scholarly journals Energy-conserving reactions in phosphorylating electron-transport particles from Nitrobacter winogradskyi. Activation of nitrite oxidation by the electrical component of the protonmotive force

1976 ◽  
Vol 156 (3) ◽  
pp. 481-491 ◽  
Author(s):  
J G Cobley
Keyword(s):  
Electron Transport ◽  
Reaction Medium ◽  
Respiratory Control ◽  
Nadh Oxidation ◽  
Protonmotive Force ◽  
Maximal Effect ◽  
Carbonyl Cyanide ◽  
Electrical Component ◽  
Stimulation Of ◽  
No2 Oxidation

1. In electron-transport particles (ET particles) prepared from Nitrobacter winogradskyi, the uncoupling agent carbonyl cyanide phenylhydrazone increased the rate of NADH oxidation but decreased the rate of oxidation of NO2-. Its effectiveness in stimulating NADH oxidation closely paralleled its effectiveness in inhibiting NO2- oxidation. 2. In the presence of ADP and phosphate the oxidation of NADH was stimulated, whereas the oxidation of NO2- was inhibited. In the presence of excess of Pi the concentration dependence with respect to ADP was the same for acceleration of NADH oxidation and inhibition of NO2- oxidation. 3. Oligomycin inhibited NADH oxidation and stimulated the oxidation of NO2-. The concentration of oligomycin required to produce half-maximal effect in both systems was the same. 4. The apparent Km for NO2- was not affected by ADP together with Pi, by uncoupling agent or by oligomycin. 5. With NADH as substrate, classical respiratory control was observed. With NO2- as substrate the respiratory-control ratio was less than unity. 6. A reversible uptake of H+ accompanied the oxidation of NO2- by ET particles. 7. In the presence of NH4Cl or cyclohexylamine hydrochloride, H+ uptake was abolished and increased rates of NO2- oxidation were observed. When valinomycin was present in the reaction medium, low concentrations of NH4Cl inhibited NO2- oxidation. 8. Pretreatment of ET particles with oligomycin enhanced the stimulation of NO2- oxidation induced by NH4Cl or by cyclohexylamine hydrochloride. Pretreatment with the uncoupler carbonyl cyanide phenylhydrazone prevented these stimulations. 9. In the presence of dianemycin together with K+, the uptake of H+ was abolished and the rate of NO2- oxidation was increased. In contrast, in the presence of valinomycin together with K+, the uptake of H+ was increased, and the rate of NO2- oxidation decreased. 10. Sodium tetraphenylboron was found to be an inhibitor of NO2- oxidation, but caused a stimulation of NADH oxidation which was dependent on the presence of NH4Cl or cyclohexylamine hydrochloride. 11. It is concluded that the enhanced rate of NO2- oxidation observed in the absence of energy-dissipating processes clearly relates to some state before the involvement of adenine nucleotides, and it is suggested that the oxidation of NO2- generates a protonmotive force, the electrical component of which controls the rate of NO2- oxidation.

scholarly journals Reduction of cytochromes by nitrite in electron-transport particles from Nitrobacter winogradskyi: proposal of a mechanism for H+ translocation

1976 ◽  
Vol 156 (3) ◽  
pp. 493-498 ◽  
Author(s):  
J G Cobley
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Respiratory Chain ◽  
Single Electron ◽  
Reduced Form ◽  
Protonmotive Force ◽  
Carbonyl Cyanide ◽  
Cytochromes C ◽  
Electrical Component ◽  
No2 Oxidation

1. A novel component in the respiratory chain of Nitrobacter winogradskyi was identified. This component absorbs maximally at 552.5 nm when in its reduced form, has an Eo' (pH7.0) value of-110mV and undergoes reduction by a mechanism involving the transfer of a single electron. 2. Degrees of reduction of cytochromes c and a1 in electron-transport (ET) particles were monitored during the course of NO2- oxidation, and the effects of ADP together with Pi, oligomycin and of carbonyl cyanide phenylhydrazone were determined. 3. The influences of ionophorous antibiotics, NH4Cl and cyclohexylamine hydrochloride on the reductions of cytochromes c and a1 by NO2- indicate that the flow of reducing equivalents from cytochrome a1 (+350mV) to cytochrome c (+270mV) is facilitated by deltapsi, the electrical component of the protonmotive force. 4. Cytochromes c and a1 in ET particles are reduced by the non-physiological reductant KBH4 in a manner similar to that observed with the physiological reductant NO2-. 5. To account both for the observed cytochrome reductions and for the translocation of H+ ions which accompanies NO2- oxidation, a mechanism is proposed which involves the transfer of a hydride equivalent (H+ plus 2e) inward across the membrane of the ET particle in response to deltapsi.

scholarly journals The effect of chloroform on mitochondrial energy transduction

1996 ◽  
Vol 320 (3) ◽  
pp. 837-845 ◽  
Author(s):  
Lee-Feng CHIEN ◽  
Martin D. BRAND
Keyword(s):  
Electron Transport ◽  
Atp Hydrolysis ◽  
Electron Flow ◽  
Protonmotive Force ◽  
Rate Dependent ◽  
Carbonyl Cyanide ◽  
Apparent Decrease ◽  
Electron Transport Complexes ◽  
The Relationship ◽  
Flow Pathway

The effect of chloroform on mitochondrial respiration with succinate was investigated by applying the method of Brand, Chien and Diolez [(1994) Biochem. J. 297, 27–29] to examine whether chloroform causes redox slip (fewer protons pumped per electron transferred) during mitochondrial electron transport. N,N,N´,N´-Tetramethyl-p-phenylenediamine (TMPD), which lowers H+/O (the number of protons pumped to the external medium by the electron transport complexes per oxygen atom consumed) by altering the electron flow pathway, was investigated for comparison. Non-phosphorylating mitochondria that had been treated with 350 µM TMPD or 30 mM chloroform were titrated with malonate in the presence of submaximal concentrations of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). Linear relations between CCCP-induced extra respiration and protonmotive force were obtained. These results showed that there was no measurable protonmotive force-dependent or rate-dependent slip in mitochondria treated with either TMPD or chloroform. However, both TMPD and chloroform seemed to decrease H+/O in a manner independent of protonmotive force and rate. The relationship between non-phosphorylating respiration and protonmotive force was simulated in mitochondria of which 25% of the total population were assumed to have been broken. The simulation showed that the apparent decrease in H+/O on the addition of TMPD or chloroform to mitochondria could be in principle accounted for by breakage. Assays of mitochondrial breakage (ATP hydrolysis in the presence of atractyloside and oxidation of exogenous NADH) showed that chloroform broke mitochondria but TMPD did not. We conclude that chloroform changes the measured H+/O as an artifact by causing mitochondrial breakage and does not cause measurable redox slip, whereas TMPD genuinely lowers H+/O.

scholarly journals Studies on the Energy Metabolism of Human Leukocytes

Blood ◽  
1967 ◽  
Vol 30 (2) ◽  
pp. 168-175 ◽  
Author(s):  
JOHN M. FOSTER ◽  
MARY L. TERRY ◽  
Harriet Gunther
Keyword(s):  
Energy Metabolism ◽  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Respiratory Control ◽  
Endogenous Respiration ◽  
Mitochondrial Oxidative Phosphorylation ◽  
Human Leukocytes ◽  
Endogenous Activity ◽  
Stimulation Of

Abstract 1. Oxidative phosphorylation has been studied in mitochondrial preparations from human leukocytes, using recently developed methods for homogenization, measuring respiration, and assaying for ATP. 2. Appreciable stimulation of both respiration and phosphorylation was limited to 3 substrates: succinate, malate, and α-glycerophosphate. The effects of other substrates were minimal. 3. The stimulating effects of these 3 substrates responded to inhibitors in a manner typical of mitochondrial oxidative phosphorylation. There was also considerable endogenous activity which, however, was insensitive to inhibitors. It is concluded the endogenous respiration and phosphorylation are not associated with electron transport. Subtracting their values from the data, P/O ratios consistent with good phosphorylation with the 3 substrates are obtained. 4. Studies with oligomycin and dinitrophenol suggest the presence of respiratory control. This indicates the mitochondria are intact. It is concluded that in the intact leukocyte the mitochondria are a major source of ATP.

scholarly journals Mechanism of stimulation of endogenous fermentation in yeast by carbonyl cyanide m-chlorophenylhydrazone.

1987 ◽  
Vol 262 (29) ◽  
pp. 14154-14157
Author(s):  
A Noshiro ◽  
C Purwin ◽  
M Laux ◽  
K Nicolay ◽  
W A Scheffers ◽  
...  
Keyword(s):  
Carbonyl Cyanide ◽  
Stimulation Of

Effect of Magnesium and Calcium Ions on the Photoelectron Transport Activity of Low-Salt Suspended Hydrilla verticillata Thylakoids: Possible Sites of Cation Interaction

1998 ◽  
Vol 53 (9-10) ◽  
pp. 849-856
Author(s):  
Sujata R. Mishra ◽  
Surendra Chandra Sabat
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Donor ◽  
Water Oxidation ◽  
Electron Flow ◽  
Hydrilla Verticillata ◽  
Transport Activity ◽  
Low Salt ◽  
Electron Transport Activity ◽  
Stimulation Of

Stimulatory effect of divalent cations like calcium (Ca2+) and magnesium (Mg2+) was investigated on electron transport activity of divalent cation deficient low-salt suspended (LS) thylakoid preparation from a submerged aquatic angiosperm, Hydrilla verticillata. Both the cations stimulated electron transport activity of LS-suspended thylakoids having an intact water oxidation complex. But in hydroxylamine (NH2OH) - or alkaline Tris - washed thylakoid preparations (with the water oxidation enzyme impaired), only Ca2+ dependent stimulation of electron transport activity was found. The apparent Km of Ca2+ dependent stimulation of electron flow from H2O (endogenous) or from artificial electron donor (exogenous) to dichlorophenol indophenol (acceptor) was found to be identical. Calcium supported stimulation of electron transport activity in NH2OH - or Tris - washed thylakoids was electron donor selective, i.e., Ca2+ ion was only effective in electron flow with diphenylcarbazide but not with NH2OH as electron donor to photosystem II. A magnesium effect was observed in thylakoids having an intact water oxidation complex and the ion became unacceptable in NH2OH - or Tris - washed thylakoids. Indirect experimental evidences have been presented to suggest that Mg2+ interacts with the water oxidation complex, while the Ca2+ interaction is localized betw een Yz and reaction center of photosystem II.

scholarly journals Thermodynamic control of electron flux through mitochondrial cytochrome bc1 complex

1985 ◽  
Vol 225 (2) ◽  
pp. 399-405 ◽  
Author(s):  
G C Brown ◽  
M D Brand
Keyword(s):  
Liver Mitochondria ◽  
Cytochrome Bc1 ◽  
Rat Liver Mitochondria ◽  
Protonmotive Force ◽  
Bc1 Complex ◽  
Thermodynamic Control ◽  
Cytochrome Bc1 Complex ◽  
Redox States ◽  
Force Ratio ◽  
Carbonyl Cyanide

The redox states of exogenously added ubiquinone-2 and cytochrome c, and the protonmotive force (delta p) of rat liver mitochondria were measured as the respiration rate was titrated with the uncoupler carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone. The force ratio delta Eh/delta p across the bc1 complex was close to 1:1 in State 4, indicating an H+/e- stoichiometry of 1:1 for the cytochrome bc1 complex, excluding protons moved by pool ubiquinone. Assuming a constant stoichiometry the rate of electron transport increased linearly with the disequilibrium (delta Eh - delta p) across the complex.

scholarly journals Senescence-associated changes in respiration and oxidative phosphorylation in primary human fibroblasts

2004 ◽  
Vol 380 (3) ◽  
pp. 919-928 ◽  
Author(s):  
Eveline HUTTER ◽  
Kathrin RENNER ◽  
Gerald PFISTER ◽  
Petra STÖCKL ◽  
Pidder JANSEN-DÜRR ◽  
...  
Keyword(s):  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Replicative Senescence ◽  
Citrate Synthase ◽  
Human Fibroblasts ◽  
Respiratory Control ◽  
Compensatory Mechanisms ◽  
Intact Cells ◽  
Atp Production ◽  
Human Diploid Fibroblasts

Limitation of lifespan in replicative senescence is related to oxidative stress, which is probably both the cause and consequence of impaired mitochondrial respiratory function. The respiration of senescent human diploid fibroblasts was analysed by highresolution respirometry. To rule out cell-cycle effects, proliferating and growth-arrested young fibroblasts were used as controls. Uncoupled respiration, as normalized to citrate synthase activity, remained unchanged, reflecting a constant capacity of the respiratory chain. Oligomycin-inhibited respiration, however, was significantly increased in mitochondria of senescent cells, indicating a lower coupling of electron transport with phosphorylation. In contrast, growth-arrested young fibroblasts exhibited a higher coupling state compared with proliferating controls. In intact cells, partial uncoupling may lead to either decreased oxidative ATP production or a compensatory increase in routine respiration. To distinguish between these alternatives, we subtracted oligomycin-inhibited respiration from routine respiration, which allowed us to determine the part of respiratory activity coupled with ATP production. Despite substantial differences in the respiratory control ratio, ranging from 4 to 11 in the different experimental groups, a fixed proportion of respiratory capacity was maintained for coupled oxidative phosphorylation in all the experimental groups. This finding indicates that the senescent cells fully compensate for increased proton leakage by enhanced electron-transport activity in the routine state. These results provide a new insight into age-associated defects in mitochondrial function and compensatory mechanisms in intact cells.

OCTOPAMINERGIC MODULATION OF THE FOREWING STRETCH RECEPTOR IN THE LOCUST LOCUSTA MIGRATORIA

1990 ◽  
Vol 149 (1) ◽  
pp. 255-279 ◽  
Author(s):  
JAN-MARINO RAMIREZ ◽  
IAN ORCHARD
Keyword(s):  
Intact Animal ◽  
Locusta Migratoria ◽  
Beat Frequency ◽  
Motor Pattern ◽  
Stretch Receptor ◽  
Maximal Effect ◽  
Naturally Occurring ◽  
Entire Central Nervous System ◽  
Dorsal Unpaired Median ◽  
Stimulation Of

Modulatory actions of various biogenic amines and peptides on the locust forewing stretch receptor (SR) were examined. The response of the SR to sinusoidal wing movements was unaffected by physiological concentrations (5×10−8moll−1) of the peptides AKHI, AKHII, proctolin and FMRFamide. The biogenic amine octopamine, however, enhanced the SR response in a dosedependent manner when injected into the haemolymph of an almost intact animal or perfused over an isolated thorax preparation in which head, abdomen, gut and the entire central nervous system were removed (threshold at 5×10−8moll−1, maximal effect at 5×10−4moH−1 DL-octopamine). The SR was as sensitive to D-octopamine, the naturally occurring isomer of octopamine, as it was to DLoctopamine. Serotonin was equal to octopamine in effectiveness, followed in order of potency by synephrine, metanephrine and tyramine. Dopamine was ineffective. Phentolamine, but not DL-propranolol, antagonized the action of octopamine. The threshold of the modulatory effect of octopamine on the SR suggests that the increased haemolymph octopamine level which occurs during flight is sufficient to increase the SR activity. Two observations suggest that dorsal unpaired median (DUM) cells are involved in the octopaminergic modulation of the SR during flight: (1) selective stimulation of these cells modulated the SR response and this effect was blocked by phentolamine; and (2) a number of DUM cells were activated during flight. These results suggest that the SR activity is enhanced by octopamine following the onset of flight. Since the SR is involved in the control of wing beat frequency, the modulation of the SR might influence the generation of the motor pattern in flying locusts.

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