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.

SourceResearch connectionFrom yearThrough year

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

At least 1,009 records · Page 56Linked to original sources

PubMed1984

The oligomycin sensitivity conferring protein (OSCP) of beef heart mitochondria: studies of its binding to F1 and its function.

The binding of "oligomycin sensitivity conferring protein" (OSCP) to soluble beef-heart mitochondrial ATPase (F1) has been investigated. OSCP forms a stable complex with F1, and the F1 X OSCP complex is capable of restoring oligomycin- and DCCD-sensitive ATPase activity to F1- and OSCP-depleted submitochondrial particles. The F1 X OSCP complex retains 50% of its ATPase activity upon cold exposure while free F1 is inactivated by 90% or more. Both free F1 and the F1 X OSCP complex release upon cold exposure a part--probably 1 out of 3--of their beta subunits; whether alpha subunits are also lost is uncertain. The cold-treated F1 X OSCP complex is still capable of restoring oligomycin- and DCCD-sensitive ATPase activity to F1- and OSCP-depleted particles. OSCP also protects F1 against modification of its alpha subunit by mild trypsin treatment. This finding together with the earlier demonstration that trypsin-modified F1 cannot bind OSCP indicates that OSCP binds to the alpha subunit of F1 and that F1 contains three binding sites for OSCP. The results are discussed in relation to the possible role of OSCP in the interaction of F1 with the membrane sector of the mitochondrial ATPase system.

Adenosine Triphosphatases↗

PubMed1986

On the role of K+ on succinic dehydrogenase activity.

The effect of potassium ions on succinic dehydrogenase activity of mitochondria was studied. The results showed that in these organelles K+ induces inhibition of the respiratory control; moreover, in submitochondrial particles potassium inhibits the rate of oxidation of succinate. The results showed also that K+ does not changes the Km for succinate but diminishes the Vmax. In addition, the data provide evidence that mitochondria oxidizing glutamate-malate in a sucrose medium show a higher activity of succinate dehydrogenase than mitochondria incubated in KCl.

Adenosine Triphosphate↗

PubMed1977

Photoaffinity labeling of uncoupler binding sites on mitochondrial membrane.

3H 2-azido-4-nitrophenol, a photoactive uncoupler, has been synthesized, and its uncoupling action on oxidative phosphorylation and its binding to the mitochondrial membrane have been studied. The uncoupler bound covalently to the mitochondrial membrane on photoirradiation was 3-4 times that bound reversibly in the absence of light. When irradiation was carried out in the presence of serum albumin, covalent binding was significantly depressed. The pattern of loss of ATP-Pi exchange activity with increasing amounts of the uncoupler suggests that serum albumin prevents the binding of the uncoupler to the functional sites as well. Polyacrylamide gel electrophoresis of photoaffinity labeled submitochondrial particles in the presence of sodium dodecyl sulfate revealed that a 9000 dalton peptide bound high levels of uncoupler. Other proteins in the molecular weight range of 20,000-40,000 and 55,000 were also labeled. Photolysis in the presence of serum albumin or ATP decreased the covalent binding of the uncoupler to all the proteins, but particularly to the 20,000 dalton component. Soluble ATPase and the mitochondrial proteolipid purified from labeled mitochondria showed the presence of label.

Adenosine Triphosphate↗

PubMed1988

Chemical modification of active sites in relation to the catalytic mechanism of F1.

Recent studies of chemically modified F1-ATPases have provided new information that requires a revision of our thinking on their catalytic mechanism. One of the beta subunits in F1-ATPase is distinguishable from the other two both structurally and functionally. The catalytic site and regulatory site of the same beta subunit are probably sufficiently close to each other, and the interaction between the various catalytic and regulatory sites are probably sufficiently strong to raise the uni-site rate of ATP hydrolysis by several orders of magnitude to that of promoted (multi-site) ATP hydrolysis. Although all three beta subunits in F1 possess weak uni-site ATPase activity, only one of them (beta') catalyzes promoted ATP hydrolysis. But all three beta subunits catalyze ATP synthesis driven by the proton flux. Internal rotation of the alpha 3beta 3 or beta 3 moiety relative to the remainder of the F0F1 complex did not occur during oxidative phosphorylation by reconstituted submitochondrial particles.

Binding Sites↗

PubMed1988

Role of energy in oxidative phosphorylation.

This article reviews the current status of information regarding the role of energy in the process of oxidative phosphorylation by mitochondria. The available data suggest that in submitochondrial particles (SMP) energy is utilized for the binding of ADP and Pi and for the release of ATP bound at the catalytic sites of F1-ATPase. The process of ATP synthesis on the surface of F1 from F1-bound ADP and Pi appears to be associated with negligible free energy change. The rate of energy production by the respiratory chain modulates the kinetics of ATP synthesis between a low Km (for ADP and Pi)-low Vmax mode and a high Km-high Vmax mode. The Km extremes for ADP are 2-3 microM and 120-150 microM, and Vmax for ATP synthesis at high rates of energy production by bovine-heart SMP is about 440 S-1 (mole F1)-1 at 30 degrees C, which corresponds to 11 mumol ATP (min.mg of protein)-1. The interaction of dicyclohexylcarbodiimide (DCCD) or oligomycin at the proteolipid (subunit c) of the membrane sector (F0) of the ATP synthase complex alters the mode of ATP binding at the catalytic sites of F1, probably to one of lower affinity. It has been suggested that protonic energy might be conveyed to the catalytic sites of F1 in an analogous manner, i.e., via conformation changes in the ATP synthase complex initiated by proton-induced alterations in the structure of the DCCD-binding proteolipid. Finally, the relationship between the steady-state membrane potential (delta psi) and the rates of electron transfer and ATP synthesis has been discussed. It has been shown, in agreement with the delocalized chemiosmotic mechanism, that under appropriate conditions delta psi is exquisitely sensitive to changes in the rates of energy production and consumption.

Binding Sites↗

PubMed1991

Inhibition of membrane-bound succinate dehydrogenase by disulfiram.

The effect of disulfiram on succinate oxidase and succinate dehydrogenase activities of beef heart submitochondrial particles was studied. Results show that disulfiram inhibits both functions. Succinate and malonate suppress the inhibitory action of disulfiram when succinate dehydrogenase is stabilized in an active conformation. Disulfiram is not able to inhibit the enzyme when succinate dehydrogenase is inactivated by oxaloacetate. The inhibitory effect of disulfiram is reverted by the addition of dithiothreitol. From these results, it is proposed that disulfiram inhibits the utilization of succinate by a direct modification of an -SH group located in the catalytically active site of succinate dehydrogenase.

Animals↗

PubMed1993

Subunit structures of purified beef mitochondrial cytochrome bc1 complex from liver and heart.

The existence of tissue-specific isozymes of cytochrome c oxidase has been widely documented. We have now studied if there are differences between subunits of mitochondrial bc1 complexes isolated from liver and heart. For this purpose, we have developed a method for the purification of an active ubiquinol-cytochrome c oxidoreductase from adult bovine liver that includes solubilization of submitochondrial particles with deoxycholate, ammonium acetate fractionation, resolubilization with dodecyl maltoside, and ion exchange chromatography. The electrophoretic pattern of the liver preparation showed the presence of 11 subunits, with apparent molecular weights identical to the ones reported for the heart complex. Western blot analysis and isoelectric focusing followed by two-dimensional gels of bc1 complexes from liver and heart were compared, and no qualitative differences were observed. In addition, the high-molecular-weight subunits of the purified complexes from both tissues, subunits I, II, V, and VI, were isolated by PAGE in the presence of Coomasie Blue and subjected to limited proteolysis and to chemical digestion with cyanogen bromide and BNPS-skatol, and the peptide patterns were compared. Finally, two of the small-molecular-weight subunits from the liver complex were isolated (subunits VII and X), partially analyzed by amino terminal sequencing, and found to be identical with the reported sequence of their heart counterparts. The data suggest that, in contrast to the case of cytochrome c oxidase, bc1 complexes from liver and heart do not exhibit tissue-specific differences.

Amino Acid Sequence↗

PubMed1989

Effect of cetyltrimethylammonium on ATP hydrolysis and proton translocation in the F0-F1 H+-ATP synthase of mitochondria.

The amphiphylic alkyl cation cetyltrimethylammonium inhibits the catalytic activity of soluble and membrane-bound F1 in a noncompetitive fashion. In sonic submitochondrial particles the Dixon plot showed a peculiar pattern with upward deviation at cetyltrimethylammonium concentration higher than 80 microM. In membrane-bound F1 the inhibition by cetyltrimethylammonium was potentiated by the F0 inhibitor ologomycin. Cetyltrimethylammonium also inhibited the oligomycin-sensitive proton conductivity in F1-containing particles but was without any effect in F1-depleted particles. Also this inhibitory effect was potentiated by oligomycin. These results indicate functional cooperative interactions between F0 and F1.

Adenosine Triphosphate↗

PubMed1983

Isolation of two ATPase inhibitor proteins from mitochondria of rat skeletal muscle.

An ATPase inhibitor protein was isolated from mitochondria of rat skeletal muscle by alkaline extraction and then was purified. It differed in definitive ways from the ATPase inhibitor protein isolated previously by Ca2+-stripping of submitochondrial particles of rat skeletal muscle. The two ATPase inhibitor proteins were shown to be present together in intact mitochondria.

Animals↗

PubMed1976

Functional role of soluble mitochondrial ATPase subunits.

A preparation of soluble mitochondrial ATPase (coupling factor F1) containing no gamma and delta minor subunits has been isolated. The minor-subunits-deficient F1 was found to be competent in ATP hydrolysis. However, it did not demonstrate a "coupling" effect in EDTA-submitochondrial particles. A portion of the ATPase activity of EDTA particles, stimulated by the minor-subunits-deficient F1, was insensitive to oligomycin. ATPase activity of Na+-particles was changed only slightly by this F1. It is suggested that gamma and delta subunits are necessary to form specific contacts between the F1 molecule and components of the mitochrondrial membrane.

Adenosine Triphosphatases↗

PubMed1984

Membrane potential and surface potential in mitochondria: uptake and binding of lipophilic cations.

The uptake and binding of the lipophilic cations ethidium+, tetraphenylphosphonium+ (TPP+), triphenylmethylphosphonium+ (TPMP+), and tetraphenylarsonium+ (TPA+) in rat liver mitochondria and submitochondrial particles were investigated. The effects of membrane potential, surface potentials and cation concentration on the uptake and binding were elucidated. The accumulation of these cations by mitochondria is described by an uptake and binding to the matrix face of the inner membrane in addition to the binding to the cytosolic face of the inner membrane. The apparent partition coefficients between the external medium and the cytosolic surface of the inner membrane (K'o) and the internal matrix volume and matrix face of the inner membrane (K'i) were determined and were utilized to estimate the membrane potential delta psi from the cation accumulation factor Rc according to the relation delta psi = RT/ZF ln [(RcVo - K'o)/(Vi + K'i)] where Vo and Vi are the volume of the external medium and the mitochondrial matrix, respectively, and Rc is the ratio of the cation content of the mitochondria and the medium. The values of delta psi estimated from this equation are in remarkably good agreement with those estimated from the distribution of 86Rb in the presence of valinomycin. The results are discussed in relation to studies in which the membrane potential in mitochondria and bacterial cells was estimated from the distribution of lipophilic cations.

Animals↗

PubMed1977

An analysis of the binding of fluorescence probes in mitochondrial systems.

Measurements of the binding of the fluorescent probes 8-anilinonaphthalene-1-sulfonate (ANS) and ethidium ions to whole and disruped mitochondria and submitochondrial particles suggest that the inner mitochondrial membrane is freely permeable to the two probes. Equations relating the binding of permeant probes to the electro-chemical balance across the membrane of vesicular systems are derived and these equations used to analyze Scatchard plots of the binding of the two probes to energized and nonenergized mitochondria and EDTA particles.

Anilino Naphthalenesulfonates↗

PubMed1979

Visualization of mitochondrial coupling factor F1(ATPase) by freeze-drying.

It is known that the negatively stained preparations of inner mitochondrial membrane display characteristic approximately 9 nm F1 (ATPase) knobs projecting from the matrix surface. Freeze-etch studies have reported the absence of such knobs from the "etched" surface of the inner mitochondrial membranes. We have demonstrated their presence on the surface of SMP (submitochondrial particles) prepared by freeze-drying for transmission electron microscopy. This identification has been substantiated by comparison with freeze-dried TU particles (trypsin-urea treated SMP) that are devoid of F1 (ATPase). It has been suggested that a layer of water molecules is strongly adsorbed to the surface of SMP and does not sublime during normal freeze-"etching."

Adenosine Triphosphatases↗

PubMed2004

Quinine inhibits mitochondrial ATP-regulated potassium channel from bovine heart.

The mitochondrial ATP-regulated potassium (mitoK(ATP) channel has been suggested as trigger and effector in myocardial ischemic preconditioning. However, molecular and pharmacological properties of the mitoK(ATP) channel remain unclear. In the present study, single-channel activity was measured after reconstitution of the inner mitochondrial membrane from bovine ventricular myocardium into bilayer lipid membrane. After incorporation, a potassium-selective current was recorded with mean conductance of 103 +/- 9 pS in symmetrical 150 mM KCl. Single-channel activity of this reconstituted protein showed properties of the mitoK(ATP) channel: it was blocked by 500 microM ATP/Mg, activated by the potassium-channel opener diazoxide at 30 microM, inhibited by 50 microM glibenclamide or 150 microM 5-hydroxydecanoic acid, and was not affected by the plasma membrane ATP-regulated potassium-channel blocker HMR1098 at 100 microM. We observed that the mitoK(ATP) channel was blocked by quinine in the micromolar concentration range. The inhibition by quinine was additionally verified with the use of 86Rb+ flux experiments and submitochondrial particles. Quinine inhibited binding of the sulfonylurea derivative [3H]glibenclamide to the inner mitochondrial membrane. We conclude that quinine inhibits the cardiac mitoK(ATP) channel by acting on the mitochondrial sulfonylurea receptor.

Animals↗

PubMed2005

Catalysis of NADH-->NADP+ transhydrogenation by adult Hymenolepis diminuta mitochondria.

Hymenolepis diminuta mitochondria catalyze nonenergy-linked and energy-linked NADH-->NADP(+) transhydrogenations, with the latter driven by electron-transport dependent NADH oxidation (electron transport-driven, ETD) or ATP hydrolysis (ATP-driven, ATPD). Using submitochondrial particles, NADH-->NADP(+) transhydrogenations were characterized further. ETD and ATPD reactions were enhanced by bovine serum albumin (BSA) and were inhibited by N,N'-dicyclohexylcarbodiimide (DCCD), carbonyl cyanide 3-chlorophenylhydrazone (CCCP), carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP), and niclosamide. The nonenergy-linked reaction was unaffected by these additives. Except for DCCD inhibition of the ATPD reaction, BSA mitigated inhibitor effects on energy-linked activities. BSA enhanced NADH oxidase (but not ATPase) activity. Although DCCD inhibited NADH oxidase and ATPase, BSA only lessened oxidase inhibition. With protonophores, an increase in NADH oxidase (but not ATPase) activity was suggested. Oxidase inhibition by rotenone was unaffected by BSA. The ATP-hydrolyzed/NADPH-formed for the ATPD reaction was almost unity. A model for H. diminuta energy-linked transhydrogenation is presented.

Animals↗

PubMed2005

Generation of superoxide-radical by the NADH:ubiquinone oxidoreductase of heart mitochondria.

Besides major NADH-, succinate-, and other substrate oxidase reactions resulting in four-electron reduction of oxygen to water, the mitochondrial respiratory chain catalyzes one-electron reduction of oxygen to superoxide radical O(2)(-.) followed by formation of hydrogen peroxide. In this paper the superoxide generation by Complex I in tightly coupled bovine heart submitochondrial particles is quantitatively characterized. The rate of superoxide formation during Deltamu(H(+))-controlled respiration with succinate depends linearly on oxygen concentration and contributes approximately 0.4% of the overall oxidase activity at saturating (0.25 mM) oxygen. The major part of one-electron oxygen reduction during succinate oxidation (approximately 80%) proceeds via Complex I at the expense of its Deltamu(H(+))-dependent reduction (reverse electron transfer). At saturating NADH the rate of O(2)(-.) formation is substantially smaller than that with succinate as the substrate. In contrast to NADH oxidase, the rate-substrate concentration dependence for the superoxide production shows a maximum at low (approximately 50 microM) concentrations of NADH. NAD+ and NADH inhibit the succinate-supported superoxide generation. Deactivation of Complex I results in almost complete loss of its NADH-ubiquinone reductase activity and in increase in NADH-dependent superoxide generation. A model is proposed according to which complex I has two redox active nucleotide binding sites. One site (F) serves as an entry for the NADH oxidation and the other one (R) serves as an exit during either the succinate-supported NAD+ reduction or superoxide generation or NADH-ferricyanide reductase reaction.

Animals↗

PubMed2004

Interconversion between dimers and monomers of endogenous mitochondrial F1-inhibitor protein complexes and the release of the inhibitor protein. Spectroscopic characteristics of the complexes.

The F1-inhibitor protein complex (F1-IP) was purified from heart submitochondrial particles. Size exclusion chromatography of the endogenous complex showed that it contains dimers (D) and monomers (M) of F1-IP. Further chromatographic analysis showed that D and M interconvert. At high protein concentrations, the interconversion reaction is shifted toward the D species. The release of the inhibiting action of IP is faster at low than at high protein concentrations. During activation of F1, the M species accumulates through a process that is faster than the release of IP from F1. These findings indicate that the activation of F1-IP involves the transformation of D into M, which subsequently loses IP. The spectroscopic characteristics of D, M, and free F1 show that the binding of IP and dimerization modifies the fluorescence intensity of tyrosine residues and that of the single tryptophan of F1 which is far from the IP binding site.

Animals↗

PubMed1983

An acyl-thioesterase from yeast mitochondria.

A previously unstudied acyl-coenzyme A thioesterase activity has been demonstrated in submitochondrial particles from Saccharomyces cerevisiae. The preferred substrate for the enzyme activity is oleoyl-coenzyme A. Tests with inhibitors of the thioesterase showed that, in addition to common thiol inhibitors, the oxidative phosphorylation inhibitors oligomycin and venturicidin also blocked thioesterase activity. Purification of the enzyme catalyzing this activity revealed that thioesterase copurified with mitochondrial ATPase. When thioesterase was isolated from oxidative phosphorylation mutants selected for resistance to these two inhibitors, thioesterase activity was also resistant. The results suggest that thioester hydrolysis may be catalyzed by components associated with the isolated ATPase complex. Further attempts to link this activity to in vivo function of ATPase were not successful.

Ethylmaleimide↗