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. Author manuscript; available in PMC: 2014 Aug 1.
Published in final edited form as: Circ Res. 2014 Jan 31;114(3):524–537. doi: 10.1161/CIRCRESAHA.114.300559

Figure 4.

Figure 4

(A) Superoxide generation mediated by the Q-cycle mechanism in complex III. The scheme is adapted from Ref. (43) with modification. Gray areas symbolize the reactions involved in •O2− production. P, O, and C represent positive, outside, and cytoplasmic side respectively. N, I, and M stands for negative, inside, and matrix side, respectively. Solid bars in brick red show the opposition of electron transfer from the bL to bH by the membrane potential (ΔΨ) and inhibition of bH reoxidation by antimycin A. (B) X-ray structure (pdb 1PPJ) of complex III shows Qo site (occupied by Qo site inhibitor, stigmatellin in green color) is located immediately next to the inter-membrane space. Structure also shows the Qi site (occupied by Qi site inhibitor, antimycin A in blue color) is located next to the matrix site. The subunits of cytochrome b, cytochrome c1, and Rieske iron sulfur protein (RISP) are denoted by cyan, pale green, and yellow ribbons, respectively.