PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “ATP Synthetase Complexes”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed2006

Thermal energy and the origin of life.

Life has evolved on Earth with electromagnetic radiation (light), fermentable organic molecules, and oxidizable chemicals as sources of energy. Biological use of thermal energy has not been observed although heat, and the thermal gradients required to convert it into free energy, are ubiquitous and were even more abundant at the time of the origin of life on Earth. Nevertheless, Earth-organisms sense thermal energy, and in suitable environments may have gained the capability to use it as energy source. It has been proposed that the first organisms obtained their energy by a first protein named pF(1) that worked on a thermal variation of the binding change mechanism of today's ATP sythase enzyme. Organisms using thermosynthesis may still live where light or chemical energy sources are not available. Possible suitable examples are subsurface environments on Earth and in the outer Solar System, in particular the subsurface oceans of the icy satellites of Jupiter and Saturn.

ATP Synthetase Complexes↗
PubMed1991

Uncoupling effect of the general anesthetic 2,6-diisopropylphenol in isolated rat liver mitochondria.

2,6-Diisopropylphenol, a general anesthetic, was previously reported to reduce the transmembrane electrical potential in isolated rat liver mitochondria without affecting the rate of ATP production. This effect appeared to contrast with the generally accepted chemiosmotic mechanism for oxidative phosphorylation. In this study we further examined the influence of 2,6-diisopropylphenol on the production of ATP by isolated mitochondria and we studied its effect on the permeability of the inner mitochondrial membrane to protons. In order to clarify the effects of 2,6-diisopropylphenol on mitochondrial ATP production the activities of the adenine nucleotide translocator and the ATP synthetase were evaluated. The results obtained indicate that the depression of the transmembrane electrical potential elicited by 2,6-diisopropylphenol decreased the activity of the ATP synthetase (as expected in the chemiosmotic model for energy coupling), but not that of the adenine nucleotide translocator. The decrease of the ATP synthetase activity, however, did not result in an apparent inhibition of the overall rate of ATP production in isolated mitochondria due to the rate-limiting effect of the adenine nucleotide translocator in this process. Moreover 2,6-diisopropylphenol was found to increase the permeability to protons of the inner mitochondrial membrane; this effect became more marked as the pH of the incubation medium was increased, demonstrating that it involved the dissociated form of 2,6-diisopropylphenol. These observations suggested that 2,6-diisopropylphenol affected oxidative phosphorylation by acting as a mild protonophore and that its effectiveness was limited by the low fraction of phenol dissociated at near-physiological pH.

ATP Synthetase Complexes↗
PubMed1983

Impairment of liver regeneration during inhibition of mitochondrial protein synthesis by oxytetracycline.

Under standard conditions, liver regeneration is impaired if mitochondrial protein synthesis is completely blocked. By treating rats with oxytetracycline for various periods of time directly prior to partial hepatectomy, livers were led to a condition of relative deficiency in cytochrome c oxidase and ATP synthetase. To this end, oxytetracycline was administered by means of continuous intravenous infusion up to concentrations of 20 micrograms/ml serum, giving a gradual decrease in cytochrome c oxidase activity. This activity was used as a marker for functionally capable mitochondria and as a tool to monitor the efficiency of inhibition of mitochondrial protein synthesis. It is shown that liver regeneration is strongly impaired after a period of pretreatment of 22 days or more and continuation of oxytetracycline treatment during regeneration. The mitochondrial respiratory capacity is reduced to 14% of the control value under these conditions. To obtain inhibitory levels within the regenerating liver, it was necessary to raise the serum levels slightly above 20 micrograms/ml. This measure is most likely required because of the poor vascularization of the regenerating liver. The serum levels were kept, however, far below those known to inhibit cytoplasmic protein synthesis. The results show that in normal liver the respiratory capacity must be reduced drastically before energy-requiring processes become affected. In Zajdela hepatoma cells, similar effects are found after reduction of the cytochrome c oxidase activity to 38%. This difference in sensitivity is probably based on the different mitochondrial content of liver cells and the liver-derived Zajdela cells.

ATP Synthetase Complexes↗
PubMed1986

Regulation of lipid peroxidation by ATP synthetase substrates in rat liver mitochondria.

The addition of cumene hydroperoxide to succinate-energized mitochondria has been shown to result only in an insignificant acceleration of lipid peroxidation. Phosphate accelerates this process, while ADP reverses the phosphate effect. The phosphate and ADP effects are revealed in the mitochondrial matrix. N-Ethylmaleimide, the phosphate transport inhibitor, taken at low concentrations, prevents the phosphate effects; accordingly, carboxyatractyloside, the nucleotide transport inhibitor, prevents the ADP effects. The addition of an uncoupler to the energized mitochondria has no effect on the induction of lipid peroxidation by cumene hydroperoxide in the presence of phosphate and does not reverse the ADP effect.

ATP Synthetase Complexes↗
PubMed1984

The DCCD-reactive aspartyl-residue of subunit C from the Escherichia coli ATP-synthase is important for the conformation of F0.

The effect of various point mutations in subunits a and and c of the E. coli ATP-synthase was characterized. In each of the mutants there was no F0-dependent H+-conduction, but still an ATPase-activity comparable to wildtype activities. In addition, the subunit b could be extracted from the mutant's F0 but not from the F0 of wildtype. The effects are interpreted as a change in the conformation of F0 caused by the different mutations.

ATP Synthetase Complexes↗
PubMed1986

A quantitative evaluation of the extent of inner mitochondrial membrane destruction after freezing-thawing based on functional studies.

An assay based on comparative investigation of ATPase and ATP synthetase changes in the activity in rat liver mitochondria after low temperature and uncoupler 2,4-dinitrophenol treatment is considered. By varying the activity of the respiratory chain, three extents of membrane cryoinjury could be distinguished by monitoring the changes in ATPase activity under different types of cryoinfluence. The first extent corresponds to a minimum membrane destruction, where the action of the respiratory chain compensates the changes in proton permeability and the cryotreatment does not change the ATPase activity. The second extent corresponds to changes in ion permeability which is partially compensated by the respiratory chain action. The third extent corresponds to a maximum membrane destruction and, therefore, maximum increase in permeability which is related to the irreversible stimulation of the ATPase activity and complete inhibition of the phosphorylation. In this study the extent of cryoinjury in mitochondrial preparations frozen and thawed at different rates was evaluated using this method.

2,4-Dinitrophenol↗
PubMed1983

The role of lipid peroxidation in the induction of cation transport in rat liver mitochondria. The antioxidant effect of oligomycin and dicyclohexylcarbodiimide.

Lipid peroxidation in mitochondria induced by Fe2+ in the presence of ascorbate or by cumene hydroperoxide in the presence of phosphate results in a drop of the membrane potential and in K+ efflux. The inhibitors of ATP-synthetase (oligomycin and dicyclohexylcarbodiimide (DCCD)) are capable of preventing lipid peroxidation, stabilizing the membrane potential and inhibiting potassium efflux. The same effects are observed in the presence of ionol or alpha-tocopherol. In contrast to antioxidant protection the effects of oligomycin and DCCD are reversed by the uncoupler (FCCP). The functional link between non-enzymatic lipid peroxidation, proton conduction through Fo component of ATP-synthetase and induced cation transport is suggested.

ATP Synthetase Complexes↗
PubMed1984

Relationships of respiratory chain and ATP-synthetase in energized mitochondria.

The present study reveals that the previously described effect of ATP-synthetase inhibition concomitant with inhibition of respiratory chain functioning may be observed at different absolute values of delta psi on the mitochondrial membrane. This fact points out that the membrane potential is not a unique regulator in coupling of ATP-synthetase and respiratory chain activities. We found, using the double-inhibitor titration technique, that ATP-synthetase inhibition induces proportional inhibition of respiratory chain enzymes and vice versa respiratory chain inhibition induces proportional inhibition of ATP-synthetase. This effect is shown to exist only when osmolarity is close to 150-300 (mosM) (in the physiological range). The coupling effectivity (ADP/O) of mitochondria under these conditions is maximal. Under conditions of high osmolarity (400-600 mosM) the respiratory chain and ATP-synthetase behave as if they were coupled by bulk phase delta -mu H+, from the kinetic point of view.

ATP Synthetase Complexes↗
PubMed1992

p56lyn catalyzes a reversible autophosphorylation reaction and a nucleoside diphosphate kinase reaction.

The reversible autophosphorylation of the pp60c-src family tyrosine kinase, p56lyn has been characterized by a simple procedure that involves the examination of the enzyme catalyzed radioisotope exchange between ATP and ADP. The equilibrium constant of the reaction was determined to be 3.31 and corresponded to a standard free energy of hydrolysis of the phosphotyrosine bond in p56lyn of -8.08 kcal/mol. GDP was capable of substituting for ADP as phosphate acceptor so that p56lyn displayed a nucleoside diphosphate kinase activity.

ATP Synthetase Complexes↗