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 1,099 records · Page 61Linked to original sources
PubMed1983

Effect of b-c1-site inhibitors on the midpoint potentials of mitochondrial cytochromes b.

Anaerobic potentiometric titrations of b cytochromes have been carried out in beef heart submitochondrial particles in the presence of several specific inhibitors of electron transfer through the b-c1-site of the respiratory chain. Whereas antimycin shows no significant effect on the titration curve of cytochrome b-562, NoHOQnO is found to shift the Em of b-562 by 20-30 mV to the positive. Funiculosin raises the Em of b-562 by greater than 100 mV and also appears to bring about a minor shift of b-566 midpoint potential. In the presence of myxothiazol, both b cytochromes titrate with Em values 15-30 mV more positive than in the control.

Animals↗
PubMed1983

Effect of electron transfer inhibitors on superoxide generation in the cytochrome bc1 site of the mitochondrial respiratory chain.

Antimycin, 2-nonyl-4-hydroxyquinoline N-oxide and funiculosin induce O.2(-) generation by submitochondrial particles oxidizing succinate, whereas KCN, mucidin, myxothiazol or 2,3-dimercaptopropanol inhibit O.2(-) generation. Thenoyltrifluoroacetone does not induce superoxide production by itself but slightly stimulates the reaction initiated by antimycin. The results indicate that auto-oxidation of unstable ubisemiquinone formed in centre o of the Q-cycle generates most of the O.2(-) radicals in the cytochrome bc1-site of the mitochondrial respiratory chain.

Alkenes↗
PubMed1984

Electron microscopy of beef heart mitochondrial F1-ATPase.

The quaternary structure of isolated and membrane-bound F1-ATPase (submitochondrial particles) has been studied by electron microscopy. A model of the molecule has been proposed: six protein masses are arranged in two layers approximately at the vertices of a triangular antiprism. Computer averaging of the images showed that the frontal view of the molecule can be approximately characterized by mirror plane symmetry.

Animals↗
PubMed1985

Monoclonal antibodies to mitochondrial coupling factor B.

Two monoclonal antibodies (MAb I and IV) have been prepared which showed high and specific reactions towards bovine heart mitochondrial coupling factor B (FB). Both have been identified as sub-type IgG1 of mouse immunoglobulins. MAb I reacts with purified and functionally active FB, alkylated or oxidized forms of FB and even with peptides formed on digestion of FB with trypsin. When used together, MAb I and IV reacted with FB in immunoblots of normal and urea treated samples of mitochondria, submitochondrial particles, ammonia-EDTA extracted particles, and H+-ATPase. Both MAbs inhibited FB-stimulated ATP-dependent reverse electron flow activity when FB was incubated with the antibody either before or after its addition to FB-deficient AE-particles. Reactivity of MAb I towards FB declined upon exposure of FB to guanidine HC1 while reactivity of MAb IV remained unaltered.

Animals↗
PubMed1985

Exploration of nucleotide binding sites in the mitochondrial membrane by 2-azido-[alpha-32P]ADP.

The ADP/ATP carrier of beef heart mitochondria is able to bind 2-azido-[alpha-32P]ADP in the dark with a Kd value of congruent to 8 microM. 2-Azido ADP is not transported and it inhibits ADP transport and ADP binding. Photoirradiation of beef heart mitochondria with 2-azido-[alpha-32P]ADP results mainly in photolabeling of the ADP/ATP carrier protein; photolabeling is prevented by carboxyatractyloside, a specific inhibitor of ADP/ATP transport. Upon photoirradiation of inside-out submitochondrial particles with 2-azido-[alpha-32P]ADP, both the ADP/ATP carrier and the beta subunit of the membrane-bound F1-ATPase are covalently labeled. The binding specificity of 2-azido-[alpha-32P]ADP for the beta subunit of F1-ATPase is ascertained by prevention of photolabeling of isolated F1 by preincubation with an excess of ADP.

Adenosine Diphosphate↗
PubMed1985

The oxidation of sulfhydryl groups in mitochondrial F1-ATPase decreases the rate of its inactivation by the natural protein inhibitor.

The oxidants of the SH groups (o-iodozobenzoate, oxidized glutathione, etc.) and the divalent cations of some metals (Zn2+ and Cd2+) significantly slow down the rate of inactivation by the protein inhibitor of the isolated F1-ATPase and ATPase in submitochondrial particles. Modification of SH groups in the ATPase does not change the rate of inactivation but completely prevents the effect of oxidants.

Animals↗
PubMed1986

Characterisation of phosphate binding to mitochondrial and bacterial membrane-bound ATP synthase by studies of inhibition with 4-chloro-7-nitrobenzofurazan.

The effect of phosphate on the inhibition by 4-chloro-7-nitrobenzofurazan of the ATPase activity of the proton-translocating ATP synthase in heart submitochondrial particles was investigated. Binding of phosphate protected strongly against the inhibition. A dissociation constant of 0.2 mM was determined for the enzyme X Pi complex and shown to be independent of pH in the range 7.0-8.0. The protective effect of phosphate was mimicked by arsenate but not by sulphate or malonate. Similar results were obtained for the enzyme from Paracoccus denitrificans. 2,4-Dinitrophenol enhanced phosphate binding to the mitochondrial enzyme since the protective effect of phosphate was increased. The data are compatible with protection arising from binding of phosphate to a catalytic site.

2,4-Dinitrophenol↗
PubMed1989

Inhibitory domain-specific antibodies to cytochrome P-450scc.

Highly specific antibodies to cytochrome P-450scc and its F1 and F2 fragments, representing N- and C-terminal sequences of the hemeprotein respectively, were raised in rabbits. These antibodies were found to be inhibitory (up to 50-90%) for the cholesterol transformation into pregnenolone in the reconstituted system, indicating the involvement of both F1 and F2 domains formed by the respective fragments in monooxygenase catalysis. Cytochrome P-450scc in mitoplasts is not accessible for trypsin as revealed by immunological techniques. However, the treatment of submitochondrial particles with trypsin results in two main fragments identified by immunoblotting in the presence of the monospecific antibodies as F1 and F2 fragments. This indicates that the trypsin sensitive 250-257 region in cytochrome P-450scc molecule connecting both domains is exposed to the matrix side of the inner mitochondrial membrane.

Adrenal Cortex↗
PubMed1983

Cuvette and flow system for simultaneous determination of optical density and oxygen concentration.

The major components of the device for semiautomatic measurement of oxygen consumption and optical density changes are a thermostated glass reservoir of 50-250 ml for the reaction mixture, a roller pump to transport the reaction mixture from the reservoir into the measuring cuvette, and a stoppered glass cuvette equipped with a Clark type electrode. The glass cuvette (0.525 ml) is square shaped (the interior section 6 X 6 mm). The lower part housing the magnetic stirrer has a side aperture for the oxygen electrode. The upper part of the cuvette is cylinder shaped. The stopper is fitted in this part. The stopper made of lucite protrudes 15 mm into the cuvette. The access and the removal of the reaction mixture to/from the cuvette is ensured by three different channels machinated into the body of the stopper. The device adaptable to Eppendorf spectralline photometer may be used in the study of oxidative phosphorylation on intact mitochondria or submitochondrial particles, or of any oxygen consuming system in which one reagent or reaction product can be monitored photometrically.

Densitometry↗
PubMed1992

Steady-state kinetic properties of FoF1-ATPase: the pH effect.

1. The kinetic properties of FoF1-ATPase from submitochondrial particles isolated from rat heart were studied, with emphasis to the pH effect. The velocity data were treated according to the Hill equation, and the results were discussed on the basis of the knowledge on the soluble F1-ATPase properties. 2. Three kinetic phases were observed in the range of pH 6.0-8.5, with apparent dissociation constant values (K0.5) of 0.001, 0.04 and 1.5 mM (respectively sites I, II and III) at pH 7.0. Their contribution to the total activity of the enzyme were pH-dependent on the range of 6.0-7.0, but not from 7.0 to 8.5, where the maximal velocity (V) for site III was some 4-fold larger than for site II, and the total V of sites II and III was some 40-fold larger than V assumed for site I. Therefore, two catalytic sites seem to participate significantly in the catalysis at steady-state condition. 3. Azide increased the sites II and III K0.5 values as well as decreased the site III V. In the presence of bicarbonate these two sites were not distinguishable, and the kinetic parameters at pH 7.0 were similar to those for sites II and III combined. Both azide and bicarbonate did not have a significant effect on site I, and this behavior was not pH-dependent. 4. The studies on the effect of pH on the kinetic parameters showed the following results: (1) the optimum pH for V was around 8.5; (2) decrease in the K0.5 values at pH below 7.0 for site II, and increase at pH over 7.0 for sites II and III; (3) in the pH range of 6.0-8.5 the Hill coefficient increased for site II, decreased for site III, and an intermediary effect was observed for the sites II and III combined, with a Michaelis-Menten behavior in the highest affinity pH, which was found in the physiological range.

Adenosine Triphosphate↗
PubMed1993

Strongyloides ratti: fumarate reductase and succinate dehydrogenase activities of infective larvae.

Submitochondrial particles prepared from axenised infective (L3) larvae of S. ratti (homogonic-strain) were assayed spectrophotometrically for fumarate reductase (FR) and succinate dehydrogenase (SDH) and their kinetic properties characterised. The S. ratti FR (pH 8.2; 37 degrees C) exhibited a maximum specific activity of 3.45 nmol (min)-1 (mg protein)-1 at a sodium fumarate concentration of 0.3 mM. Interestingly, the FR activity declined at fumarate concentrations greater than 0.3 mM. The mechanism of this unusual inhibitory effect requires further study. The S. ratti SDH (pH 8.2; 37 degrees C) showed a Vmax of 17.4 nmol (min)-1 (mg protein)-1; the Kmsucc was 0.5 mM. Although the SDH:FR ratio cannot predicate vectorial electron flow as would occur in vivo, an in vitro ratio of 5.04:1 was observed for SMPs derived from S. ratti L3 larvae.

Animals↗
PubMed1982

A direct binding assay for mitochondrial autoantibodies.

A direct binding assay for the detection of mitochondrial autoantibodies (AMA) is described. The method has been standardised to use as antigen 1 mg/ml submitochondrial particles which are absorbed on to the surface of LINBRO S-MVC-96 microtitration plates as the solid phase. 125I-labelled antihuman immunoglobulin is used as the second antibody. The sensitivity achieved is greatly increased compared with immunofluorescence and complement fixation methods, with good discrimination between AMA negative and positive sera. The assay is rapid and has the advantages of a primary binding method. Two variations of the method are described. The first is reported as a "binding index' which is calculated from the binding shown by an unknown serum at 2 dilutions, and would be suitable as a screening procedure. Binding curves of doubling dilutions of a test serum give, in addition to the binding index, a titre which is defined as that dilution at which binding returns to the level of a normal serum. This is a longer procedure and more suitable as a research method.

Animals↗
PubMed1988

Use of immunoblotting to characterize the mitochondrial antigens recognized by anti-mitochondrial autoantibodies.

Sera with anti-mitochondrial autoantibodies detected by indirect immunofluorescence and/or enzyme-linked immunosorbent assay (ELISA) were examined by immunoblotting against pig heart mitochondria. Seven types of reactions were defined, according to the pattern of the labelled bands. Type I sera reacted with 12 bands located within four zones. The most intensively labelled bands were located at 70, 67, 58, 63 and 43 kDa. Other types gave decreasing band numbers. When beef heart mitochondria were used, sera belonging to each of the above types had a profile of labelled bands which sometimes differed from those obtained with pig heart mitochondria. When the chloroform extracted F1-ATPase from beef heart mitochondria was used to prepare the immunoblots, primary biliary cirrhosis (PBC) sera with anti-mitochondria antibodies reacted with all the bands although zone A bands were less labelled. Rat liver mitochondria gave seven bands with type I sera among which the 57 and 35 kDa bands were specific for rat liver mitochondria, as shown by absorption tests. Sera of PBC patients were also tested in immunoblotting against rat liver subcellular fractions including mitoplasts, submitochondrial particles, inner membrane, outer membrane, matrix proteins and inter-membrane proteins. Antigenic bands of A and B zones were localized in the inner membrane and/or in the matrix proteins and the 35 kDa band in inter-membrane proteins. The outer membrane gave no reaction. The most frequent anti-mitochondrial autoantibody types in PBC were type II, then I, whilst for chronic active hepatitis type III was the most common. Type V was only seen in a patient suffering from a typical PBC. Some sera from patients with syphilis, collagenous colitis or progressive systemic sclerosis labelled one or two bands distinct from those labelled by the PBC sera. Sera from patients with drug-induced hepatitis with endoplasmic reticulum antibodies and with systemic lupus erythematosus were generally found negative by immunoblotting.

Animals↗
PubMed1982

Effect of thyroidectomy on the rat adrenal cortex enzyme activities involved in corticosterone and aldosterone biosynthesis.

The effect of thyroidectomy on corticosterone and aldosterone biosynthesis, in rat adrenal cortex, were investigated in vitro. Thyroidectomy slowed down by about 30% the activity of microsomal 21 hydroxylase and mitochondrial 11 beta hydroxylase, the two stages leading to corticosterone formation from progesterone. The plasma corticosterone concentration also diminished in thyroidectomized rat. The mitochondrial enzyme system catalyzing the conversion of corticosterone into aldosterone included both 18 hydroxylase and 180H dehydrogenase. In the absence of thyroid hormone, values of both enzyme activity slowed down by about 30%. Thus thyroidectomy induced a general decrease in all mitochondrial hydroxylation processes requiring NNADPH as energetic cofactor. Mitochondrial NADPH was mainly synthesized by the activity of NADP+ malic enzyme and pyridine nucleotide transhydrogenase; the activity of both enzymes was determined in submitochondrial particles from adrenal cortex of normal and thyroidectomized rats. The activity of NADP+ malic enzyme and non energy-dependent transhydrogenase in the direction of NADPH formation dropped significantly after thyroidectomy, thus reducing the amount of NADPH available for hydroxylating mechanisms. The results should be compared to the large rise in th cytosolic malic enzyme level caused by thyroidectomy. The latter also ensured that the transhydrogenase reaction did not vary in the direction of NADP+ formation. Further, the drop in NADPH synthesis after thyroidectomy was coupled with a decrease in phosphorylation rate of added ADPH by adrenal cortex mitochondria of thyroidectomized rat. These findings might account for the general decline in the energy-dependent processes involved in steroidogenesis, a decline mainly due to the lowering of the H+ ions gradient driving ATP and NADPH synthesis through electron transfer.

Adrenal Cortex↗
PubMed1988

Biochemical evidence that high concentrations of the antidepressant amoxapine may cause inhibition of mitochondrial electron transport.

Overdosage with the antidepressant amoxapine causes metabolic acidosis and may lead to brain damage and death. To better understand the metabolic disturbances caused by amoxapine overdose, its effects on three simple systems were studied: growth of Saccharomyces cerevisiae, mitochondrial energy metabolism, and an electron transport system in microsomal membranes. Growth of yeast on all substrates except lactate was inhibited by amoxapine at 50-100 micrograms ml-1. Growth on lactate was observed at 200 micrograms ml-1 of amoxapine. In beef heart mitochondria, amoxapine at 100 micrograms ml-1 inhibited reactions involving large sections of the electron transport chain. Energy-linked reactions in submitochondrial particles were also inhibited. Electron microscopy showed some disruption of the mitochondrial internal structure by amoxapine and a change from orthodox to condensed conformation. Microsomal NADH-cytochrome b5 reductase was inhibited by amoxapine, but at higher amoxapine concentrations than mitochondrial reactions. The results suggest amoxapine disrupts reactions of membrane-associated enzyme complexes, and mitochondrial energy conservation may be one of the first systems affected. We speculate that lactic acid accumulation in patients with amoxapine overdose may be caused by loss of electron acceptor activity in tissues.

Amoxapine↗
PubMed1992

In vitro and in vivo effect of methyl isocyanate on rat liver mitochondrial respiration.

Previous work has shown that irrespective of the route of exposure methyl isocyanate (MIC) caused acute lactic acidosis in rats (Jeevaratnam et al., Arch. Environ. Contam. Toxicol. 19, 314-319, 1990) and the hypoxia was of stagnant type due to tissue hypoperfusion resulting from hypovolemic hypotension in rabbits administered MIC subcutaneously (Jeevarathinam et al., Toxicology 51, 223-240, 1988). The present study was designed to investigate whether MIC could induce histotoxic hyperoxia through its effects on mitochondrial respiration. Male Wistar rats were used for liver mitochondrial and submitochondrial particle (SMP) preparation. Addition of MIC to tightly coupled mitochondria in vitro resulted in stimulation of state 4 respiration, abolition of respiratory control, decrease in ADP/O ratio, and inhibition of state 3 oxidation. The oxidation of NAD(+)-linked substrates (glutamate + malate) was more sensitive (five- to sixfold) to the inhibitory action of MIC than succinate while cytochrome oxidase remained unaffected. MIC induced twofold delay in the onset of anerobiosis, and cytochrome b reduction in SMP with NADH in vitro confirms inhibition of electron transport at complex I region. MIC also stimulated the ATPase activity in tightly coupled mitochondria while lipid peroxidation remained unaffected. As its hydrolysis products, methylamine and N,N'-dimethylurea failed to elicit any change in vitro; these effects reveal that MIC per se acts as an inhibitor of electron transport and a weak uncoupler. Administration of MIC sc at lethal dose caused a similar change only with NAD(+)-linked substrates, reflecting impairment of mitochondrial respiration at complex I region and thereby induction of histotoxic hypoxia in vivo.

Adenosine Diphosphate↗
PubMed1981

Mg2+-activated adenosine triphosphatase from Crithidia fasciculata: purification and inhibition by suramin and efrapeptin.

The mitochondrial Mg2+-activated adenosine triphosphatase (ATPase; EC 3.6.1.4) from the insect flagellate Crithidia fasciculata ATCC 11745 has been extracted from the membrane by chloroform treatment and purified to electrophoretic homogeneity by a method involving ammonium sulphate fractionation, gel filtration on Sephadex G-200 and DEAE-cellulose chromatography. The molecular weight of the native enzyme, determined by gel filtration, was about 350 000. Five subunits were detected by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate, with molecular weights of 54 000, 45 000, 35 000, 20 000 and 10 000. The membrane-bound, but not the soluble (F1) ATPase was inhibited by oligomycin and leucinostatin. Both forms of the enzyme were strongly inhibited by the antibiotic efrapeptin and the trypanocidal drug suramin. The inhibition by efrapeptin was of the mixed type, with double-reciprocal plots intersecting below the abscissa, as in the case of the enzyme present in beef heart submitochondrial particles. Suramin, on the other hand, acted as a non-competitive inhibitor of the membrane-bound ATPase and as a strictly competitive inhibitor of the purified F1 ATPase.

Adenosine Triphosphatases↗
PubMed1984

Electron transfer complexes of Ascaris suum muscle mitochondria: I. Characterization of NADH-cytochrome c reductase (complex I-III), with special reference to cytochrome localization.

An NADH-cytochrome c reductase (complex I-III) was isolated from Ascaris suum muscle mitochondria. The enzyme preparation catalyzed the reduction of 1.68 mumol cytochrome c min-1 mg-1 protein at 25 degrees C with NADH but not with NADPH, and retained its sensitivity to rotenone, piericidin A and 2-heptyl-4-hydroxyquinoline-N-oxide as with the submitochondrial particles. The isolated complex I-III, essentially free of succinate-cytochrome c reductase and cytochrome c oxidase, consisted of fourteen polypeptides with apparent molecular weights ranging from 76 000 to 12 000. The complex I-III contained three cytochromes, b-559.5, b-563 and c1-550.5 and Pigment-558 at concentrations of 1.28, 0.211, 1.23 and 0.321 nmol mg-1 protein, respectively. Cytochrome b-558, a major constituent cytochrome of Ascaris mitochondria and previously suggested to participate in the fumarate reductase system, was not fractionated in the complex I-III. Localization of the cytochromes in Ascaris electron transfer complexes is discussed.

Animals↗