scholarly journals The pathway of electron flow through ubiquinol:cytochrome c oxidoreductase in the respiratory chain Evidence from inhibition studies for a modified ‘Q cycle’

1982 ◽  
Vol 206 (3) ◽  
pp. 679-679
Keyword(s):  
Respiratory Chain ◽  
Electron Flow ◽  
Q Cycle ◽  
Flow Through ◽  
Inhibition Studies

scholarly journals The pathway of electron flow through ubiquinol:cytochrome c oxidoreductase in the respiratory chain. Evidence from inhibition studies for a modified ‘Q cycle’

1982 ◽  
Vol 204 (1) ◽  
pp. 49-59 ◽  
Author(s):  
A P Halestrap
Keyword(s):  
Mitochondrial Membrane ◽  
Electron Flow ◽  
Reduced Form ◽  
Protonmotive Force ◽  
Reverse Effect ◽  
Aerobic Conditions ◽  
Q Cycle ◽  
Cytochromes C ◽  
Flow Through ◽  
Inhibition Studies

1. Cytochrome spectra of the liver and heart mitochondria incubated under various conditions are presented to compare the effects of antimycin, colletotrichin and 2-heptyl-4-hydroxyquinoline N-oxide (HQNO) additions. 2. Under aerobic conditions, in State 4, in the presence of uncoupler or in the presence of cyanide, all three inhibitors caused oxidation of cytochromes c and c1, but different changes in the spectra of the b cytochromes. Antimycin caused oxidation of a peak at 558 nm and reduction of peaks at 562 nm and 566 nm, whereas colletotrichin caused reduction of peaks at 558 nm and 566 nm and oxidation at 562 nm. HQNO had an effect on the spectra intermediate between those of the two other inhibitors. 3. Under aerobic conditions in the presence of 5 mM-succinate and 5 mM-fumarate, antimycin caused reduction of a peak at 566 nm and oxidation of a peak at 558 nm, whereas colletotrichin had the reverse effect and HQNO caused reduction of a peak at 562 nm. 4. Colletotrichin inhibition of the ADP-stimulated oxidation of glutamate + malate was enhanced by succinate addition and declined again with rotenone addition. Similar but smaller effects were seen with inhibition by antimycin and HQNO. 5. Cytochrome spectra are shown of the effects of ADP and uncoupler addition to stimulate respiration progressively. 6. The results are interpreted in terms of a modified ‘Q cycle’ [Mitchell (1976) J. Theor. Biol. 62, 327-367] in which the three inhibitors are postulated to displace ubiquinone and ubisemiquinone specifically bound to cytochromes b on both sides of the membrane. 7. It is suggested that cytochromes b558 and b566 are the same b cytochrome located on the outer surface of the membrane, but binding ubisemiquinone or colletotrichin and ubiquinone or antimycin respectively. Cytochrome b562 is postulated to be on the inner surface of the mitochondrial membrane and to bind either ubiquinone or ubisemiquinone, HQNO would bind to the reduced form of the cytochrome and colletotrichin to the oxidized form. 8. Sites for the locus of action of glucagon and the protonmotive force on electron flow are suggested.

scholarly journals The nature of the stimulation of the respiratory chain of rat liver mitochondria by glucagon pretreatment of animals

1982 ◽  
Vol 204 (1) ◽  
pp. 37-47 ◽  
Author(s):  
A P Halestrap
Keyword(s):  
Respiratory Chain ◽  
Electron Flow ◽  
Liver Mitochondria ◽  
Complex Iii ◽  
Secondary Site ◽  
Rat Liver Mitochondria ◽  
Succinate Oxidation ◽  
Q Cycle ◽  
Cytochromes C ◽  
Stimulation Of

1. Studies on the cytochrome spectra of liver mitochondria from control and glucagon-treated rats in State 4, State 3 and in the presence of uncoupler are reported. 2. The stimulation of electron flow between cytochromes c1 and c observed previously [Halestrap (1978) Biochem. J. 172, 399-405] was shown to be an artefact of Ca2+-induced swelling of mitochondria. 3. When precautions were taken to prevent such swelling, glucagon treatment was shown to enhance the reduction of cytochromes c, c1 and b558 in both State 3 and uncoupled conditions with either succinate or glutamate + malate as substrate. An increase in the reduction of cytochromes b562 and b566 was also seen in some, but not all, experiments. 4. In State 4 with succinate but not glutamate + malate as substrate, cytochromes c, c1, b558, b562 and b566 showed increased reduction. 5. Glucagon stimulated oxidation of duroquinol and palmitoylcarnitine by intact mitochondria and of NADH by disrupted mitochondria. 6. No effect of glucagon on succinate dehydrogenase activity or the temperature-dependence of succinate oxidation could be detected. 7. Glucagon enhanced the inhibition of the respiratory chain by colletotrichin, but not antimycin or 8-heptyl-4-hydroxyquinoline N-oxide. 8. These results are interpreted in terms of a primary stimulation by glucagon of the ‘Q cycle’ [Mitchell (1976) J. Theor. Biol. 62, 827-367] within Complex III (ubiquinol:cytochrome c oxidoreductase) and a secondary site of action involving stimulation of electron flow into Complex III from the ubiquinone pool. 9. Ageing of mitochondria, hyperosmotic treatment or addition of 20 mM-benzyl alcohol opposed the effects of glucagon treatment on cytochrome spectra and colletotrichin inhibition of respiration. 10. These results support the hypothesis that glucagon exerts its effects on the mitochondria by perturbing the membrane structure.

scholarly journals In vitro evidence that phytanic acid compromises Na+,K+-ATPase activity and the electron flow through the respiratory chain in brain cortex from young rats

2010 ◽  
Vol 1352 ◽  
pp. 231-238 ◽  
Author(s):  
Estela Natacha Brandt Busanello ◽  
Carolina Maso Viegas ◽  
Alana Pimentel Moura ◽  
Anelise Miotti Tonin ◽  
Mateus Grings ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Respiratory Chain ◽  
Phytanic Acid ◽  
Brain Cortex ◽  
Electron Flow ◽  
Young Rats ◽  
Flow Through

scholarly journals Inhibition of electron flow through complex I of the mitochondrial respiratory chain of Ehrlich ascites carcinoma cells by methylglyoxal

1994 ◽  
Vol 303 (1) ◽  
pp. 69-72 ◽  
Author(s):  
S Ray ◽  
S Dutta ◽  
J Halder ◽  
M Ray
Keyword(s):  
Oxygen Consumption ◽  
Respiratory Chain ◽  
Complex I ◽  
Electron Flow ◽  
Mitochondrial Respiratory Chain ◽  
Ehrlich Ascites Carcinoma ◽  
Inhibitory Effect ◽  
Ehrlich Ascites ◽  
Flow Through ◽  
Mitochondrial Respiratory

The effect of methylglyoxal on the oxygen consumption of Ehrlich-ascites-carcinoma (EAC)-cell mitochondria was tested by using different respiratory substrates, electron donors at different segments of the mitochondrial respiratory chain and site-specific inhibitors to identify the specific respiratory complex which might be involved in the inhibitory effect of methylglyoxal on the oxygen consumption by these cells. The results indicate that methylglyoxal strongly inhibits ADP-stimulated alpha-oxo-glutarate and malate plus pyruvate-dependent respiration, whereas, at a much higher concentration, methylglyoxal fails to inhibit succinate-dependent respiration. Methylglyoxal also fails to inhibit respiration which is initiated by duroquinol, an artificial electron donor. Moreover, methylglyoxal cannot inhibit oxygen consumption when the NNN'N′-tetramethyl-p-phenylenediamine by-pass is used. The inhibitory effect of methylglyoxal is identical on both ADP-stimulated and uncoupler-stimulated respiration. Lactaldehyde, a catabolite of methylglyoxal, can exert a protective effect on the inhibition of EAC-cell mitochondrial respiration by methylglyoxal. We suggest that methylglyoxal possibly inhibits the electron flow through complex I of the EAC-cell mitochondrial respiratory chain.

Proton translocation coupled to ubiquinol oxidation in Paracoccus denitrificans

1979 ◽  
Vol 57 (2) ◽  
pp. 172-177 ◽  
Author(s):  
Hugh G. Lawford
Keyword(s):  
Respiratory Chain ◽  
Oxidase Activity ◽  
Paracoccus Denitrificans ◽  
Electron Flow ◽  
Proton Translocation ◽  
Energy Coupling ◽  
Ubiquinol Oxidase ◽  
Transport Chain ◽  
Flow Through ◽  
Chemiosmotic Coupling

Measurements were made of the stoichiometry of proton translocation associated with electron flow through the cytochrome-dependent region of the aerobically induced respiratory chain of Paracoccus denitrificans using the pulse oxidant method and rotenone to inhibit NADH dehydrogenase activity. Paracoccus denitrificans (ATCC 13543) was grown aerobically in carbon-limited continuous culture D = 0.27 h−1D, dilution rate per hour) with succinate as sole carbon and energy source. Oxidation of exogenous ubiquinol1 by starved cells was significantly accelerated by treatment of the cells with lysozyme. Spectrophotometric assay of ubiquinol1 oxidase activity in rotenone-poisoned spheroplasts revealed an apparent Km of 25 μM and a Vmax of 217 nmol/min per milligram protein. In site 1 poisoned spheroplasts proton translocation was dependent on the presence of added respiratory substrate, either succinate or ubiquinol1, where the observed ratios of protons ejected from the membrane per atom of oxygen consumed (← H+: O) were 5.3 and 5.2 respectively. The rate of proton translocation associated with succinate and ubiquinol1 oxidation was significantly decreased in the presence of antimycin A and completely abolished with cyanide. Net proton translocation was not observed after the addition of uncoupler (CCCP). Assuming there are two potential sites of energy conservation associated with the region of the respiratory chain from ubiquinone to cytochrome oxidase (i.e., ubiquinol oxidase activity), then the number of protons ejected during the transfer of one pair of reducing equivalents along a region of the electron transport chain equivalent to a single energy-coupling or conservation site (← H+: site) ratio in P. denitrificans is closer to 3 than 2 as predicted by Mitchell's chemiosmotic coupling hypothesis.

Mitochondrial function in flying honeybees (Apis mellifera): respiratory chain enzymes and electron flow from complex III to oxygen

2000 ◽  
Vol 203 (5) ◽  
pp. 905-911 ◽  
Author(s):  
R.K. Suarez ◽  
J.F. Staples ◽  
J.R. Lighton ◽  
O. Mathieu-Costello
Keyword(s):  
Surface Area ◽  
Muscle Mass ◽  
Respiratory Chain ◽  
Mitochondrial Function ◽  
Electron Flow ◽  
Complex Iii ◽  
High Mass ◽  
Metabolic Rates ◽  
Turnover Rates ◽  
Respiratory Enzymes

The biochemical bases for the high mass-specific metabolic rates of flying insects remain poorly understood. To gain insights into mitochondrial function during flight, metabolic rates of individual flying honeybees were measured using respirometry, and their thoracic muscles were fixed for electron microscopy. Mitochondrial volume densities and cristae surface densities, combined with biochemical data concerning cytochrome content per unit mass, were used to estimate respiratory chain enzyme densities per unit cristae surface area. Despite the high content of respiratory enzymes per unit muscle mass, these are accommodated by abundant mitochondria and high cristae surface densities such that enzyme densities per unit cristae surface area are similar to those found in mammalian muscle and liver. These results support the idea that a unit area of mitochondrial inner membrane constitutes an invariant structural unit. Rates of O(2) consumption per unit cristae surface area are much higher than those estimated in mammals as a consequence of higher enzyme turnover rates (electron transfer rates per enzyme molecule) during flight. Cytochrome c oxidase, in particular, operates close to its maximum catalytic capacity (k(cat)). Thus, high flux rates are achieved via (i) high respiratory enzyme content per unit muscle mass and (ii) the operation of these enzymes at high fractional velocities.

scholarly journals The C Termini of Constitutive Nitric-oxide Synthases Control Electron Flow through the Flavin and Heme Domains and Affect Modulation by Calmodulin

2000 ◽  
Vol 275 (38) ◽  
pp. 29225-29232 ◽  
Author(s):  
Linda J. Roman ◽  
Pavel Martásek ◽  
R. Timothy Miller ◽  
Dawn E. Harris ◽  
Melissa A. de la Garza ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Electron Flow ◽  
Nitric Oxide Synthases ◽  
Flow Through

Electron Flow through Geometrical Discontinuity in Coaxial Magnetically Insulated Transmission Lines

2000 ◽  
Vol 39 (Part 1, No. 9A) ◽  
pp. 5280-5286 ◽  
Author(s):  
Kazuki Hiraoka ◽  
Mitsuo Nakajima ◽  
Makoto Shiho ◽  
Kazuhiko Horioka
Keyword(s):  
Transmission Lines ◽  
Electron Flow ◽  
Flow Through ◽  
Geometrical Discontinuity

SINGLE ELECTRON DEVICES

1998 ◽  
Vol 09 (01) ◽  
pp. 165-207 ◽  
Author(s):  
DORAN D. SMITH
Keyword(s):  
Tunnel Junctions ◽  
Electron Flow ◽  
Superconducting Devices ◽  
Time Correlation ◽  
Single Electron ◽  
Net Charge ◽  
Flow Through ◽  
Single Electron Devices ◽  
Electron Devices ◽  
Electron Effects

In the mid 1980s Averin and Likharev predicted that with the use of ultrasmall tunnel junctions a time correlation of electron flow through a junction could be observed, and permit the measurement of the effect of a net charge of less than one electron on the junction. Both effects were soon experimentally verified, and since that time there has been an explosion of work in the filed of single electron devices. This chapter reviews the fundamental concepts behind the operation of such devices. it then describes some of the single electron effects studied in semiconductors. Superconducting devices are then constrasted to the semiconductor and the normal metal single electron devices. The details of some current applications are described, and a thumbnail sketch of current fabrication methods is given.

scholarly journals Correction to Electron Flow through Metalloproteins

2016 ◽  
Vol 116 (14) ◽  
pp. 8313-8313
Author(s):  
Jay R. Winkler ◽  
Harry B. Gray
Keyword(s):  
Electron Flow ◽  
Flow Through
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