Cytochrome bc(1) is a major component of biological energy conversion that exploits an energetically favourable redox reaction to generate a transmembrane proton gradient. Since the mechanistic details of the coupling of redox and protonation reactions in the active sites are largely unresolved, we have identified residues that undergo redox-linked protonation state changes. Structure-based Poisson-Boltzmann/Monte Carlo titration calculations have been performed for completely reduced and completely oxidised cytochrome bc(1). Different crystallographically observed conformations of Glu272 and surrounding residues of the cytochrome b subunit in cytochrome bc(1) from Saccharomyces cerevisiae have been considered in the calculations. Coenzyme Q (CoQ) has been modelled into the CoQ oxidation site (Q(o)-site). Our results indicate that both conformational and protonation state changes of Glu272 of cytochrome b may contribute to the postulated gating of CoQ oxidation. The Rieske iron-sulphur cluster could be shown to undergo redox-linked protonation state changes of its histidine ligands in the structural context of the CoQ-bound Q(o)-site. The proton acceptor role of the CoQ ligands in the CoQ reduction site (Q(i)-site) is supported by our results. A modified path for proton uptake towards the Q(i)-site features a cluster of conserved lysine residues in the cytochrome b (Lys228) and cytochrome c(1) subunits (Lys288, Lys289, Lys296). The cardiolipin molecule bound close to the Q(i)-site stabilises protons in this cluster of lysine residues.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|