SEARCH · PubMed Health

Results for “Submitochondrial Particles”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 19 recordsLinked to original sources

PubMed1975

Synthesis of adenosine triphosphate by an artificially imposed electrochemical proton gradient in bovine heart submitochondrial particles.

Submitochondrial particles subjected to an artificially imposed electrochemical proton gradient consisting of a pH gradient (acid to base transition) and membrane potential (low to high K-+ transition in the presence of valinomycin) catalyzed the net synthesis of 2.5 nmol of [-32P]ATP per mg of protein from ADP and 32-Pi. Optimal reaction conditions included incubation of submitochondrial particles in malonate at pH 5.0 with valinomycin in the absence of added K-+, followed by a rapid transition to pH 7.5 and 100 mM K-+. ATP synthesis continued for about 6 s and was sensitive to uncouplers or oligomycin but insensitive to inhibitors of electron transport. Lower amounts of ATP were formed by either the pH gradient (25%) of K-+ gradient (15%) alone. These results demonstrate that an electrochemical gradient of protons can drive the synthesis of ATP by reversal of the proton-translocating ATPase independent of electron transport.

Adenosine Triphosphatases↗

PubMed1976

Removal of "tightly bound" nucleotides from phosphorylating submitochondrial particles.

Phosphorylating submitochondrial particles from beef heart (ETPH) prepared here contained about 2.4 nmol of ATP and 1.9 nmol of ADP/mg of protein after repeated washing of the particles. Essentially all of the "tightly bound " ATP and ADP was removed by trypsin treatment. The trypsin-treated ETPH had increased ATPase activity, undiminished NADH oxidase and succinate oxidase activity, but energy-coupling activity (ATP-driven reversed electron transfer) was abolished. Removal of half the ATP and ADP occurred at low levels of trypsin and was associated with loss of half of the coupling activity. Gel filtration of ETPH in high ionic strength buffer also removed ADP and ATP from the particles, resulting in loss of energy-coupling activity, while ATPase activity was increased. The results support the contention that the tightly bound ADP is essential in energy coupling in mitochondria. Tightly bound ATP may also play an essential role.

Adenosine Diphosphate↗

PubMed1976

Anion and amine uptake and uncoupling in submitochondrial particles.

1. Unlike chloroplasts, submitochondrial particles are not uncoupled by nigericin + KCl or NH4Cl. Also the uncoupling effect of lipophilic anions is largely independent of the addition of weak bases. 2. Low concentrations of permeant anions cause a shift of the steady-state energy level rather than a cycle of energy utilization. The degree of inhibition of ATP synthesis by tetraphenylboron is larger than required for the uptake of the anion. 3. Lipophilic anions such as bromthymolblue, bromcresolpurple, and 8-anilino-1-napthalene sulphonate cause a pH-independent, 50% uncoupling in submitochondrial particles at concentrations of 3, 30 and 30 muM, respectively. The passive interaction of bromthymolblue and bromcresolpurple appears as a pH-dependent distribution between two pHases. ATP causes a pH-independent slight shift in the anion distribution, with negligible anion accumulation. 4. Addition of amines to energized submitochondrial particles results in two types of effects; uptake of amines and uncoupling. While in chloroplasts amine uptake and uncoupling are closely associated, this is not the case in submitochondrial particles. The uncoupling effect is observed only with lipophilic and not with hydrophilic amines, and the degree of uncoupling increases with the lipophilicity of the amines. The amine uptake, on the other hand, is accompanied by negligible uncoupling. 5. While the uptake of amines is dependent on the presence of non-permeant anions, such as Cl-, the uncoupling effect is independent of Cl-. Furthermore the amine uncoupling is markedly enhanced by lipophilic anions. 6. The view is discussed that the uncoupling effect of lipophilic anions and lipophilic amines in submitochondrial particles is due to a catalytic energy dissipation rather than to a stoichiometry energy utilization. The molecular mechanism of uncoupling presumably involves a cycling of charges after a perturbation of the membrane structure.

Amines↗

PubMed1979

Characterization of cyanide-insensitive respiration in mitochondria and submitochondrial particles of Moniliella tomentosa.

Mitochondria and submitochondrial particles of the osmophilic yeast-like fungus Moniliella tomentosa may respire by means of two pathways: a normal cytochrome pathway, sensitive to cyanide and antimycin A, and an alternative pathway, which is insensitive to these inhibitors but is specifically inhibited by salicylhydroxamic acid. The affinities of both oxidases for succinate and NADH as substrates, for O(2) as terminal electron acceptor, and for AMP as stimulator of the alternative oxidase were determined. 1. Submitochondrial particles of M. tomentosa may also respire by means of a cyanide-sensitive and/or cyanide-insensitive system. 2. The activities of both oxidases as compared with the total activity are roughly the same in submitochondrial particles as in the original mitochondria. 3. The terminal oxidase of the cyanide-insensitive pathway requires a 10-fold higher O(2) concentration for saturation than does cytochrome c oxidase. 4. The apparent K(m) for succinate is about 3 times higher for the alternative than for the normal oxidase when measured in mitochondria, and 4-10 times higher when measured in submitochondrial particles. The apparent K(m) for NADH is roughly the same for both oxidases. 5. The apparent K(m) values of both oxidases for succinate are always lower in submitochondrial particles than in mitochondria. 6. The apparent K(m) for AMP, acting as a stimulator of the alternative oxidase, is the same (25mum) in mitochondria as in sub-mitochondrial particles. These results are discussed in the light of the structure and localization of the components of the alternative oxidase.

Adenosine Monophosphate↗

PubMed1977

Mitochondrial respiratory chain of Tetrahymena pyriformis: the properties of submitochondrial particles and the soluble b and c type pigments.

Submitochondrial particles isolated from Tetrahymena pyriformis contain essentially the same redox carriers as those present in parental mitochondria: at pH 7.2 and 22 degree C there are two b-type pigments with half-reduction potentials of --0.04 and --0.17 V, a c-type cytochrome with a half reduction potential of 0.215 V, and a two-component cytochrome a2 with Em7.2 of 0.245 and 0.345 V. EPR spectra of the aerobic submitochondrial particles in the absence of substrate show the presence of low spine ferric hemes with g values at 3.4 and 3.0, a high spin ferric heme with g =6, and a g=2.0 signal characteristic of oxidized copper. In the reduced submitochondrial particles signals of various iron-sulfur centers are observed. Cytochrome c553 is lost from mitochondria during preparation of the submitochondrial particles. The partially purified cytochrome c553 is a negatively charged protein at neutral pH with an Em7.2 of 0.25 V which binds to the cytochrome c-depleted Tetrahymena mitochondria in the amount of 0.5 nmol/mg protein with KD of 0.8.10(-6) M. Reduced cytochrome c553 serves as an efficient substrate in the reaction with its own oxidase. The EPR spectrum of the partially purified cytochrome c553 shows the presence of a low spin ferric heme with the dominant resonance signal at g=3.28. A pigment with an alpha absorption maximum at 560 nm can be solubilized from the Tetrahymena cells with butanol. This pigments has a molecular weight of approx. 18 000, and Em7.2 of--0.17 V and exhibits a high spin ferric heme signal at g=6.

Cytochrome c Group↗

PubMed1979

Kinetics of the potential-sensitive extrinsic probe oxonol VI in beef heart submitochondrial particles.

The interaction of the potential-sensitive extrinsic probe oxonol VI with beef heart submitochondrial particles has been investigated under time resolved and equilibrium conditions. The time course of the probe absorption spectrum red shift induced by ATP or NADH injection into a suspension of submitochondrial particles in a dye solution is biphasic, consisting of a faster process described by a second-order rate law with k2 approximately 3 x 10(5) M-1 sec-1. For the ATP pulse experiments, the slower process follows first-order kinetics with k1 approximately 0.3 sec-1. In oxygen pulse experiments to an anaerobic dye-particle system, the slower process is not significantly developed due to rapid depletion of the oxygen, but the faster process follows second-order kinetics with the same rate of the oxygen, but the faster process follows second-order kinetics with the same rate constant as for the ATP and NADH cases. Evidence for permeation of the submitochondrial particle membrane by oxonol VI has been obtained; the slower process is interpretable as describing the permeation of the membrane bilayer. The results of the time-resolved work are consistent with a mechanism involving a redistribution of the dye from the bulk phase to the particle membrane. The value of the second-order rate constant for passive binding of the dye to submitochondrial particles is not compatible with a mechanism proposed to explain the microsecond probe response times in bilayer and excitable membrane experiments nor are such rapid signals observed in the oxonol VI-submitochondrial particle system.

Adenosine Triphosphate↗

PubMed1979

[Inhibition of succinate and NADH oxidases of submitochondrial particles by iron chelators and sulfhydryl reagents].

The inhibition of succinate- and NADH-oxidase activities of submitochondrial particles by 4,7-diphenyl-1,10-phenantroline was studied. The inhibition was shown to increase when the particles were pretreated with SH-reagents. The treatment of submitochondrial particles with ethanol in the presence of 1,10-phenantroline resulted in a complete inactivation of succinate oxidase and succinate: tetramethyl-n-phenyldiamine reductase; the succinate PMS reductase activity was only partially inhibited after such treatment. It is concluded that tetramethyl-n-phenyldiamine and phenazine metasulfate react with different sites of the succinate dehydrogenase complex. The changes in the properties of submitochondrial particles after ethanol--phenantroline treatment are apparently due to the effect of non-polar solvent rather than to the extraction of non-haem iron.

Animals↗

PubMed1978

The mechanism of oxidation of reduced nicotinamide dinucleotide phosphate by submitochondrial particles from beef heart.

1. Oxidation of NADPH by various acceptors catalyzed by submitochondrial particles and a partially purified NADH dehydrogenase from beef heart was investigated. Submitochondrial particles devoid of nicotinamide nucleotide transhydrogenase activity catalyze an oxidation of NADPH by oxygen. The partially purified NADH dehydrogenase prepared from these particles catalyzes an oxidation of NADPH by acetylpyridine-NAD. In both cases the rates of oxidation are about two orders of magnitude lower than those obtained with NADH as electron donor. 2. The kinetic characteristics of the NADPH oxidase reaction and reduction of acetylpyridine-NAD by NADPH are similar with regard to pH dependences and affinities for NADPH, indicating that both reactions involve the same binding site for NADPH. The binding of NADPH to this site appears to be rate limiting for the overall reactions. 3. At redox equilibrium NADPH and NADH reduce FMN and iron-sulphur center 1 of NADH dehydrogenase to the same extents. The rate of reduction of FMN by NADPH is at least two orders of magnitude lower than with NADH. 4. It is concluded that NADPH is a substrate of NADH dehydrogenase and that the nicotinamide nucleotide is oxidized by submitochondrial particles via the NADH--binding site of the enzyme.

Animals↗

PubMed1976

Catalytic activity of cytochromes c and c1 in mitochondria and submitochondrial particles.

1. Beef heart mitochondria have a cytochrome c1:c:aa3 ratio of 0.65:1.0:1.0 as isolated; Keilin-Hartree submitochondrial particles ahve a ratio of 0.65:0.4:1.0. More than 50% of the submitochondrial particle membrane is in the 'inverted' configuration, shielding the catalytically active cytochrome c. The 'endogenous' cytochrome c of particles turns over at a maximal rate between 450 and 550 s-1 during the oxidation of succinate or ascorbate plus TMPD; the maximal turnover rate for cytochrome c in mitochondria is 300-400 s-1, at 28 degrees-30 degrees C, pH 7.4. 2. Ascorbate plus N,N,N',N'-tetramethyl-p-phenylene diamine added to antimycin-treated particles induces anomalous absorption increases between 555 and 565 nm during the aerobic steady state, which disappear upon anaerobiosis; succinate addition abolishes this cycle and permits the partial resolution of cytochrome c1 and cytochrome c steady states at 552.5-547 nm and 550-556.5 nm, respectively. 3. Cytochrome c1 is rather more reduced than cytochrome c during the oxidation of succinate and of ascorbate + N,N,N',N'-tetramethyl-p-phenylene diamine in both mitochondria and submitochondrial particles; a near equilibrium condition exists between cytochromes c1 and c in the aerobic steady state, with a rate constant for the c1 leads to c reduction step greater than 10(3) s-1. 4. The greater apparent response of the c/aa3 electron transfer step to salts, the hyperbolic inhibition of succinate oxidation by azide and cyanide, and the kinetic behaviour of the succinate-cytochrome c reductase system, are all explicable in terms of a near-equilibrium condition prevailing at the c1/c step. Endogenous cytochrome c of mitochondria and submitochondrial particles is apparently largely bound to cytochrome aa3 units in situ. Cytochrome c1 can either reduce the cytochrome c-cytochrome aa3 complex directly, or requires only a small extra amount of cytochrome c to carry the full electron transfer flux.

Aerobiosis↗

PubMed1977

Thermodynamics of the electrochemical proton gradient in bovine heart submitochondrial particles.

The electrical and chemical components of the electrochemical proton gradient of submitochondrial particles can be monitored simultaneously by continuously recording optical signals from the probes oxonol-VI and 9-aminoacridine. Either respiration or ATP hydrolysis causes a red shift in the absorption spectrum of oxonol-VI indicative of a membrane potential and a decrease of the fluorescence of 9-aminoacridine indicative of a pH gradient. The magnitude of the membrane potential and pH gradient formed by respiring submitochondrial particles can be modulated by the thermodynamic phosphorylation potential (deltaGp) of the adenine nucleotide system. deltaGp is the Gibbs free energy of ATP synthesis and is defined by the relationship deltaGp = -deltaG'o + RTln([ATP]/[ADP][Pi] where deltaG'o is the standard free energy of ATP hydrolysis. Increasing values of deltaGp cause an increase in the steady state magnitudes of both the membrane potential and pH gradient. Thermodynamic phosphorylation potential titration experiments indicate that the electrochemical proton gradient normally maintained by respiring submitochondrial particles has an energy equivalent to 10.5 to 10.9 kcal/mol.

Adenosine Triphosphate↗

PubMed1978

The use of aurovertin to determine the F1 content of submitochondrial particles and the ATPase complex.

(1) The concentration of aurovertin-binding sites calculated from fluorimetric titrations of submitochondrial particles is equal to the F1 concentration, calculated from the concentration of F1-binding sites in stripped particles. (2) Direct binding experiments show that the fluorescence enhancement of aurovertin bound to submitochondrial particles and the isolated ATPase complex is less (or absent) at higher concentrations than at lower concentrations. The binding data can be described by 'specific' and 'non-specific' binding. The concentration of the 'specific' sites is twice that derived from fluorimetric titrations. (3) After dissociation of the bound F1 with LiCl, fluorimetric titrations with aurovertin yield linear Scatchard plots. The fluorescence enhancement and KD are equal to those of the beta-subunit-aurovertin complex. The concentration of beta-subunits is double the concentration of F1. (4) It is concluded that both for submitochondrial particles and the isolated ATPase complex the most reliable and simple way to determine the F1 content is to dissociate the F1 with LiCl, spin down the insoluble material and titrate the supernatant (containing free beta-subunit) with aurovertin.

Adenosine Triphosphatases↗

PubMed1977

[Proton translocation in membranes of submitochondrial particles].

Effect of an electrophilous inhibitor, chlorophenacyl, on energy-dependent functions of submitochondrial particles is studied. Chlorophenacyl at concentrations up to 1 mM is found practically not to affect the generation of membrane potential under NADH and succinate oxidation and ATP hydrolysis and to be a strong inhibitor of oxidative phosphorylation and reverse electron transport. The mechanism of the inhibition of energy-dependent functions of submitochondrial particles with chlorophenacyl is different from that of electron transport inhibitor, energy transport inhibitors and classical uncoupling agents--protonophors. The data obtained are suggested to be due to the existence of two ways of proton translocation in submitochondrial particle membrane, phosphorylating and non-phosphorylating, the effect of chlorophenacyl being directed on phosphorylating way only.

Biological Transport↗

PubMed1975

Electron-paramagnetic-resonance spectroscopy studies of iron-sulphur centres of submitochondrial particles from iron- and sulphur-deficient. Candida utilis.

1. Measurements were made at 12 degrees K of the electron-paramagnetic-resonance (e.p.r.) spectra of submitochondrial particles from Candida utilis cells grown under conditions that alter the amount of the mitochondrial NADH dehydrogenase (EC 1.6.99.3). 2. Iron-limited growth decreases the extent of iron-sulphur e.p.r. signals to undetectable values that are less than 1 percent of those normally found with glycerol-limited growth. 3. Small but significant signals attributable to the NADH dehydrogenase were detected in submitochondrial particles from sulphate-limited cells. 4. Measurements made on submitochondrial particles prepared from these and other phenotypically modified cells lead us to conclude that the presence of low-temperature e.p.r.-detectable iron-sulphur centres attributable to the NADH dehydrogenase are necessary but not sufficient for the coupling of ATP synthesis to the NADH dehydrogenase reaction in the mitochondrial membrane of C. utilis. 6. The amplitude of the g=2.01 signal observed in non-reduced submitochondrial particles is approximately tenfold diminished by iron limitation but not significantly altered by sulphate limitation.

Adenosine Triphosphate↗

PubMed1979

F1-ATPase from different submitochondrial particles.

1. F1-ATPase has been extracted by the diphosphatidylglycerol procedure from mitochondrial ATPase complexes that differ in ATPase activity, cold stability, ATPase inhibitor and magnesium content. 2. The ATPase activity of the isolated enzymes was dependent upon the activity of the original particles. In this respect, F1-ATPase extracted from submitochondrial particles prepared in ammonia (pH 9.2) and filtered through Sephadex G-50 was comparable to the enzyme purified by conventional procedures (Horstman, L.L. and Racker, E. (1970) J. Biol. Chem. 245, 1336--1344), whereas F1-ATPase extracted from submitochondrial particles prepared in the presence of magnesium and ATP at neutral pH was similar to factor A (Andreoli, T.E., Lam, K.W. and Sanadi, D.R. (1965) J. Biol. Chem. 240, 2644--2653). 3. No systematic relationship has been found in these F1-ATPase preparations between their ATPase inhibitor content and ATPase activity. Rather, a relationship has been observed between this activity and the efficiency of the ATPase inhibitor-F1-ATPase association within the membrane. 4. It is concluded that the ATPase activity of isolated F1-ATPase reflects the properties of original ATPase complex provided a rapid and not denaturing procedure of isolation is employed.

Adenosine Triphosphatases↗

PubMed1975

Beef-heart submitochondrial particles: a mixture of mitochondrial inner and outer membranes.

1. EPR spectra at 9 GHz and 83 degrees K of NADH-reduced anaerobic beef-heart submitochondrial particles, prepared from mitochondria by sonication and centrifugation, contain a signal (gz equals to 2.01, gy equals to 1.94, gx equals to 1.89) due to an iron-sulphur center of the mitochondrial outer membrane. 2. The ratio of inner and outer membranes in submitochondrial particles is not greatly different from that in beef-heart mitochondria. 3. Beef-heart submitochondrial particles free from outer-membrane contamination have been prepared by free-flow electrophoresis. EPR spectra at 83 degrees K of such particles are presented.

Adenosine Triphosphate↗

PubMedDate not supplied

[The effect of oxidazable substrates and ATP on the sensitivity of certain energy-dependent functions submitochondrial particles to phospholipases A, C and D].

The effect of NADH, succinate and ATP on the sensitivity of a number of energy-dependent functions of submitochondrial particles ot phospholipases A, C and D has been studied. It has been shown that in the conditions of oxidation of NADH and succinate by oxygen and also of ATP hydrolysis, the decrease in the phosphorylating activity of the particles under the action of phospholipases C and D accelerates. No such acceleration has been observed with phospholipase A. For other two functions, i. e. reverse electron transfer (ATP-dependent NAD+ reduction by succinate) and ATP-dependent transhydrogenase reaction the results proved to be different. Oxidizable substrates and ATP promoted the maintenance of these functions in the presence of phospholipase A, but did not retard their suppression by phospholipases C and D. The effects of NADH, succinate and ATP on the sensitivity of different energy-dependent functions of submitochondrial particles to phospholipases A, C and D could be removed by the uncoupling agent carbonyl cyanide-m-chlorophenyl hydrazone. The conclusion is made that the effects revealed are associated with an increase in the sensitivity of coupling sites II PAND/OR III to phospholipases C and D and with a decrease in the sensitivity of sites I and IV to phospholipase A on energization of submitochondrial particles.

Adenosine Triphosphate↗

PubMed1976

On the nature of the energised state of submitochondrial particles; investigations with N-aryl naphthalene sulphonate probes.

1. A further investigation has been made of the way in which the fluorescent probes 1-anilino-naphthalene-8-sulphonate and 2-(N-methyl-anilino) naphthalene-6-sulphonate report on the energised state of bovine heart submitochondrial particles. 2. A comparison of the probe responses to energisation with ATP or to a potassium diffusion potential has been made. The fluorescence enhancements seen in these two cases have different characteristics, and in view of this it is questioned whether a substrate generated energised state of a submitochondrial particle can be equated with a trans-membrane potassium diffusion potential. 3. Substitution of ITP for ATP reduces the rate at which either of the probes respond to energisation. In contrast reducing the ATPase activity of the particles by treatment with the covalent ATPase inhibitors 4-chloro-7-nitrobenzofurazan or N,N'-dicyclohexyl-carbodiimide has no effect on this rate. This finding that the rate of the fluorescence changes is directly sensitive to events at the level of the ATPase, but not to the total ATPase activity, suggests that this rate may not be controlled by a delocalised energised state. Reduction of ATPase activity decreases the extent of the fluorescence enhancement and a relationship between the change in probe fluorescence and ATPase activity is given. 4. The results in this paper are discussed in the context of the mechanisms which have been proposed to account for the fluorescence enhancements of N-aryl naphthalene sulphonate probes upon energisation of submitochondrial particles.

Adenosine Triphosphatases↗

PubMed1979

NADH- and NADPH-dependent formation of superoxide anions by bovine heart submitochondrial particles and NADH-ubiquinone reductase preparation.

1. Both NADH and NADPH supported the oxidation of adrenaline to adrenochrome in bovine heart submitochondrial particles. The reaction was completely inhibited in the presence of superoxide dismutase, suggesting that superoxide anions (O(2) (-)) are responsible for the oxidation. The optimal pH of the reaction with NADPH was at pH7.5, whereas that with NADH was at pH9.0. The reaction was inhibited by treatment of the preparation with p-hydroxymercuribenzoate and stimulated by treatment with rotenone. Antimycin A and cyanide stimulated the reaction to the same extent as rotenone. The NADPH-dependent reaction was inhibited by inorganic salts at high concentrations, whereas the NADH-dependent reaction was stimulated. 2. Production of O(2) (-) by NADH-ubiquinone reductase preparation (Complex I) with NADH or NADPH as an electron donor was assayed by measuring the formation of adrenochrome or the reduction of acetylated cytochrome c which does not react with the respiratory-chain components. p-Hydroxymercuribenzoate inhibited the reaction and rotenone stimulated the reaction. The effects of pH and inorganic salts at high concentrations on the NADH- and NADPH-dependent reactions of Complex I were essentially similar to those on the reactions of submitochondrial particles. 3. These findings suggest that a region between a mercurialsensitive site and the rotenone-sensitive site of the respiratory-chain NADH dehydrogenase is largely responsible for the NADH- and NADPH-dependent O(2) (-) production by the mitochondrial inner membranes.

Animals↗