Search results for "Ubiquinol"

Isolation and partial characterization of a cytochrome-o complex from chromatophores of the photosynthetic bacterium Rhodospirillum rubrum FR1.

1989

A cytochrome-o complex was isolated from chromatophores of photoheterotrophically grown Rhodospirillum rubrum FR1. The enzyme was extracted with the non-denaturating detergent taurodeoxycholate and subsequently purified by sucrose-density-gradient centrifugation and gel-permeation HPLC. The complex contains two types of cytochromes, one of them cytochrome o, and two copper atoms. It catalyzes the reduction of molecular oxygen, when N,N,N',N'-tetramethyl-p-phenylenediamine or ubiquinol 10 are offered as electron donors. The oxidase activity is inhibited by cyanide, carbon monoxide and 2-heptyl-2-hydroxyquinoline N-oxide. The molecular mass of the protein is 136 +/- 15 kDa. The subunit analys…

A Ubiquinol-Based Charge-Transfer Complex Obtained from a Solvent-Free Approach

2009

The oxidation of ubiquinol by the isolated rieske iron-sulfur protein in solution

1990

The pre-steady-state redox reactions of the Rieske iron-sulfur protein isolated from beef heart mitochondria have been characterized. The rates of oxidation by c-type cytochromes is much faster than the rate of reduction by ubiquinols. This enables the monitoring of the oxidation of ubiquinols by the Rieske protein through the steady-state electron transfer to cytochrome c in solution. The pH and ionic strength dependence of this reaction indicate that the ubiquinol anion is the direct reductant of the oxidized cluster of the iron-sulfur protein. The second electron from ubiquinol is diverted to oxygen by the isolated Rieske protein, and forms oxygen radicals that contribute to the steady-s…

Novel inhibitors of mitochondrial respiratory chain: endoperoxides from the marine tunicate Stolonica socialis.

2001

The Mediterranean tunicate Stolonica socialis contains a new class of powerful cytotoxic acetogenins, generically named stolonoxides. In this paper, which also details the isolation and chemical characterization of a minor component (3a) of the tunicate extract, we report the potent inhibitory activity (IC(50) < 1 microM) of stolonoxides (1a and 3a) on mitochondrial electron transfer. The compounds affect specifically the functionality of complex II (succinate:ubiquinone oxidoreductase) and complex III (ubiquinol:cytochrome C oxidoreductase) in mammalian cells, thereby causing a rapid collapse of the whole energetic metabolism. This result, which differs from the properties of similar known…