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PubMed1983

[Is there anionic ATPase in the nuclei of animal cells?].

The nuclei of the rat liver, heart, thymus and of the mouse liver isolated in sucrose gradient reveal ATPase sensitive to bicarbonate, sulfite, azide and thiocyanate. The admixture of mitochondria and submitochondrial particles in the nuclear preparation was found negligible, which could not contribute to the anion ATPase in the nuclei. This was demonstrated by the calculation and by the introducing of mitochondria into the nuclear preparations.

Adenosine Triphosphatases↗
PubMed1983

Assembly of F1-ATPase in isolated mitochondria.

The assembly of the proton-translocating ATPase complex was studied in isolated mitochondria by incubating yeast mitochondria with radiolabeled precursors of mitochondrial proteins which had been made in a cell-free protein synthesis system. Following such an incubation, the ATPase complex (F1F0) was isolated. Newly assembled F1-ATPase was detected by autoradiography of the isolated enzyme, only peptide subunits which had been made in vitro and imported into the isolated mitochondria could be radioactive. Incorporation of radiolabeled ATPase subunits into the enzyme does not occur in the presence of an uncoupler of oxidative phosphorylation or of a divalent metal chelator, nor does it occur in submitochondrial particles rather than intact mitochondria. Incorporation of labeled ATPase subunits into the enzyme can be completed by unlabeled subunits, provided the unlabeled proteins are added before the mitochondria are incubated with radioactive precursors. These findings suggest that F1-ATPase is assembled from a pool of subunits in mitochondria.

Antigen-Antibody Complex↗
PubMedDate not supplied

[Effect of physico-chemical factors on anion-sensitive ATPase activity].

Effects of temperature, pH and anions on the ATPase activity of submitochondrial particles of rat liver, rat heart, mouse liver, of red blood cell membranes, and of soluble enzyme of rat liver, mouse liver mitochondria were studied. The temperature relationships of membrane-bound and soluble ATPases have the breaks at 18-21 degrees C and 30-32 degrees C. These breaks were not shifted by sulfite, thiocyanate, methanol, glycerol and GTP. The pH changes from 6.0 to 8.5 produced no effect on the temperature relationships of ATPase activities but, strongly influenced the rate of ATPase reaction. The conformity between the obtained data and earlier proposed mechanism of anion control over anion-sensitive ATPase activity was discussed.

Adenosine Triphosphatases↗
PubMed1984

Demonstration of organ specific antibodies against heart mitochondria (anti-M7) in sera from patients with some forms of heart diseases.

Using submitochondrial particles (SMP) from beef heart, pig kidney and rat liver in the ELISA, we detected partial organ specific anti-mitochondrial antibodies (AMA) against heart and kidney SMP in sera from patients with different forms of cardiomyopathies. Serum samples from 50 of 159 patients with congestive or hypertrophic cardiomyopathy (31%) and from two of 15 patients with acute myocarditis (13%) were AMA positive. These AMA could be clearly differentiated from other known AMA (anti-M1-M6) and were therefore named anti-M7. Thirteen of the 52 sera (25%) reacted only with heart SMP (type a) and 39 showed a cross-reaction with kidney, lung and pancreas mitochondria (type b). However, using liver SMP, no positive reaction was found. The anti-M7 type a and b activity was abolished completely by absorption with heart SMP. The anti-M7 antibodies were directed against an antigen which co-purified with the inner mitochondrial membrane and had a molecular weight of 67,000-72,000. They seem to be confined to some forms of cardiomyopathies and myocarditis of unknown aetiology and were not detected in sera from patients with other diseases.

Animals↗
PubMed1981

Fatty acyl coenzyme A-sensitive adenine nucleotide transport in a reconstituted liposome system.

The adenine nucleotide translocase was purified from bovine heart mitochondria and incorporated into membranes of phospholipid liposomes. The rate of transport of the adenine nucleotides was competitively inhibited by oleoyl coenzyme A with an approximate Ki of 1.0 microM. Significant inhibition was limited to those fatty acyl coenzyme A esters which are carnitine dependent for their oxidation in isolated mitochondria. Octanoyl coenzyme A was almost completely inactive as was palmitic acid and palmitoyl carnitine. By comparing the inhibitory characteristics of carboxyatractylate and bongkrekic acid with those of oleoyl-CoA, it was determined that the fatty acyl-CoA esters could produce inhibition whether the carrier was inserted into the liposome in either the conventional (65%) or reverse (30%) orientation. The results demonstrate that the interaction of long chain fatty acyl-CoA esters with the ADP/ATP carrier in a purified reconstituted system mimics their effects with isolated mitochondria and inverted submitochondrial particles. In general, these findings are consistent with the role of acyl-CoA esters acting as natural ligands and biological effectors of the translocator.

Acyl Coenzyme A↗
PubMed1983

Topographical orientation of complex III in the yeast mitochondrial membrane.

The orientation of the different subunits of complex III in the yeast inner mitochondrial membrane has been investigated by several different approaches. Immunoinhibition studies of cytochrome c reductase activity in intact mitoplasts and submitochondrial particles using IgG obtained from specific antisera against complex III, the iron-sulfur protein, core protein I, and core protein II suggested a transmembranous orientation of the complex with the antigenic sites of the iron-sulfur protein exposed on the cytoplasmic surface of the membrane. A lack of immunoinhibition was observed with the IgG against either core protein suggesting that these proteins may not be involved in catalysis. Digestion of mitoplasts with chymotrypsin indicated that the protein mass of cytochromes b and c1 protrudes from the cytoplasmic surface of the membrane; however, the hemes of cytochrome b appear to be buried within the membrane while the heme of cytochrome c1 is partially exposed on the chymotrypsin-sensitive portion of the polypeptide. By contrast, the iron-sulfur protein does not protrude from the membrane as it is completely resistant to chymotrypsin digestion. Labeling with the hydrophilic membrane-impermeant probe diazobenzenesulfonate suggests that core protein II is exposed on both sides of the membrane but protrudes into the matrix; while core protein I is within the membrane. Immunoprecipitation studies of sodium dodecyl sulfate and Triton X-100-solubilized mitochondria with subunit-specific antisera suggest that cytochromes b and c1 and core protein I are tightly associated in complex III. By contrast, the iron-sulfur protein and core protein II are loosely associated with the other subunits of the complex such that they are dissociated by low concentrations of detergent.

Chymotrypsin↗
PubMed1983

Haemoglobin potentiates the respiration-inhibitory action of lipoxygenases via its pseudolipohydroperoxidase activity.

The inhibition of the NADH oxidase and of the succinate-cytochrome c oxidoreductase activities of beef heart submitochondrial particles (ETP) induced by reticulocyte lipoxygenase is strongly potentiated by haemoglobin added simultaneously or subsequently to lipoxygenase. Half-maximal potentiation was observed with 0.9 microM haemoglobin. Haemoglobin augments also the lipoxygenase-induced loss of acid-labile sulphur in ETP not related to respiratory inhibition. Soybean lipoxygenase produces only weak respiratory inhibition even at high concentrations in the absence of haemoglobin; strong inhibition is obtained, however, in the presence of haemoglobin. Among other haem compounds tested only free haemin but not cytochrome c and catalase exhibit identical effects. The action of haem compounds on the system ETP plus lipoxygenase is accompanied by their destruction. The experimental evidence indicates that the effects of haemoglobin described here are due to its ability to decompose catalytically hydroperoxy lipids generated by lipoxygenase. This catalytic property (pseudolipohydroperoxidase activity) was demonstrated with 13L-hydroperoxylinoleic acid as substrate. The relations between the various catalytic actions of haemoglobin related to lipid peroxidation are discussed.

Animals↗
PubMed1981

Structural preferences for the binding of chromium nucleotides by beef heart mitochondrial ATPase.

The mono- and bidentate forms of adenosine 5'-diphosphate, chromium (III) salt (CrADP) were separated using Sephadex G-10 column chromatography. The isomeric purity of the two forms was monitored using high voltage electrophoresis and column chromatography. The same techniques were employed to assess the purity of the mono-, bi-, and tridentate forms of adenosine 5'-triphosphate, chromium (III) salt (CrATP). Distinct differences in the interaction of beef heart mitochondrial ATPase with the various isomers of chromium nucleotides were seen in kinetic studies. Monodentate CrADP was a competitive inhibitor of the ATP hydrolysis activity of both purified ATPase and submitochondrial particles. However, when ITPase activity was examined, noncompetitive inhibition was observed. The bidentate isomer of CrADP did not affect ATPase activity. Enzymatic synthesis of the transition state analog of ATP synthesis and hydrolysis, Pi-CrADP occurred exclusively with the monodentate isomer of CrADP. It was also found that only the mono- and tridentate forms of CrATP were potent inhibitors of ATP hydrolysis by beef heart mitochondrial ATPase. These results are discussed in terms of possible ATP synthesis and hydrolysis mechanisms.

Adenosine Diphosphate↗
PubMed1984

Adriamycin and derivatives interaction with the mitochondrial membrane: O2 consumption and free radicals formation.

Adriamycin induces the formation of semiquinone free radicals, O(2) and OH. species, in beef heart intact mitochondria, submitochondrial particles and complex I-III containing proteoliposomes. Free radicals were detected by the use of Electron Spin Resonance (ESR) spectroscopy with the spin trapping method. However, to observe transient oxygen species in intact mitochondria, a flow technique was mandatory. ESR results were compared with oxygen consumption measurements. Since free radicals could be involved in the mechanism of the adriamycin induced cardiotoxicity, it was essential to design new adriamycin derivatives which do not generate radicals. From the study of two adriamycin analogs (N-acetyl-adriamycin and 5-Iminodaunorubicin), it was shown that oxygen radicals formation require both the binding of the drug to the mitochondrial membrane and a quinone function associated with the drug structure. The data reported here might be useful in the synthesis of less cardiotoxic compounds.

Animals↗
PubMed1983

Isocitrate oxidation in dog heart mitochondria under anoxic conditions.

The roles of NAD- Specific Isocitrate Dehydrogenase (NAD- IDH) (EC 1.1.1.4), NADP- Specific Isocitrate Dehydrogenase (NADP- IDH) (EC 1.1.1.42) and Piridin Nucleotide Transhydrogenase (Transhydrogenase) (EC 1.6.1.1) in the mitochondrial oxidation of isocitrate through the respiratory chain in conditions of normal and increased energy requirements have been studied in submitochondrial particles isolated from healthy and ischemic dog hearts. The activities of both, NAD- IDH and NADP- IDH were increased in conditions of anoxia, while Transhydrogenase remained unchanged. The results obtained showed that the mitochondrial oxidation of isocitrate in dog myocardium occurs mainly through the NAD- IDH pathway in normoxic and anoxic conditions.

Animals↗
PubMed1982

On the role of factor B and oligomycin on generation and discharge of the proton gradient.

Bovine mitochondrial coupling factor B (FB) stimulates oxidative phosphorylation as well as other energy-linked reactions which are supported by ATP hydrolysis. Extraction of FB from submitochondrial particles results in a decrease in ATP-dependent proton translocation (delta pH) and binding of the voltage-sensitive dye, oxonol VI. Reconstitution of deficient particles with FB restores ATP-dependent proton translocation and oxonol binding but has little effect on oxonol binding supported by respiratory substrates.l In contrast, low levels of oligomycin stimulate oxonol binding supported by either ATP or NADH. In the case of oligomycin, the stimulatory effect is associated with a decrease in the rate of discharge of the proton gradient, but the depletion of FB or its restoration has no detectable effect on the discharge rate. The data indicate that the primary effect of FB is upon the rate of H+ translocation coupled to ATP hydrolysis, while that of low oligomycin is on the H+ permeability of the membrane.

Animals↗
PubMed1981

The interaction of a quinone pigment, xanthomegnin, with the mitochondrial respiratory chain.

The interaction of xanthomegnin, a quinone pigment, with the mitochondrial respiratory chain was demonstrated. Xanthomegnin was reduced by succinate, in the presence of submitochondrial particles or mitochondria, only after all oxygen had been consumed in the system, and the reduction was inhibited by antimycin A or KCN. Xanthomegnin was immediately reduced by NADH in a similar system, the reduced xanthomegnin was reoxidized by oxygen but the reduction by NADH was not inhibited by antimycin A or KCN. Xanthomegnin was also immediately reduced by NADH catalyzed by a purified particulate NADH dehydrogenase complex showing a molar ratio of 2 moles NADH for one mole of xanthomegnin. Reoxidation of the reduced pigment by oxygen occurred in this system. Oxygen consumption was accelerated when xanthomegnin was added to a reaction medium containing NADH, NADH segment and cytochrome c oxidase. Subsequent addition of cytochrome c resulted in a further marked acceleration of oxygen consumption. These results suggest that xanthomegnin interacts with the NAD-linked respiratory chain to produce a xanthomegnin shunt, but this does not occur with the succinate-linked chain.

Animals↗
PubMed1993

Characterization of cysteine residues of mitochondrial ADP/ATP carrier with the SH-reagents eosin 5-maleimide and N-ethylmaleimide.

The effects of the membrane-impermeable fluorescent sulfhydryl reagent eosin 5-maleimide (EMA) and the membrane-permeable sulfhydryl reagent N-ethylmaleimide (NEM) on ADP transport via the ADP/ATP carrier and their labeling sites in the carrier were studied in bovine heart submitochondrial particles. Of the 4 cysteine residues in the carrier, EMA labeled Cys159 very rapidly, Cys56 slowly, and Cys256 very slowly and did not label Cys128. Its labeling of Cys159 was associated with inhibition of the ADP transport, suggesting that the peptide segment containing Cys159 is involved in the transport of adenine nucleotides. In contrast to the very rapid binding of EMA to Cys159, NEM bound to Cys56 more slowly and labeled Cys159 and Cys256 much more slowly. Like EMA, it did not react with Cys128. The labeling of Cys56 with NEM also inhibited ADP transport. From these results, the locations of these cysteine residues in the ADP/ATP carrier are discussed in relation to the transport of adenine nucleotides mediated by the ADP/ATP carrier.

Animals↗
PubMed1975

[Action of the systemic fungicide dexon on several NADH dehydrogenases].

The fungicide dexon (p-dimethylaminobenzenediazosulfonate, Na-salt) inhibits the NADH oxidase activity of submitochondrial particles (ETP) from beef heart (semi-inhibition concentration 1.4 muM), while the succinate oxidase activity is unaffected. Measurements of the activity of several enzymatic partial reactions of the respiratory chain of ETP suggest that dexon acts directly on the flavine of NADH dehydrogenase. Soluble NADH-cytochrome c-oxidoreductase (MAHLER) and rotenone-insensitive NADH ubiquinone reductase are also inhibited by dexon. At low concentrations of dexon, inhibition of ETP starts slowly only after addition of NADH. Preincubation without NADH increases the amount of inhibition, but does not prevent the time delay. It is assumed that an electron flux through the respiratory chain, or reduction of flavine is prerequisite for the reaction of dexon with the action site. Furthermore, dexon inhibits the NADH dehydrogenase located at the outer surface of the inner membrane of plant mitochondria, accessible to extramitochondrial NADH and insensitive to rotenone, as has been shown on isolated mitochondria from cauliflower (Brassica oleracea L). In addition, dexon inhibits selectively the NADH dehydrogenase of the DT diaphorase (ERNSTER) from rat liver cytosol. In contrast, the dicoumarol-insensitive NADH dehydrogenase (ZINSMEYER et al.) from rat liver cytosol, the NADH-cytochrome b5-reductase (STRITTMATTER) from rat liver microsomes, the rotenone-insensitive NADH-cytochrome c-oxidoreductase of the outer membrane of rat liver mitochondria, soluble NADH-oxidase from Escherichia coli, and NADH-dehydrogenase from human erythrocytes are not inhibited. The results suggest that dexon is a group reagent to certain pyridine nucleotide-dependent flavine enzymes.

Animals↗
PubMed1977

Studies on the kinetic mechanism of oxidative phosphorylation.

The kinetics of the synthesis of ATP from ADP and Pi by beef heart submitochondrial particles were examined. When Pi was the variable substrate positive cooperativity was observed, whereas if ADP was varied, linear double reciprocal plots were obtained. The analog of Pi, thiophosphate, was a noncompetitive inhibitor of ATP synthesis with respect to ADP, while the analog of ADP, AMP (CH2)P, was an uncompetitive Pi leads to ATP exchange inhibitor. The kinetics of the initial velocity isotopic exchanges of oxidative phosphorylation were also examined. When the Pi leads to ATP exchange was examined, it was found that if ADP concentration was held constant while ATP and Pi concentrations were varied at a constant ratio, linear double reciprocal plots were obtained. However, if Pi concentration was held constant and ADP and ATP concentrations were varied at constant ratio, apparent substrate inhibition was observed. The 2, 4-dinitrophenol-sensitive ADP leads to ATP exchange showed linear double reciprocal plots regardless of which components were varied. These results are interpreted to indicate that in the direction of ATP synthesis, the reaction is ordered, with Pi adding to the enzyme before ADP addition.

Adenosine Diphosphate↗
PubMed1993

Effect of polyamines on mitochondrial F-ATPase from Crithidia fasciculata and Trypanosoma cruzi.

ATP hydrolysis by Crithidia fasciculata mitochondrial ATPase was studied through the use of submitochondrial particles and the soluble enzyme. (a) ATP hydrolysis by these preparations was inhibited by spermine but not by spermidine or putrescine. (b) The ATPase activity inhibited by spermine was partially recovered when excess Mg2+ was added to the reaction mixture. (c) When polyamines were present throughout the preparation of the mitochondrial membranes, the membrane-bound ATPase was irreversibly inactivated. The polyamine effect decreased in the order spermine > putrescine > spermidine. (d) The spermidine or putrescine pre-treated membranes oxidized succinate at a faster rate than the control ones. (e) Trypanosoma cruzi F-ATPase was inhibited by polyamines in the same manner as the C. fasciculata enzyme.

Adenosine Triphosphatases↗
PubMed1995

[Protein composition of venoms from several species of tropical ants and their effect on mitochondrial H+-ATPase].

Protein compositions of venoms of South-American stinging ants, Ectatomma tuberculatum, Paraponera clavata (subfamily Ponerinae), and "tangarana" were analyzed. The venom of E. tuberculatum displayed the most complex protein composition (more than 15 polypeptides). The water-soluble fraction of the venoms of P. clavata and "tangarana" contained acidic proteins (pI < 3.5 to 5.2), whereas the venom of E. tuberculatum contained predominantly basic proteins (pI 8 to > 9.5). N-Terminal residues and N-terminal sequences of a number of polypeptides were determined. High-molecular-mass polypeptides of the P. clavata venom slightly stimulated the ATPase activity of mitochondrial F1-ATPase. Low-molecular-mass nonprotein components of this venom significantly inhibited the ATPase activity of submitochondrial particles and F1-ATPase from bovine heart mitochondria. The venoms of E. tuberculatum and "tangarana" produced no effect on the ATPase activity.

Amino Acid Sequence↗
PubMed1977

An alternating site sequence for oxidative phosphorylation suggested by measurement of substrate binding patterns and exchange reaction inhibitions.

Catalysis by beef heart submitochondrial particles of the medium Pi in equilibrium HOH, Pi in equilibrium ATP, and the ATP in equilibrium HOH exchanges is strongly inhibited while the ATPase and intermediate Pi in equilibrium HOH exchange are accelerated when medium ADP is removed by pyruvate kinase action. Arsenate readily blocks completely the Pi in equilibrium ATP and medium Pi in equilibrium HOH exchange reactions, but not the ATP in equilibrium HOH exchange reaction. The residual ATP in equilibrium HOH exchange in presence of arsenate is inhibited by 2,4-dinitrophenol. These results and other data are explained by an alternating site model for oxidative phosphorylation. In this model during net oxidative phosphorylation ATP is formed at one site but is transitorily tightly bound and not released until ADP and Pi bind at a second site and the membrane ATPase complex is energized. Under conditions of net ATP hydrolysis, ATP binding at one site is accompanied by hydrolysis of the transitorily tightly bound ATP as a second site. Attractive features are only one site of input for conformational energization of the membrane ATPase, a single conformational transition that accounts for both the promotion of ADP and Pi binding in a competent mode and the release of tightly bound ATP, and a symmetry of catalytic sites. The Pi in equilibrium ATP exchange is not inhibited by increase in MgADP and MgATP at constant ratios, and the energy-linked ADP in equilibrium ATP exchange is not inhibited by increased concentrations of MgATP and Pi at a constant ratio. Such exchange patterns indicate a random binding and release of ADP and Pi.

Adenosine Triphosphate↗