Mitochondrial XXXX radical formation is controlled by electron bifurcation to the high and low potential pathways.

@entity15401 @entity8581 @entity26 @entity224 @entity5985
The generation of @entity26 radicals in biological systems and their sites of intracellular release have been subject of numerous studies in the last decades. Based on these studies mitochondria are considered to be the major source of intracellular @entity26 radicals. Although this finding is more or less accepted, the mechanism of univalent @entity26 reduction in mitochondria is still obscure. One of the most critical electron transfer steps in the respiratory chain is the electron bifurcation at the cytochrome bc1 complex. Recent studies with genetically mutated mitochondria have made it clear that electron bifurcation from @entity15401 to the cytochrome bc1 complex requires the free mobility of the head domain of the Rieske @entity5985 protein. On the other hand, it has been long known that inhibition of electron bifurcation by @entity8581 causes leakage of single electrons to @entity26 , which results in the release of @entity224 radicals. These findings lead us to study whether hindrance of the interaction of @entity15401 with the cytochrome bc1 complex is the regulator of single electron diversion to @entity26 . Hindrance of electron bifurcation was observed following alterations of the physical state of membrane phospholipids in which the cytochrome bc1 complex is inserted. Irrespective of whether the fluidity of the membrane lipids was elevated or decreased, electron flow rates to the Rieske @entity5985 protein were drastically reduced. Concomitantly @entity224 radicals were released from these mitochondria, strongly suggesting an effect on the mobility of the head domain of the Rieske @entity5985 protein. This revealed the involvement of the @entity15401 cytochrome bc1 redox couple in mitochondrial @entity224 formation. The regulator, which controls leakage of electrons to @entity26 , appears to be the electron-branching activity of the cytochrome bc1 complex.
