Structure of Cytochrome bc Complex from Bovine Heart Mitochondria

Structure of Cytochrome bc Complex from Bovine Heart Mitochondria 

All known cytochrome bc complexes have three essential subunits, which contain all four redox centers in common. These subunits are cytochrome b (cyt. b), cytochrome ( (cyt. c ), and the Rieske [2Fe-2S] protein (ISP). The redox centers are heme b i and heme b in cytochrome b (L and H represent low and high potential, respectively), heme C in cytochrome ci, and Rieske [2Fe-2S] (FeS) cluster in ISP. 

Redox-Active Subunits and the Proton Motive Qcycle 

The reaction mechanism of cytochrome bc complex is known as the proton motive Qcycle originally proposed by Peter Mitchell (Mitchell, 1976). This mechanism is the basis of his chemiosmotic theory for which he was awarded the Nobel prize in 1978. Since then, the enzyme has been characterized extensively using various techniques. Redox centers have been characterized spectroscopically (for review, see Trumpower and Gennis, 1994), electron transfer pathways have been determined using kinetic experiments with specific inhibitors (De Vries 1986 Zhu et al., 1984), and the positions of quinone binding sites and redox centers have been determined using biochemical and mutational analysis (for review, see Esposti et al, 1993 Brasseur et al, 1996). As a result of these efforts, the latest modified Qcycle has been widely accepted by researchers in the field (for reviews, see Crofts et al, 1983 Trumpower, 1990 Berry et al, 2000). 

Rieske iron-sulfur protein Cyt. c Cytochrome c Cyt. Ci Cytochrome c, 

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II. Structure of Cytochrome bc Complex from Bovine Heart Mitochondria. .. 153... 

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