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 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 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

Ubiquinol–cytochrome-c reductase 7.2 kDa protein of mitochondrial complex III is steroid-responsive and increases in cardiac hypertrophy and hypertension

2007 ◽  
Vol 85 (10) ◽  
pp. 986-996 ◽  
Author(s):  
Hung Huynh ◽  
Nicolas Servant ◽  
Lorraine E. Chalifour
Keyword(s):  
Cytochrome C ◽  
Cardiac Hypertrophy ◽  
Premenopausal Women ◽  
Complex Iii ◽  
Ovariectomized Rats ◽  
Spontaneously Hypertensive ◽  
Cytochrome C Reductase ◽  
Mitochondrial Respiratory Complex ◽  
Wistar Kyoto ◽  
Intact Rats

Women and men do not respond identically to cardiac insults; premenopausal women are somewhat protected from cardiovascular disease. Our objective was to isolate and characterize hormone-responsive genes in the heart. Differential display identified an estrogen-inducible fragment that was found to encode the ubiquinol–cytochrome-c reductase (UCCR) 7.2 kDa protein of the mitochondrial respiratory complex III. We found UCCR7.2 mRNA to be highly expressed in the heart, and this expression increased in hearts of 4-, 10-, and 28-week-old spontaneously hypertensive rats (SHR) compared with normotensive Wistar–Kyoto rats. Oral hydralazine treatment to reduce hypertension reduced SHR UCCR7.2 expression. Cardiac UCCR7.2 mRNA expression was also increased significantly after a 5/6 nephrectomy compared with mock surgery. Cardiac expression after ovariectomy was 50% that of intact rats. Supplementation of ovariectomized rats with estrogen had no effect, whereas progesterone increased cardiac expression, although not to intact levels. No change in cardiac UCCR7.2 expression was found when intact rats were treated with either tamoxifen or ICI 182780. Thus, UCCR7.2 expression is reduced in the absence of ovarian hormones, but is not directly regulated by estrogen in the heart. We conclude that UCCR7.2 is a steroid hormone-responsive gene in the heart, with expression increased in cardiac hypertrophy and in response to hypertension.

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