Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Submitochondrial Particles”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 703 records · Page 39Linked to original sources
PubMed1988

Effects of antibodies to intact cytochrome-c oxidase and its subunit V on the enzymatic activity.

Antibodies have been raised in rabbits against whole beef heart cytochrome-c oxidase and purified subunit V. Antioxidase recognizes nearly all the enzyme subunits but reacts very strongly with subunits II and IV. Antisubunit V is quite specific against subunit V. Inhibition of enzyme activity by antioxidase is typically biphasic in time, indicating populations of both rapidly and slowly reacting molecules. Variation of cytochrome c concentration shows partially competitive kinetics, but the antibody also affects "internal" enzymatic events, including the catalytic turnover induced by N,N,N',N'-tetramethyl-p-phenylenediamine alone and the spin-state change in cytochrome a3 that follows reduction of cytochrome a. No spectral effects can be seen however. Antioxidase also inhibits proteoliposomal respiration with external cytochrome c, but not that with internally trapped cytochrome c. No functionally significant epitopes are detectable on the N side of the membrane in proteoliposomes, although some small effects can be seen with submitochondrial particles. Antisubunit V inhibits the isolated enzyme by at least 60%. The inhibition at high ionic strength induces a biphasic pattern with respect to cytochrome c concentration. Antisubunit V may thus slow the dissociation of cytochrome c from its complex with the enzyme. Antisubunit V has only small effects on the activities of proteoliposomal and submitochondrial particle oxidase in either orientation. On subunit V, some sites, the binding of which can give rise to inhibition, are thus not accessible to antisubunit V when the enzyme is embedded in a functional membrane system.

Animals↗
PubMed1993

Effects of equisetin on rat liver mitochondria: evidence for inhibition of substrate anion carriers of the inner membrane.

The effect of equisetin, an antibiotic produced by Fusarium equiseti, has been studied on mitochondrial functions (respiration, ATPase, ion transport). Equisetin inhibits the DNP-stimulated ATPase activity of rat liver mitochondria and mitoplasts in a concentration-dependent manner; 50% inhibition is caused by about 8 nmol equisetin/mg protein. The antibiotic is without effect either on the ATPase activity of submitochondrial particles or on the purified F1-ATPase. It inhibits both the ADP- or DNP-activated oxygen uptake by mitochondria in the presence of glutamate+malate or succinate as substrates, but only the ADP-stimulated respiration is inhibited if the electron donors are TMPD+ascorbate. It does not affect the NADH or succinate oxidation of submitochondrial particles. Equisetin inhibits in a concentration-dependent manner the active Ca(2+)-uptake of mitochondria energized both by ATP or succinate without affecting the Ca(2+)-uniporter itself. The antibiotic inhibits the ATP-uptake by mitochondria (50% inhibition at about 8 nmol equisetin/mg protein) and the Pi and dicarboxylate carrier. It does not lower the membrane potential at least up to 200 nmol/mg protein concentration. The data presented in this paper indicate that equisetin specifically inhibits the substrate anion carriers of the mitochondrial inner membrane.

Adenosine Diphosphate↗
PubMed1977

Mitochondrial sulfhydryl groups. A possible endogenous probe of conformational changes in the mitochondrial membrane.

The protein-bound sulfhydryl (SH) groups of the mitochondrial membrane were determined with Ellman's reagent in energized and non-energized configurational states of mitochondria and submitochondrial particles. When beef heart mitochondria were energized by respiration, there was a decrease in titratable protein-bound SH groups which varied according to substrate: NADH-linked substrates induced a decrease of about 10 nmol per mg of protein,succinate about 7, and ascorbate-tetramethyl-p-phenylene-diamine about 3. Similar changes occurred in phosphorylating submitochondrial particles. A decrease in SH titer was also observed in non-energized conditions, induced by hypotonic treatment and by some reagents inhibiting electron transport and oxidative phosphorylation and inducing orthodox configuration. These changes in protein-bound SH groups might be useful in analyzing the conformational states of mitochondrial membranes.

Animals↗
PubMed2003

Inhibition of mouse liver respiration by Chelidonium majus isoquinoline alkaloids.

The alkaloids from Chelidonium majus L. which had a significant inhibitory effect in mitochondrial respiration were those which contain a positive charge due to a quaternary nitrogen atom, i.e., chelerythrine, sanguinarine, berberine and coptisine, both with malate+glutamate or with succinate as substrates. When malate+glutamate was used as substrate, chelerythrine and berberine, which contain methoxy groups, were particularly more active, since they had a strong effect even at low concentrations. In submitochondrial particles, berberine and coptisine had a marked inhibitory effect on NADH dehydrogenase activity but practically no effect on succinate dehydrogenase activity, whereas chelerythrine and sanguinarine inhibited more strongly succinate dehydrogenase than NADH dehydrogenase, which is in agreement with the results found for mitochondrial respiration. Protopine and allocryptopine, which did not inhibit mitochondrial respiration, strongly inhibited NADH dehydrogenase in submitochondrial particles, but had no effect on succinate dehydrogenase activity.

Alkaloids↗
PubMed1998

Binding of the fluorescein derivative eosin Y to the mitochondrial ADP/ATP carrier: characterization of the adenine nucleotide binding site.

As the SH-reactive fluorescein derivative eosin-5-maleimide (EMA) specifically labels Cys159 in the second loop facing the matrix space (loop M2) of the ADP/ATP carrier in bovine heart submitochondrial particles [Majima, E., Koike, H., Hong, Y.-M., Shinohara, Y., and Terada, H. (1993) J. Biol. Chem. 268, 22181-22187], we studied the interaction of non-SH-reactive eosin Y, an analog of EMA, with the carrier under various conditions to characterize its binding. Eosin Y was found to inhibit ADP transport by binding to loop M2 in submitochondrial particles, but not in mitochondria. Its Ki for transport (0.33 microM) was found to be very similar to its Kd (0.53 microM) for specific binding to the carrier. Bound eosin Y was displaced by the transport substrates ADP and ATP, but not by untransportable GTP, suggesting that eosin Y bound to the specific binding site of ADP and ATP. The three-dimensional structure and electrostatic features of eosin Y were very similar to those of ADP, and the hydrophobic property and divalent charge of eosin Y were very important for its binding to the carrier. Based on these results, the features of the binding site of the transport substrates are considered.

Adenine Nucleotides↗
PubMed1985

Changes in activity and F1 content of mitochondrial H+-ATPase in regenerating rat liver.

Submitochondrial particles prepared from rat liver during hepatic regeneration exhibit a depressed ATPase activity which is correlated with a decrease in F1 subunit content as shown by SDS-PAGE. Use of an antibody directed against the F1 portion of the H+-ATPase complex demonstrated that there is a definite decrease in the amount of beta-subunit of F1 in both submitochondrial particles and mitochondria from rat liver 24 h after partial hepatectomy.

Animals↗
PubMed2003

The mitochondrial and prokaryotic proton-translocating NADH:ubiquinone oxidoreductases: similarities and dissimilarities of the quinone-junction sites.

The catalytic properties of the rotenone-sensitive NADH:ubiquinone reductase (Complex I) in bovine heart submitochondrial particles and in inside-out vesicles derived from Paracoccus denitrificans and Rhodobacter capsulatus were compared. The prokaryotic enzymes catalyze the NADH oxidase and NADH:quinone reductase reactions with similar kinetic parameters as those for the mammalian Complex I, except for lower apparent affinities for the substrates--nucleotides. Unidirectional competitive inhibition of NADH oxidation by ADP-ribose, previously discovered for submitochondrial particles, was also evident for tightly coupled P. denitrificans vesicles, thus suggesting that a second, NAD(+)-specific site is present in the simpler prokaryotic enzyme. The inhibitor sensitivity of the forward and reverse electron transfer reactions was compared. In P. denitrificans and Bos taurus vesicles different sensitivities to rotenone and Triton X-100 for the forward and reverse electron transfer reactions were found. In bovine heart preparations, both reactions showed the same sensitivity to piericidin, and the inhibition was titrated as a straight line. In P. denitrificans, the forward and reverse reactions show different sensitivity to piericidin and the titrations of both activities were curvilinear with apparent I(50) (expressed as mole of inhibitor per mole of enzyme) independent of the enzyme concentration. This behavior is explained by a model involving two different sites rapidly interacting with piericidin within the hydrophobic phase.

Animals↗
PubMed1993

pH dependent conformational changes modulate functional activity of the mitochondrial ATPase inhibitor protein.

A 12kDa, heat stable protein (IF1) inhibiting hydrolytic activity of submitochondrial particles was purified to electrophoretic homogeneity from buffalo heart mitochondria. Specific activity of the purified fraction was > 5000 units/mg. Maximal inhibition was observed at pH 6.0 and was Mg++ and ATP dependent. Circular dichroism studies showed that the inhibitor peptide undergoes a dramatic, reversible conformational change in response to pH which correlates well with its ability to inhibit ATP hydrolysis catalyzed by inhibitor depleted submitochondrial particles. It is shown for the first time that IF1 with a predominantly beta-sheet component is more efficient at suppressing ATPase activity.

Animals↗
PubMed2007

Roles of bound quinone in the single subunit NADH-quinone oxidoreductase (Ndi1) from Saccharomyces cerevisiae.

To understand the biochemical basis for the function of the rotenone-insensitive internal NADH-quinone (Q) oxidoreductase (Ndi1), we have overexpressed mature Ndi1 in Escherichia coli membranes. The Ndi1 purified from the membranes contained one FAD and showed enzymatic activities comparable with the original Ndi1 isolated from Saccharomyces cerevisiae. When extracted with Triton X-100, the isolated Ndi1 did not contain Q. The Q-bound form was easily reconstituted by incubation of the Q-free Ndi1 enzyme with ubiquinone-6. We compared the properties of Q-bound Ndi1 enzyme with those of Q-free Ndi1 enzyme, with higher activity found in the Q-bound enzyme. Although both are inhibited by low concentrations of AC0-11 (IC(50) = 0.2 microm), the inhibitory mode of AC0-11 on Q-bound Ndi1 was distinct from that of Q-free Ndi1. The bound Q was slowly released from Ndi1 by treatment with NADH or dithionite under anaerobic conditions. This release of Q was prevented when Ndi1 was kept in the reduced state by NADH. When Ndi1 was incorporated into bovine heart submitochondrial particles, the Q-bound form, but not the Q-free form, established the NADH-linked respiratory activity, which was insensitive to piericidin A but inhibited by KCN. Furthermore, Ndi1 produces H(2)O(2) as isolated regardless of the presence of bound Q, and this H(2)O(2) was eliminated when the Q-bound Ndi1, but not the Q-free Ndi1, was incorporated into submitochondrial particles. The data suggest that Ndi1 bears at least two distinct Q sites: one for bound Q and the other for catalytic Q.

Animals↗
PubMed1981

Properties of binding sites for adenine nucleotides on ATPase from yeast mitochondria.

High pressure column chromatography was applied to estimate the bound nucleotides on F1-ATPase. In this way, various species of adenine nucleotide in 0.1 to 0.3 mg of enzyme protein were well separated and estimated with a precision of about 10 nmol within 10 min. ATPase in submitochondrial particles contained 2 mol of ATP and 1 to 2 mol of ADP. The nucleotide content and binding nature of the enzyme varied at different stages of purification, but a total of four binding sites were found in enzyme preparations at all steps. Highly purified enzyme had two tight binding sites for ATP and two loose binding sites, one for ATP and one for ADP. The tight binding of ADP observed in submitochondrial particles was reconstituted by continuous supply of ATP and Mg2+ to the purified enzyme. Removal and rebinding of the nucleotides did not affect ATP-hydrolyzing activity but caused conformational changes of the enzyme, as demonstrated by measuring cold-lability and trypsin digestion. An analog of ATP, AMPP(NH)P, was found to bind to loose binding sites of the purified enzyme with 2 mol of tightly bound ATP, and to inhibit ATP-hydrolyzing activity competitively. The analog also bound to the tight sites under special conditions, protecting the enzyme against cold inactivation. During enzymatic hydrolysis of [3H]ATP, labeled ATP and ADP were both bound at the loose sites, but only slight amounts of these nucleotides were bound to the tight sites. From these results it is inferred that the loose sites are catalytic, while the tight sites are not.

Adenine Nucleotides↗
PubMed1975

The rapid labeling of adenosine triphosphate by 32P-labeled inorganic phosphate and the exchange of phosphate oxygens as related to conformational coupling in oxidative phosphorylation.

Evidence is presented that extends and amplifies the concept that in oxidative phosphorylation energy input serves to bring about release of ATP formed at a catalytic site by reversal of hydrolysis. The evidence with beef heart submitochondrial particles includes additional demonstration of uncoupler insensitive Pi leads to HOH exhchange, demonstration that this exchange is sensitive to the specific phosphorylation inhibitor, oligomycin, and demonstration that the small burst of uncoupler-insensitive ATP, rapidly labeled after addition of a tracer of 32Pi, behaves in a manner consistent with its participation as a membrane-bound intermediate in the Pi leads to HOH exchange. In addition, data are presented showing that addition of hexokinase plus glucose to submitochondrial particles in presence of ADP and Pi considerably lowers the Pi leads to HOH exchange but that further addition of cyanide or 2,4-dinitrophenol or both has little additional effect. Such data are compatible with no energy requirement for formation of bound ATP. However, with a large excess of hexokinase, the rate of the Pi leads to HOH exchange is further depressed. This could reflect some use of energy to promote formation of ATP at the catalytic site or to maintain the integrity of the phosphorylation system. Relationships of these findings to related information in the field are discussed.

Adenosine Triphosphate↗
PubMed1987

Protonic inhibition of the mitochondrial adenosine 5'-triphosphatase in ischemic cardiac muscle. Reversible binding of the ATPase inhibitor protein to the mitochondrial ATPase during ischemia.

Twenty minutes of ischemia in canine cardiac muscle produced a 50% to 60% inhibition of the mitochondrial ATPase. The inhibition has been shown to be triggered by a drop in cell pH under the non-energizing conditions which prevail in ischemic cells (Rouslin, W J Biol Chem 258, 9657-9661 (1983). In the present study we showed that the ATPase inhibition produced in situ in ischemic cardiac muscle was preserved in submitochondrial particles (SMP) prepared from mitochondria isolated from the ischemic tissue. The ischemic SMP ATPase was 45 +/- 3% as active as that of control particles. Measurements of the amounts of ATPase inhibitor protein of Pullman and Monroy present in extracts of control and ischemic SMP by two independent methods, titration of rat heart SMP ATPase and radioimmunoassay, revealed that control SMP contained 62 +/- 4% as much inhibitor as ischemic SMP as estimated by the titration procedure and 66 +/- 3% as much as estimated by the RIA. The results suggest that about one-third of the inhibitor was displaced from the control SMP. Finally, submitochondrial particles prepared from 20 min ischemic heart muscle showed a 2.5-fold increase in ATPase specific activity and a concomitant release of 35% of their inhibitor as a result of subsequent reenergization in vitro. Carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) prevented both ATPase reactivation and inhibitor release. These findings support the hypothesis that the observed in situ ATPase inhibition is inhibitor protein mediated. Moreover, they suggest a pathophysiological function for the inhibitor protein in cardiac muscle.

Adenosine Triphosphatases↗
PubMed2005

Inhibition of the mitochondrial ATP synthesis by polygodial, a naturally occurring dialdehyde unsaturated sesquiterpene.

Polygodial is a naturally occurring sesquiterpene dialdehyde that exhibits several pharmacologically interesting activities. Among them, its antifungal properties have been more thoroughly studied. The mitochondrial ATPase has been suggested as one of the possible targets for polygodial action. However, its mechanism of action is not well defined yet. The effect of polygodial on the mitochondrial energy metabolism is described in this paper. Polygodial inhibited ATP synthesis coupled to succinate oxidation in beef-heart submitochondrial particles at concentrations (IC(50)=2.4+/-0.1 microM) which marginally affected electron transport and ATPase activity (IC(50)=97+/-4 microM). A transitory stimulation of the electron transport in intact rat liver mitochondria in state 4 was also obtained at low polygodial concentrations (EC(50)=20+/-4 microM). These results suggest that polygodial uncouples ATP synthesis from electron transport at low concentrations. Similar concentrations of polygodial partially abolished the ANS fluorescence enhancement (IC(50)=2.2+/-0.4 microM) induced by succinate oxidation in submitochondrial particles but did not collapse the DeltapH. We postulate that polygodial uncouples mitochondrial ATP synthesis by affecting the electrical properties of the membrane surface and consequently collapsing the membrane potential (Deltapsi) and/or the localized transmembrane pH difference (DeltapH(S)) without affecting the DeltapH between the two bulk aqueous phases (DeltapH(B)). The relevance of these findings for the understanding of the biochemical basis of the antifungal activity of polygodial and the evaluation of its potentiality as a therapeutic agent are discussed.

Adenosine Triphosphate↗
PubMed1996

Oxygenation of biomembranes by mammalian lipoxygenases: the role of ubiquinone.

15-Lipoxygenase is implicated in the selective breakdown of mitochondria during red cell maturation by virtue of its capability of directly oxygenating phospholipids. To address the reason of the selectivity for mitochondria, we studied the reaction of pure rabbit 15-lipoxygenase with beef heart submitochondrial particles in vitro. This reaction is characterised by a loss of polyenoic fatty acids, the formation of phospholipid-bound hydroperoxy- and keto-polyenoic fatty acids, and oxidative modification of membrane proteins. The total oxygen uptake exceeds the formation of oxygenated polyenoic fatty acids several times. The excessive oxygen uptake was not inhibited by 3,5-di-tert-butyl-4-hydroxytoluene or by respiratory inhibitors, but was partly suppressed by superoxide dismutase plus catalase, salicylate, or mannitol. Pentane-extraction of the submitochondrial particles abolished the excessive oxygen uptake, whereas reconstitution with ubiquinone- 50 restored it. A marked excessive oxygen uptake did not occur during the analogous reaction with erythrocyte ghosts. It is proposed that ubiquinone-50 triggers the formation of hydroxyl radicals from 15-lipoxygenase-derived hydroperoxy-lipids via a Fenton-type reaction driven by ubisemiquinone radicals. A new prooxidative function of ubiquinone in the biologically programmed degradation of mitochondria in certain types of cells is proposed.

Amino Acids↗
PubMed1981

A study of the dicyclohexylcarbodiimide-binding component of the mitochondrial ATPase complex from beef heart.

1. The binding of [14C]-dicyclohexylcarbodiimide to membrane proteins of beef heart mitochondria has been investigated using dodecylsulphate/polyacrylamide gel electrophoresis. Upon incubation of submitochondrial particles with low concentrations of dicyclohexylcarbodiimide (5 nmol/mg protein) radioactivity was incorporated into three components with apparent molecular weights of 30000, 18000 and less than 6500. Only the two smaller components were found to be extracted into chloroform/methanol. The same two components were labelled when the isolated ATPase complex or a reconstituted F0F1 system was incubated with low concentrations of dicyclohexylcarbodiimide. High concentrations of dicyclohexylcarbodiimide (20-100 nmol/mg protein) resulted in binding to several mitochondrial proteins. 2. The maximal amount of dicyclohexylcarbodiimide which can bind to submitochondrial particles, the isolated ATPase complex, and the reconstituted F0F1 system was found to exceed the amount required for maximal inhibition of the ATPase activity by several-fold. The distribution of the bound [14C]dicyclohexylcarbodiimide between the different dicyclohexylcarbodiimide-binding components was investigated as a function of dicyclohexylcarbodiimide concentration. The smallest and largest components revealed a high affinity for dicyclohexylcarbodiimide-binding which paralleled the inhibition of ATPase activity. The intermediate component had a markedly lower affinity for dicyclohexylcarbodiimide-binding. 3. The larger dicyclohexylcarbodiimide-binding component of the isolated ATPase complex can be converted into the smaller component by treatment of the ATPase complex with performic acid. Partial conversion can also be achieved by extraction of the band from the dodecylsulphate-polyacrylamide gel after electrophoresis, followed by re-electrophoresis. The observations suggest that the larger component may be an oligomer of the smaller one. 4. Using concentrations of oligomycin and dicyclohexylcarbodiimide which were equal to or greater than those required for maximal inhibition of the ATPase activity, oligomycin was found to diminish the binding of [14C]dicyclohexylcarbodiimide to both dicyclohexylcarbodiimide-binding components of the isolated ATPase complex.

Adenosine Triphosphatases↗
PubMed1984

The interaction of adriamycin with cardiolipin in model and rat liver mitochondrial membranes.

The interaction of adriamycin with cardiolipin in model membranes and in various membrane preparations derived from rat liver mitochondria was studied and the results are analyzed in the light of a possible specific interaction between adriamycin and cardiolipin. It was found that adriamycin binds to cardiolipin-containing model membranes with a fixed stoichiometry of two drug molecules per cardiolipin. Furthermore, the extent of drug complexation by mitochondria and mitoplasts (inner membrane plus matrix) is in reasonable agreement with their cardiolipin content. In contrast, adriamycin-binding curves of inner membrane ghosts and submitochondrial particles reveal considerable association to an additional site, presumably RNA. The evidence for the potential importance of RNA as a target comes from experiments on outer membranes and microsomes which both appear to bind substantial amounts of adriamycin. Removal of the major part of the RNA associated with these fractions by EDTA treatment is accompanied by a dramatic reduction of binding capacity. We propose that endogenous RNA present in mitochondria and mitoplasts is not accessible for adriamycin at low concentrations of the drug due to the presence of an intact lipid barrier. This potential site comes to expression in ghosts and submitochondrial particles, due to the absence of an intact lipid bilayer and due to the inside-out orientation of the limiting membrane, respectively. Electron microscopical studies show that adriamycin induces dramatic changes in mitochondrial morphology, similar to the uncoupler-induced effects described by Knoll and Brdiczka (Biochim. Biophys. Acta 733, 102-110 (1983). Adriamycin has an uncoupling effect on mitochondrial respiration and oxidative phosphorylation. The concentration dependence of this effect correlates with the adriamycin-binding curve for mitochondria which implies that only bound adriamycin actively inhibits respiration.

Animals↗
PubMed1981

Molecular alterations in the respiratory chain of rat liver after chronic ethanol consumption.

Mitochondria, submitochondrial particles, and hepatocytes prepared from the livers of rats treated chronically with ethanol (36% calories, 40 days) exhibited significant alterations in the content of specific respiratory chain components. As measured by heme absorbance, the amounts of substrate-reducible cytochromes aa3 and b were each decreased about 50%, while the amount of cytochromes c plus c1 was unchanged after chronic ethanol treatment. The amounts of extractable flavin and ubiquinone associated with the respiratory chain were also unaltered. The effects of an altered cytochrome ratio on electron transport were studied by measurements of the aerobic reduction levels of the cytochromes during steady state respiration using submitochondrial particles. The aerobic reduction patterns observed after chronic ethanol treatment reflected the differential alterations in amounts of respiratory chain components present in the membranes, as well as the intrinsic kinetic characteristics of respiratory. The most notable change was observed during ascorbate oxidation, in which case cytochrome c was maintained at a higher level of steady state reduction. The results suggest that at the level of the electron transport chain itself, the lower respiratory rates found after chronic ethanol treatment arise, at least in part, from specific alterations in the content of particular electron transfer chain carriers, but that different alterations limit the rate of respiration with different substrates.

Animals↗
PubMed1989

Effect of reducing agents and uncouplers on the electrical potential generated by mitochondrial ATPase activity.

Beef heart submitochondrial particles bound to phospholipids impregnated filters generated an electrical potential upon the addition of ATP. The magnitude of the electrical potential reached depended on the phospholipid mixture composition used for filter impregnation, phosphatidylethanolamine being the active component for the electrical potential generation. Uncoupler FCCP (p-trifluoromethoxy carbonyl cyanide phenylhydrazone) inhibited the transmembrane electrical potential generation by diminishing the electrical resistance of the system as a result of its protonophoric action. However, uncouplers 2, 4-dinitrophenol and dicoumarol did not provoke large modifications of the electrical resistance under the conditions of pH and concentration used, and their action varied with the time elapsed after the submitochondrial particles purification, favouring the idea of the uncoupler interaction with a specific site on the membrane. Addition of sodium dithionite resulted in a higher plateau value for the electrical potential consistent with the promoted increase in ATPase activity. The effect of this agent was reversed by the 2,6-dichlorophenol-indophenol added at equivalent concentrations.

Animals↗