The Q-cycle reviewed: How well does a monomeric mechanism of the bc(1) complex account for the function of a dimeric complex?

ABSTRACT: Recent progress in understanding the Q-cycle mechanism of the bc(1) complex is reviewed. The data strongly support a mechanism in which the Q(o)-site operates through a reaction in which the first electron transfer from ubiquinol to the oxidized iron-sulfur protein is the rate-determining step for the overall process. The reaction involves a proton-coupled electron transfer down a hydrogen bond between the ubiquinol and a histidine ligand of the [2Fe-2S] cluster, in which the unfavorable protonic configuration contributes a substantial part of the activation barrier. The reaction is endergonic, and the products are an unstable ubisemiquinone at the Q(o)-site, and the reduced iron-sulfur protein, the extrinsic mobile domain of which is now free to dissociate and move away from the site to d

SUBMITTER: Crofts AR 

PROVIDER: S-EPMC2578832 | biostudies-literature | 2008 Jul-Aug

REPOSITORIES: biostudies-literature