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 1,729 records · Page 96Linked to original sources
PubMed1985

Respiratory control in mitochondria from Trypanosoma cruzi.

Phosphorylating mitochondrial membranes were obtained from Trypanosoma cruzi culture (epimastigote) forms. Using ADP as phosphate acceptor and succinate, sn-glycerol-3-phosphate, L-malate or ascorbate plus tetramethyl-p-phenylenediamine (TMPD) as oxidizable substrates, energy coupling sites II and III were detected, with respiratory control values in the range of 2.8-2.0. Carbonyl cyanide m-chlorophenylhydrazone and sonication uncoupled the respiratory control mechanism. Antimycin and cyanide partially inhibited succinate, sn-glycerol-3-phosphate and L-malate oxidation, while cyanide totally inhibited ascorbate + TMPD oxidation by the mitochondrial preparation. Succinate oxidation was inhibited by malonate and oxalacetate, but this latter was only effective with sonicated mitochondria. At variance with other substrates, NADH oxidation was not controlled by ADP concentration or inhibited by antimycin or cyanide. Rotenone failed to inhibit electron transfer in T. cruzi mitochondria.

Animals↗
PubMed1982

The reaction of the trifluoromethylphenylcarbamylated lysine-13 derivative of horse cytochrome c with cytochrome oxidase.

The kinetics of oxidation of horse cytochrome c and the trifluoromethylphenylcarbamylated lysine-13 derivative by cytochrome c oxidase (ferrocytochrome c: oxygen oxidoreductase, EC 1.9.3.1) were compared using both spectrophotometric and polarographic methods under different experimental conditions. The rate constants measured spectrophotometrically in 0.025 M tris-cacodylate buffers were similar with the two cytochrome at pH 7.8, but those with the derivative were slightly higher at pH 6. Rates measured with polarographic assays in these buffers were the same with the horse and the derivative cytochromes c at pH 6, but at pH 7.8 the rates with the derivative were less at cytochrome c concentrations between 0.05 and 0.5 micro M and were greater at higher concentrations. The pH optima in the polarographic assays of the derivative and the native pigments were different in 0.025 M Tris-cacodylate buffers; in spectrophotometric assays at pH 7.8 the trifluoromethylphenylcarbamylated lysine-13 cytochrome c showed a greater sensitivity to changes in ionic strength than did the native cytochrome. The variations in apparent Km and V values calculated from spectrophotometric and polarographic assays with the two cytochromes cannot be explained as due to changes in binding of cytochrome c to cytochrome oxidase. The large excess of O2 uptake seen in polarographic assays with horse cytochrome c over that expected from spectrophotometric measurements was not apparent with the trifluoromethylphenylcarbamylated lysine-13 derivative. Thus, the derivative seems to have decreased ability to form the combination of cytochrome c with the oxidase giving high turnover rates.

Animals↗
PubMed1985

An alkaline thiol proteinase in the liver mitochondria of bullfrog, Rana catesbeiana.

The mitoplasts were prepared from bullfrog (Rana catesbeiana) liver mitochondria by treatment with digitonin and were then separated into the matrix and inner membrane fractions. The matrix fraction thus obtained was free of lysosomal contaminations and exhibited a distinct proteinase activity. pH dependency of the matrix proteinase activity measured in the presence and absence of iodoacetamide revealed that the matrix contained at least two kinds of proteinase, a major alkaline thiol proteinase having an optimal pH at 8.5 and a minor neutral proteinase having an optimal pH at 7.5. The major matrix proteinase activity was strongly inhibited by leupeptin, chymostatin, antipain and E64-C, an inhibitor of Ca2+-dependent thiol proteinase, while it was scarcely affected by diethylpyrocarbonate. The activity was also inhibited by DTNB and p-chloromercuribenzoate. Addition of hydrocarbon compounds such as ethylene glycol, glycerol, Triton X-100 and poly (ethylene glycol) to the reaction mixture was found to decrease the matrix proteinase activity. Neither cytochrome c nor glutamate dehydrogenase was hydrolyzed when subjected to the matrix proteinase activity in vitro. On the other hand, cytochrome c oxidase was effectively hydrolyzed, and the enzyme associated with the mitochondrial innermembrane fragments was partially hydrolyzed by the major matrix proteinase activity.

Animals↗
PubMed1991

Evidence for an in vivo modification of mitochondrial proteins by coenzyme A.

Following denaturation of mitochondrial proteins by sodium dodecyl sulfate, a [1-14C]pantothenic acid-derived radioactivity proved to be acid precipitable in the outer membrane, the intermembrane space, the inner membrane and in the matrix of rat liver mitochondria, where it had the highest specific radioactivity of 541 +/- 29 cpm/100 micrograms protein. This tightly and/or covalently bound protein radioactivity could be released by incubation in the presence of dithioerythreitol; it was identified as [14C]coenzyme A by its HPLC retention time, its absorption spectrum and its radioactivity. This acid-stable and thiol-labile coenzyme A-binding apparently refers to specific protein binding sites. With the purified, homogeneous mitochondrial matrix enzymes acetyl-CoA acetyltransferase (acetoacetyl-CoA thiolase) (EC 2.3.1.9, acetyl-CoA:acetyl-CoA C-acetyltransferase) and 3-oxoacyl-CoA thiolase (EC 2.3.1.16) coenzyme A was found exclusively, e.g., in the modified, partially-active forms A1 und A2 of acetyl-CoA acetyltransferase and not in the unmodified fully-active enzyme. Thus it is evident that this coenzyme A modification is transient. We suggest that coenzyme A-modification is a signal involved in the assembly or the degradation process of distinct mitochondrial matrix proteins.

Acetyl-CoA C-Acetyltransferase↗
PubMed1982

Ionophores and intact cells. I. Valinomycin and nigericin act preferentially on mitochondria and not on the plasma membrane of Saccharomyces cerevisiae.

Valinomycin and nigericin prevented growth of 13 strains of the yeast Saccharomyces cerevisiae on non-fermentable substrate glycerol without affecting much fermentative growth on glucose. The two antibiotics did not induce swelling and lysis of yeast protoplasts in potassium acetate and did not modify uptake and release of Rb+ by the yeast cells. Both antibiotics were taken up by yeast cells at a relatively low rate. Nigericin accelerated the glucose-induced changes of fluorescence of a cyanine dye absorbed by yeast cells, which had been previously ascribed to a depolarization-repolarization cycle of the mitochondrial membrane. The data suggest that valinomycin and nigericin act as ionophores in the inner mitochondrial membrane and not in the plasma membrane of intact yeast cells.

Anti-Bacterial Agents↗
PubMed1990

Intermitochondrial junctions in a subpopulation of peripheral blood lymphocytes from healthy subjects.

This paper reports the observation of intermitochondrial junctions (IMJ) with a periodicity of 15.4 +/- 0.65 nm in peripheral blood lymphocytes of healthy subjects. The percentage of IMJ-containing cells appears constant (about 10% of examined lymphocytes) and is independent of the delay of fixation. Immunogold staining reveals that lymphocytes with IMJ exhibit a T-phenotype. IMJ have been reported in other types of tissues but, to our knowledge, have not been previously described in the blood cell. The signification of these structures is discussed.

Adult↗
PubMed1986

Intramitochondrial inclusions in the kidney of the pygmy mouse.

Intramitochondrial inclusions averaging 1000 A in diameter were observed in the cells of the proximal convoluted tubules in samples of kidneys from pygmy mice, Baiomys taylori. Electron microscopic study of unstained sections and mitochondrial fractions showed that these inclusions are lipid and found at a S.G. 1.37 in a linear sucrose gradient. Renal glycogen, inorganic phosphate and plasma sodium were significantly higher in the pygmy mouse and plasma calcium was lower, as compared with the laboratory mouse. We believe these intramitochondrial inclusions to be lipid which accumulates divalent cations, particularly calcium, which acts as a sodium pump allowing the pygmy mouse to conserve water and adapt to its environment.

Animals↗
PubMed1985

Utilization of intramitochondrial membrane cholesterol by cytochrome P-450-dependent cholesterol side-chain cleavage reaction in bovine adrenocortical mitochondria: steroidogenic and non-steroidogenic pools of cholesterol in the mitochondrial inner membranes.

Inner and outer submitochondrial membranes were prepared after disruption of malate-treated bovine adrenocortical mitochondria. It was found that a part of the endogenous cholesterol in the inner membrane (approx. 50%) was rapidly utilized by the cholesterol side-chain cleavage reaction. The utilization of cholesterol in the outer membrane, on the other hand, was inefficient and slow in spite of the fact that cholesterol concentration is higher in the outer than in the inner membrane. When the inner membrane prepared from untreated mitochondria was incubated for 20 min in the presence of a reconstituted cytochrome P-450-reducing system, the inner membrane cholesterol was depleted by approximately 70%. The half-life of the depletion reaction was 2-3 min. In addition, when the outer membrane plus the soluble fraction from the untreated mitochondria were added as a source of cholesterol to the inner membrane fraction, a marginal increase in the production of steroids was observed. From these results it is concluded that a portion of the inner membrane cholesterol can be steroidogenic, whereas the rest of the cholesterol is non-steroidogenic.

Adrenal Cortex↗
PubMed1986

Preparation and characterization of submitochondrial fractions from adrenal cells.

A method for preparing submitochondrial fractions from adrenocortical cells was developed by adapting a procedure that has been successful with yeast mitochondria. The method is based upon osmotic swelling, sonication and centrifugation in sucrose. The preparation yields highly purified fractions of outer membrane, intermembrane space, inner membrane and a less purified fraction of matrix. Recoveries are good so that 10(7) cells yield approximately 170 micrograms of inner membrane protein and 12 micrograms of outer membrane protein. Electron microscopy shows that the outer membrane fraction consists of vesicles (0.2-0.6 micron diameter) while inner membrane appears as densely packed sheets of membranous material. Two-dimensional polyacrylamide gels (isoelectric focusing followed by electrophoresis) of all the fractions give highly reproducible patterns of protein spots with Coomassie staining. Steroidogenic proteins were found only in inner membrane fractions which were shown to contain cytochrome P-450 C27 side-chain cleavage and P-450 11 beta-hydroxylase together with adrenodoxin and adrenodoxin reductase. Inner membrane catalyzes side-chain cleavage of cholesterol (conversions to pregnenolone) and 11 beta-hydroxylation (DOC----corticosterone) when substrate and NADPH are added. The preparation yields highly purified submitochondrial fractions from Y-1 mouse adrenal tumor cells and from porcine and bovine adrenocortical mitochondria. The method has the virtue of yielding highly purified intermembrane fluid which is not true of other methods for fractionation of adrenal mitochondria. The procedure also yields cleaner preparations of the two membranes than two other published methods currently used to prepare submitochondrial fractions from adrenocortical cells.

Adrenal Glands↗
PubMed1978

Catabolism of threonine in mammals by coupling of L-threonine 3-dehydrogenase with 2-amino-3-oxobutyrate-CoA ligase.

There is doubt about the L-threonine 3-dehydrogenase (EC 1.1.1.103) and threonine aldolase (EC 2.1.2.1) catabolic pathways of L-threonine in mammals which are believed to produce aminoacetone and glycine plus acetaldehyde, respectively. L-Threonine 3-dehydrogenase in disrupted guinea-pig liver mitochondria was investigated in a reaction mixture containing L-threonine without and with CoA and oxaloacetate; L-[U-14C]threonine was included in four similar experiments for autoradiograms. Threonine aldolase was examined in similar mitochondria from liver and kidney. CoA reduced the aminoacetone formed from L-threonine to 10-14% and CoA plus oxaloacetate produced citrate (from CoASAc) in approximately equal amounts to the decrease in aminoacetone. Autoradiograms confirmed the decrease in aminoacetone with the simultaneous appearance of citrate and glycine. No evidence was obtained that threonine aldolase catabolised L-threonine at the concentration used to assay the dehydrogenase. It is concluded that 2-amino-3-oxobutyrate (precursor of aminoacetone), which is produced from L-threonine by L-threonine 3-dehydrogenase, undergoes CoA-dependent cleavage to glycine and CoASAc by 2-amino-3-oxobutyrate-CoA ligase. The results suggest that the coupling of these enzymes provides a new pathway for the catabolism of threonine in mammals.

Acetone↗
PubMed1982

Protein degradation in rat liver. Evidence for populations of protein degradation rates in cellular organelles.

Protein degradation in liver subcellular and submitochondrial fractions from adult rats has been measured by a double isotope technique. Protein subunits have been resolved by two-dimensional polyacrylamide gel electrophoresis. No consistent relationship between subunit size or isoelectric point and degradation rate has been found in any fraction. Frequency analysis of isotope ratios for protein subunits in subcellular and submitochondrial fractions has been carried out. The analyses demonstrate that degradation rates of resolved protein subunits in organelles or organelle subcompartments can be grouped into populations. Resolved protein subunits in subcellular and submitochondrial fractions can be grouped into one, two or three populations. The results suggest limited heterogeneity of protein degradation rates within each subcellular organelle and support the notion that morphological subcompartment rather than molecular property may be the prime determinant of rates of degradation of individual proteins.

Animals↗
PubMed1985

Contribution of different enzymes to flavoprotein fluorescence of isolated rat liver mitochondria.

The fluorescence signal of flavoproteins of rat liver mitochondria was investigated to determine the respective contributions of the various flavoenzymes. About 50% of the overall signal were found to be NAD-linked and caused by alpha-lipoamide dehydrogenase flavin (Em7.4 = -283 mV). Roughly 25% were due to a flavoprotein reducible in a non-NAD-linked reaction. This fluorescent flavoenzyme (Em7.4 = -52 mV) has been tentatively identified as a flavoprotein of the fatty-acid-oxidizing system, most probably the electron transfer flavoprotein. The remaining 25% of the signal are accounted for by flavoenzymes which are reducible by dithionite only. These flavoenzymes were not involved in the flavoprotein fluorescence alterations accompanying changes in electron flow through the respiratory chain. Contributions of other mitochondrial flavoproteins such as succinate dehydrogenase, NADH dehydrogenase, alpha-glycerophosphate dehydrogenase, proline dehydrogenase, and choline oxidase, to the overall flavin fluorescence signal of isolated rat liver mitochondria can be neglected.

Animals↗
PubMed1989

Isolation of glyoxalase II from two different compartments of rat liver mitochondria. Kinetic and immunochemical characterization of the enzymes.

Two separate pools of glyoxalase II were demonstrated in rat liver mitochondria, one in the intermembrane space and the other in the matrix. The enzyme was purified from both sources by affinity chromatography on S-(carbobenzoxy)glutathione-Affi-Gel 40. From both crude and purified preparations polyacrylamide gel-electrophoresis resolved multiple forms of glyoxalase II, two from the intermembrane space and five from the matrix. Among the thioesters of glutathione tested as substrates, S-D-lactoylglutathione was hydrolyzed most efficiently by the enzymes from both sources. Significant differences were observed in the specificities between the intermembrane space and matrix enzymes with S-acetoacetylglutathione, S-acetylglutathione, S-propionylglutathione and S-succinylglutathione as substrates. Pure glyoxalase II from rat liver cytosol was chemically polymerized and used as antigen. Antibodies were raised in rabbits and the antiserum was used for comparison of the two purified mitochondrial enzymes with cytosolic glyoxalase II by immunoblotting. The enzyme purified from the intermembrane space cross-reacted with the antiserum, but the matrix glyoxalase II did not. The results give evidence for the presence in rat liver mitochondria of two species of glyoxalase II with differing characteristics. Only the enzyme from the intermembrane space appears to resemble the cytosolic glyoxalase II forms.

Animals↗
PubMed1981

The transport of cations in mitochondria.

The present paper has reviewed several factors related to ion transport and examined the properties of cation transport in mitochondria. The analysis suggests that: (1) The concept that a metabolically dependent electrical potential across the mitochondrial membrane plays a role in determining ion fluxes and steady-state concentrations is not justified and the data indicate that such exchanges are generally electroneutral. (2) Generally, the influx and efflux of an ion proceed by the same mechanism with at least one exception. (3) There are indications that some of the steps in transport are common to several cations. (4) The idea that carrier or ionophoric molecules are involved in cation transport has been examined in some detail together with the possible involvement of some known mitochondrial components. In particular, a model has been introduced in which local charge imbalances produced by H+ fluxes serve as the driving force of transport. The molecules of the complex are arranged in series in a tripartite arrangement including a filter or gate, a nonselective channel and an H+-transferring portion linked to either electron transport or the ATPase. Parts of this model have been introduced by other investigators. Models in which different portions of channels have differing functions have been proposed previously for other transport systems.

Animals↗