scholarly journals Cytochrome c mediates electron transfer between ubiquinol-cytochrome c reductase and cytochrome c oxidase by free diffusion along the surface of the membrane

1984 ◽  
Vol 217 (2) ◽  
pp. 561-571 ◽  
Author(s):  
R J Froud ◽  
C I Ragan
Keyword(s):  
Phase Transition ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Rotational Diffusion ◽  
Complex Iii ◽  
Complex Iv ◽  
Cytochrome C Reductase ◽  
Ubiquinol Oxidase ◽  
Spin Resonance ◽  
Gel Phase

Ubiquinol oxidase can be reconstituted from ubiquinol-cytochrome c reductase (Complex III) and cytochrome c oxidase (Complex IV) whose endogenous phosphatidylcholine and phosphatidylethanolamine have been replaced by dimyristoylglycerophosphocholine. Phase transition of the lipid has no effect on Complex III and Complex IV activities assayed separately, but ubiquinol oxidase activity rapidly decreases as the temperature is lowered through the phase transition. A spin-labelled yeast cytochrome c derivative has been synthesized. Binding of the cytochrome c to liposomes demonstrates that only cardiolipin is involved under the conditions used for the ubiquinol oxidase experiments. In liposomes consisting of cardiolipin and dimyristoylglycerophosphocholine, e.s.r. (electron-spin-resonance) measurements show that rotational diffusion of cytochrome c is slowed in the gel phase of the latter lipid. We propose that the cytochrome c pool is bound to cardiolipin molecules, whose lateral and rotational diffusion in the bilayer is adequate to account for electron-transport rates.

scholarly journals Cytochrome c-mediated electron transfer between ubiquinol-cytochrome c reductase and cytochrome c oxidase. Kinetic evidence for a mobile cytochrome c pool

1984 ◽  
Vol 217 (2) ◽  
pp. 551-560 ◽  
Author(s):  
R J Froud ◽  
C I Ragan
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
State Level ◽  
Complex Iii ◽  
Molar Ratio ◽  
Cytochrome C Reductase ◽  
Molar Ratios ◽  
Ubiquinol Oxidase ◽  
Mediated Electron Transfer ◽  
Pool Model

Ubiquinol oxidase has been reconstituted from ubiquinol-cytochrome c reductase (Complex III), cytochrome c and cytochrome c oxidase (Complex IV). The steady-state level of reduction of cytochrome c by ubiquinol-2 varies with the molar ratios of the complexes and with the presence of antimycin in a way that can be quantitatively accounted for by a model in which cytochrome c acts as a freely diffusible pool on the membrane. This model was based on that of Kröger & Klingenberg [(1973) Eur. J. Biochem. 34, 358-368] for ubiquinone-pool behaviour. Further confirmation of the pool model was provided by analysis of ubiquinol oxidase activity as a function of the molar ratio of the complexes and prediction of the degree of inhibition by antimycin.

scholarly journals Properties of ubiquinol oxidase reconstituted from ubiquinol-cytochrome c reductase, cytochrome c and cytochrome c oxidase

1982 ◽  
Vol 202 (2) ◽  
pp. 527-534 ◽  
Author(s):  
R J Diggens ◽  
C I Ragan
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Oxidase Activity ◽  
Maximal Activity ◽  
Complex Iii ◽  
Protein Ratio ◽  
Quinol Oxidase ◽  
Cytochrome C Reductase ◽  
Ubiquinol Oxidase ◽  
High Affinity

Ubiquinol-cytochrome c reductase (Complex III), cytochrome c and cytochrome c oxidase can be combined to reconstitute antimycin-sensitive ubiquinol oxidase activity. In 25 mM-acetate/Tris, pH 7.8, cytochrome c binds at high-affinity sites (KD = 0.1 microM) and low-affinity sites (KD approx. 10 microM). Quinol oxidase activity is 50% of maximal activity when cytochrome c is bound to only 25% of the high affinity sites. The other 50% of activity seems to be due to cytochrome c bound at low-affinity sites. Reconstitution in the presence of soya-bean phospholipids prevents aggregation of cytochrome c oxidase and gives rise to much higher rates of quinol oxidase. The cytochrome c dependence was unaltered. Antimycin curves have the same shape regardless of lipid/protein ratio, Complex III/cytochrome c oxidase ratio or cytochrome c concentration. Proposals on the nature of the interaction between Complex III, cytochrome c and cytochrome c oxidase are considered in the light of these results.

scholarly journals Membrane topology of beef-heart ubiquinone-cytochrome c reductase (complex III).

1981 ◽  
Vol 256 (21) ◽  
pp. 11132-11136 ◽  
Author(s):  
H. Gutweniger ◽  
R. Bisson ◽  
C. Montecucco
Keyword(s):  
Cytochrome C ◽  
Membrane Topology ◽  
Complex Iii ◽  
Beef Heart ◽  
Cytochrome C Reductase

scholarly journals Pathology of Mitochondrial Encephalomyopathies

2005 ◽  
Vol 32 (2) ◽  
pp. 152-166 ◽  
Author(s):  
Harvey B. Sarnat ◽  
José Marín-García
Keyword(s):  
Cytochrome C ◽  
Succinate Dehydrogenase ◽  
Cytochrome C Oxidase ◽  
Oxidase Activity ◽  
Morphological Evidence ◽  
Regular Feature ◽  
Complex Iv ◽  
Genetic Studies ◽  
Mitochondrial Encephalomyopathies ◽  
Mitochondrial Cytopathy

ABSTRACT:Muscle biopsy provides the best tissue to confirm a mitochondrial cytopathy. Histochemical features often correlate with specific syndromes and facilitate the selection of biochemical and genetic studies. Ragged-red fibres nearly always indicate a combination defect of respiratory complexes I and IV. Increased punctate lipid within myofibers is a regular feature of Kearns-Sayre and PEO, but not of MELAS and MERRF. Total deficiency of succinate dehydrogenase indicates a severe defect in Complex II; total absence of cytochrome-c-oxidase activity in all myofibres correlates with a severe deficiency of Complex IV or of coenzyme-Q10. The selective loss of cytochrome-c-oxidase activity in scattered myofibers, particularly if accompanied by strong succinate dehydrogenase staining in these same fibres, is good evidence of mitochondrial cytopathy and often of a significant mtDNA mutation, though not specific for Complex IV disorders. Glycogen may be excessive in ragged-red zones. Ultrastructure provides morphological evidence of mitochondrial cytopathy, in axons and endothelial cells as well as myocytes. Abnormal axonal mitochondria may contribute to neurogenic atrophy of muscle, a secondary chronic feature. Quantitative determinations of respiratory chain enzyme complexes, with citrate synthase as an internal control, confirm the histochemical impressions or may be the only evidence of mitochondrial disease. Biological and technical artifacts may yield falsely low enzymatic activities. Genetic studies screen common point mutations in mtDNA. The brain exhibits characteristic histopathological alterations in mitochondrial diseases. Skin biopsy is useful for mitochondrial ultrastructure in smooth erector pili muscles and axons; skin fibroblasts may be grown in culture. Mitochondrial alterations occur in many nonmitochondrial diseases and also may be induced by drugs and toxins.

scholarly journals The Lebanese Allele in the PET100 Gene: Report on Two New Families with Cytochrome c Oxidase Deficiency

2019 ◽  
Vol 08 (03) ◽  
pp. 172-178 ◽  
Author(s):  
Hicham Mansour ◽  
Sandra Sabbagh ◽  
Sami Bizzari ◽  
Stephany El-Hayek ◽  
Eliane Chouery ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Lactic Acidosis ◽  
Developmental Delay ◽  
Cytochrome C Oxidase ◽  
Brain Magnetic Resonance Imaging ◽  
Global Developmental Delay ◽  
Mitochondrial Complex ◽  
Oxidase Deficiency ◽  
Complex Iv ◽  
Cytochrome C Oxidase Deficiency

AbstractCytochrome c oxidase deficiency is caused by mutations in any of at least 30 mitochondrial and nuclear genes involved in mitochondrial complex IV biogenesis and structure, including the recently identified PET100 gene. Here, we report two families, of which one is consanguineous, with two affected siblings each. In one family, the siblings presented with developmental delay, seizures, lactic acidosis, abnormal brain magnetic resonance imaging, and low muscle mitochondrial complex IV activity at 30%. In the other family, the two siblings, now deceased, had a history of global developmental delay, failure to thrive, muscular hypotonia, seizures, developmental regression, respiratory insufficiency, and lactic acidosis. By whole exome sequencing, a missense mutation in exon 1 of the PET100 gene (c.3G > C; [p.Met1?]) was identified in both families. A review of the clinical description and literature is discussed, highlighting the importance of this variant in the Lebanese population.

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