respiration intensity, lipid peroxidation (LPO) and antioxidant enzyme activity using polarographic method. The concentrations of nitric oxide (NO) terminal metabolites were measured using Griess reagent. Hemostasis indices were evaluated. Platelet aggregation was estimated using modified version of the Born method described by Gabbasov et al., 1989. Results: The present study demonstrated that stress leads to an elevated concentration of NO terminal metabolites and LPO products, decreased activity of antioxidant enzymes, reduced mitochondrial respiratory function, and endothelial dysfunction. Inhibition of iNOS by aminoguanidine had a protective effect. Phenibut and glufimet inhibited a rise in stress-induced nitric oxide production. This resulted in enhanced coupling of substrate peroxidation and ATP synthesis. The reduced LPO processes caused by glufimet and phenibut normalized the endothelial function which was proved by the absence of average daily blood pressure (BP) elevation episodes and a significant increase in platelet aggregation level. Conclusion: Glufimet and phenibut restrict the harmful effects of stress on the heart and brain possibly by modulating iNOS activity.

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