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At least 19 recordsLinked to original sources
PubMed1976

The use of several energy-coupling reactions in characterizing mutants of Escherichia coli K12 defective in oxidative phosphorylation.

Oxidative phosphorylation, ATP-32Pi exchange, ATP-dependent quenching of acridine-dye fluorescence, ATP-dependent transhydrogenase and ATP-dependent transport of thiomethyl beta-D-galactoside are shown to be experimentally equivalent tools to study the functional state of the ATPase complex in Escherichia coli wild-type and mutant strains defective in oxidative phosphorylation. According to these criteria ten mutants in the ATPase complex were classified having lesions in the unc A,B region of the chromosome. The first mutant type lacks ATPase activity, but the membrane-integrated part of the complex remains functional (class I). The second mutant type lacks a functional membrane-integrated part, but retains ATPase activity (class II). The third mutant type is shown to be defective in both parts of the ATPase complex (class III).

Adenosine Triphosphatases↗
PubMed2025

Structural diversity and evolutionary constraints of oxidative phosphorylation.

The oxidative phosphorylation (OxPhos) system is central to metabolism. The more than 90 structural subunits are encoded by different chromosome categories (autosomal, X, and mtDNA). The system is envisioned as an invariant structure between cells and individuals. However, a comprehensive analysis of the 1,000 Genomes Project data reveals unexpected genetic intra-individual variability resulting from the heterozygosity of diploid autosomal genes, while diversity at the population level is generated by variability in mtDNA. We characterized the different levels of structural constriction at evolutionary and population levels for all OxPhos protein residues. To support this analysis, we developed ConScore, a conservation-based predictor of variant impact within OxPhos proteins (area under the receiver operating characteristic curve [ROC-AUC] = 0.97; area under the precision-recall curve [PR-AUC] = 0.94). Notably, for the nuclear-encoded subunits, we found mechanisms limiting individual variability as allelic imbalance or homozygosity bias. Integrating structural, functional, and genetic data, we highlight the significance of each OxPhos protein position, expanding insights into its role in speciation and disease.

Oxidative Phosphorylation↗
PubMedDate not supplied

[Oxidative phosphorylation in Propionibacterium].

Oxidative phosphorylation during electron transport in the respiratory chain was found in two propionic bacteria, P. shermanii and P. petersonii. Its effectiveness, with oxygen as the terminal acceptor of electrons, was higher in P. petersonii, a more aerobic culture, than in P. shermanii. Oxidative phosphorylation with the participation of the electron transport chain was not found in P. petersonii in the absence of oxygen. Oxidative phosphorylation can take place together with the reactions of propionic fermentation in P. shermanii upon a small rearrangement of the respiration chain (if fumarate reductase is substituted for cytochrome oxidase).

Aerobiosis↗
PubMed1979

Effect of uncouplers and inhibitors of oxidative phosphorylation on the reduced and oxidized forms of mitochondiral ATPase.

A series of uncouplers and inhibitors of oxidative phosphorylation have been studied with regard to their effect on the hydrolytic activity of the reduced and oxidized forms of isolated or membrane-bound mitochondrial ATPase. Uncouplers (2,4-dinitrophenol, dicoumarol), which are also activators of the hydrolytic activity of ATPase, were more potent activators on the oxidized form of the enzyme. Inhibitors of oxidative phosphorylation (oligomycin, azide and amytal) had a more potent inhibitory effect on the hydrolytic activity of ATPase in its reduced form. Purified F1-ATPase, oligomycin insensitive in the oxidized form of the enzyme, became sensitive to oligomycin in the reduced form. An interpretation of the results suggests the presence of a mechanism that unifies the action of these different compounds on the synthesis and hydrolysis of ATP catalyzed by mitochondrial ATPase.

Adenosine Triphosphatases↗
PubMed1977

Bépridil a new effector of oxidative phosphorylations.

Bépridil action on oxidative phosphorylations depends on the nature of the oxidized substrate. Thus it seemed to act as an uncoupler on the FAD-linked substrates as we have shown with succinate. But this property could not be applied to the NAD-linked substrates. Thus, in the presence of Bépridil, ADP would have opposite effects on the electron flow across the first site of oxidative phosphorylations; from one side the direct electron flow was decreased while from the other side, the reverse one was increased. Confirming this difference in its action, Bépridil did not affect the oxidative phosphorylation property of the cytochrome oxidase as could be deduced from the invariability of TMPD + ascorbate oxidation whether Bépridil was added or not. Moreover the effect of Bépridil on the P/O ratio was a dramatic demonstration of its selectivity. As a matter of fact this ratio was increased to a value near 5 for the NAD-linked substrate while it was decreased to near 0.4 with the FAD-linked substrate.

Amines↗
PubMedDate not supplied

[Lipids as possible proton carriers from the respiratory chain to ATP-synthetase and the mechanism of oxidative phosphorylation].

A scheme of oxidative phosphorylation is suggested according to which at the first stage due to the functioning of the electron-transport chain (ETC) in the points of coupling during relaxation of protein non-equilibrium conformation thermodynamically unfavourable transfer of H+ from H2O into the membrane takes place. Athe 2nd stage H+memb is carried by lipids from ETC-protein to ATP-synthetase. At the 3rd stage ATPase with ATP already contained in the active center seizes 2H+. In the course of subsequent protein relaxation the ATP interaction with the active center is disturbed, and ATP with protons transfers to H2O. In terms of the scheme proposed it proves possible to explain the respiratory control and formation of transmembrane potential difference, as well as the action mechanism of uncouplers and inhibitors of oxidative phosphorylation.

Adenosine Diphosphate↗
PubMed1992

Interaction of mitochondrially bound rat brain hexokinase with intramitochondrial compartments of ATP generated by oxidative phosphorylation and creatine kinase.

Previous work led to the conclusion that, during oxidative phosphorylation, mitochondrially bound hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) from rat brain was dependent on intramitochondrially compartmented ATP as substrate. The present study demonstrated that, when oxidative phosphorylation was functioning concurrently, mitochondrial creatine kinase could also generate intramitochondrial ATP serving as substrate for hexokinase. In the absence of concurrent oxidative phosphorylation, the kinetics of glucose phosphorylation with ATP generated by creatine kinase were not consistent with the supply of ATP from a saturable intramitochondrial compartment as formed during oxidative phosphorylation. Evidence for intramitochondrially compartmented ATP, generated by creatine kinase, was obtained; this was distinct from compartmented ATP generated by oxidative phosphorylation in terms of kinetics of generation of the compartment and its capacity, sensitivity to release by carboxyatractyloside, and sensitivity to disruption by digitonin. That oxidative phosphorylation did induce a dependence on intramitochondrial ATP as a substrate was further indicated by the observation that, although the initial rate of glucose phosphorylation by mitochondrial hexokinase depended on the extramitochondrial concentration of ATP present at the time oxidative phosphorylation was initiated, a final steady state rate of glucose phosphorylation was attained that was independent of extramitochondrial ATP levels. These and previous results emphasize the probable importance of nucleotide compartmentation in regulation of cerebral glycolytic and oxidative metabolism.

Adenosine Diphosphate↗
PubMed1992

[Oxidative phosphorylation of liver mitochondria in Oncomelania snail].

Oxidative phosphorylation of liver mitochondria in Oncomelania snail was separately detected by using oxygen electrode and spectrophotometer. ADP increased oxidative reaction of liver mitochondria from 0.187 to 0.318 mumol O2/mg protein.20 min. When certain substrates of citric acid cycle were added to liver mitochondria of Oncomelania snail, we found that oxidative phosphorylation increased to 0.353-0.444 mumol O2/mg protein.20 min. ATPase was detected in the liver of Oncomelania snail. The oxidative phosphorylation of mitochondria in Oncomelania snail could be markedly inhibited by DNP and molluscicide bromoacetamide, but the latter didn't show the inhibition of ATPase. (Figs. 1,2).

2,4-Dinitrophenol↗
PubMed1977

Effects of triiodothyronine on oxidative phosphorylation in immature rat brain mitochondria.

Oxidative phosphorylation was measured polarographically in brain mitochondria isolated from 1 to 3-week-old normal and triiodothyronine-treated rat pups. Adenosine diphosphate (ADP)/oxygen ratios with nicotinamide-adenine dinucleotide (NAD)-linked substrates, but not with succinate, were increased in brain mitochondria from experimental animals at each age. Control ratios and respiratory rates were not affected. Thus, the normal maturational increase in ADP/oxygen ratios with NAD-linked substrates is accelerated in brain mitochondria from rats treated with triiodothyronnie from birth. This effect on efficiency of oxidative phosphorylation is similar to that of throid hormones on other properties of the maturing brain.

Age Factors↗
PubMed1976

Oxidative phosphorylation in right-side-out membrane vesicles from Escherichia coli.

Oxidative phosphorylation in Escherichia coli membrane vesicles with a right-side-out orientation and loaded with ADP was investigated. Substrates of the electron transport chain could energize the phosphorylation of ADP, with the order of effectiveness being D-lactate greater than reduced phenazinemethosulfate greater than succinate greater than reduced nicotinamide adenine dinucleotide. Inhibitors of D-lactate oxidation, proton conductors, and inhibitor of the Mg2+ATPase (EC 3.6.1.3) all inhibited oxidative phosphorylation when coupled to D-lactate oxidation. ATP synthesis was absent in membrane vesicles prepared from a mutant strain lacking the Mg2+ATPase. Valinomycin or nigericin partially inhibited oxidative phosphorylation in the presence of potassium. Valinomycin plus nigericin completely inhibited ATP synthesis. The effect of various agents on the respiration-dependent establishment of a transmembrane pH gradient was also examined. NaCN and carbonyl cyanide p-trifluoromethoxyphenylhydrazone inhibited the establishment of a pH gradient while dicyclohexylcarbodiimide had no effect. These results are in good agreement with a chemiosmotic model for oxidative phosphorylation.

Arsenates↗
PubMed1975

Oxidative phosphorylation in mitochondria isolated from stressed rat heart.

Oxidative phosphorylation was measured polarographically in mitochondria isolated from rat heart. With regard to ADP/O ratio and respiratory control index, no differences were found among mitochondria isolated from normal, acutely (increased pneumatic resistance of the heart-lung preparation) and chronicly (renal hypertension) stressed heart. However, the acute stressed heart induced by strangulating the outflow tract of the heart-lung preparation showed clear depression and tendency to depression, respectively, in the level of ADP/O ratio and respiratory control index in mitochondria. The results indicate that there is no change in the oxidative phosphorylating mechanism of the myocardial mitochondria of nonfailed heart despite acute or chronic pressure loadings; however, there is an uncoupling of oxidative phosphorylation in mitochondria of the failed heart after acute strangulation of the outflow tract.

Adenosine Diphosphate↗
PubMed1992

Interaction of butylated hydroxyanisole with mitochondrial oxidative phosphorylation.

The antioxidant, butylated hydroxyanisole (BHA), has a number of effects on mitochondrial oxidative phosphorylation. In this study we apply the novel approach developed by Brand (Brand MD, Biochim Biophys Acta 1018: 128-133, 1990) to investigate the site of action of BHA on oxidative phosphorylation in rat liver mitochondria. Using this approach we show that BHA increases the proton leak through the mitochondrial inner membrane and that it also inhibits the delta p (proton motive force across the mitochondrial inner membrane) generating system, but has no effect on the phosphorylation system. This demonstrates that compounds having pleiotypic effects on mitochondrial oxidative phosphorylation in vitro can be analysed and their many effects distinguished. This approach is of general use in analysing many other compounds of pharmacological interest which interact with mitochondria. The implications of these results for the mechanism of interaction of BHA with mitochondrial oxidative phosphorylation are discussed.

Adenosine Triphosphate↗
PubMedDate not supplied

[Changes in oxidative phosphorylation in mitochondria of rat liver after introduction of thiophosphamide].

Oxidative phosphorylation in the rat liver mitochondria was studied as affected thiophosphamide 1, 6 and 24 h 3, 7, 15 and 30 days after administration of the chemopreparation. Considerable changes were found in oxidative phosphorylation. The degree of disturbances is different depending on the period which passed after radiomemetics administration. During the first hours and days oxidative phosphorylation is inhibited more and more, reaching the maximum three days later. In subsequent periods of the studies a gradual restoration of this bioenergetic index is observed. When oxidizing alpha-ketoglutarate by mitochondria the inhibition of respiration and phosphorylation is more profound than in case with succinate oxidation.

Animals↗
PubMed1975

Experimental mitochondrial myopathy produced by in vivo uncoupling of oxidative phosphorylation.

Two uncouplers of mitochondrial oxidative phosphorylation [2,4-dinitrophenol (DNP) and carbonylcyanide-m-chlorophenylhydrazone (CCCH)] were infused intra-arterially into a branch of the lower abdominal aorta of anesthetized rats over a 60-180 min period. An acute, severe, hypermetabolic state with systemic lactic acidosis and stiffness of the lower extremeities developed. In the plantaris muscles, by histochemistry, numerous "ragged red" fibers were present after the infusion. The "ragged red" areas presumably represented an absolute increase in mitochondrial mass in affected muscle fibers. By electron microscopy, linear inclusions were present in the intracristal space of many mitochondria. Simultaneous infusion of DNP and chloramphenicol, an inhibitor of mitochondrial protein synthesis, prevented the formation of ragged red fibers but not the intracristal inclusions. Infusion of relatively large amounts of oleic acid produced histochemical and electron-microscopic changes similar to those caused by the uncouplers. A possible pathogenesis of these reversible mitochondrial changes was discussed and their potential relevance to morphologic abnormalities of skeletal muscle mitochondria in human diseases was reviewed.

Animals↗
PubMed1976

Biochemical studies of pigments from a pathogenic fungus Microsporum cookei. III. Comparison of the effects of xanthomegnin and O-methylxanthomegnin on the oxidative phosphorylation of rat liver mitochondria.

The effects of xanthomegnin and O-methylxanthomegnin on the oxidative phosphorylation of rat liver mitochondria were compared. The n-octanol/water partition coefficient of xanthomegnin was markedly enhanced by O-methylation, but O-methylation of xanthomegnin reduced the uncoupling effect on the respiratory system of mitochondria. Analogous results were obtained in the uncoupling action of 5-hydroxy-1, 4-naphthoquinone (juglone) and 5-methoxy-1, 4-naphthoquinone (O-methyljuglone) on the oxidative phosphorylation of rat liver mitochondria. These data indicate that the phenolic hydroxyl groups of xanthomegnin might contribute to its uncoupling action on the oxidative phosphorylation of mitochondria. Bovine serum albumin (BSA) improved the efficiency of oxidative phosphorylation of mitochondria which were uncoupled by xanthomegnin. Spectroscopic observations revealed that xanthomegnin interacted with BSA by means of hydrophobic and ionic forces but O-methylxanthomegnin showed only hydrophobic interaction. Analogous interactions between mitochondria and xanthomegnin or O-methylxanthomegnin were observed. These results indicate that the uncoupling action of xanthomegnin on the respiratory system in mitochondria might involve ionic interaction of xanthomegnin with cationic residues in the hydrophobic region of mitochondrial membrane proteins.

Animals↗
PubMedDate not supplied

Functional behaviour of isolated heart muscle mitochondria after in situ ischemia. Polarographic analysis of mitochondrial oxidative phosphorylation.

Heart muscle mitochondria with satisfactory functional parameters of oxidative phosphorylation and with morphologically intact structure were isolated from canine myocardium employing a modified KEA-medium (0.18 M KCl, 10 mM EDTA, 0.5% bovine serum albumin, pH 7.1) according to Sordahl and Schwartz (1). The functional behaviour of mitochondria was investigated after different durations of in situ ischemia (cardioplegia, 15 degrees C) and correlated with metabolic findings. During ischemia the following changes were seen: 1. Successive reduction of electron flow. 2. Relatively small impairment of phosphorylation efficiency. 3. Less damage of FAD- than NAD-catalyzed oxidative phosphorylation. 4. A marked increase of electron flow and thus recovery of phosphorylation rate even after longer ischemic periods by addition of cytochrome c. As important factors of accelerating mitochondrial impairment during ischemia the myocardial ATP decrease, the lactate and H+-activity increase are discussed.

Adenosine Triphosphate↗