Structural Basis of Multifunctional Bovine Mitochondrial Cytochrome bc1 Complex
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- Yu, CA., Tian, H., Zhang, L. et al. J Bioenerg Biomembr (1999) 31: 191. doi:10.1023/A:1005411510913
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The mitochondrial cytochrome bc1 complex is a multifunctional membrane protein complex. Itcatalyzes electron transfer, proton translocation, peptide processing, and superoxide generation.Crystal structure data at 2.9 Å resolution not only establishes the location of the redox centersand inhibitor binding sites, but also suggests a movement of the head domain of the iron–sulfurprotein (ISP) during bc1 catalysis and inhibition of peptide-processing activity during complexmaturation. The functional importance of the movement of extramembrane (head) domain ofISP in the bc1 complex is confirmed by analysis of the Rhodobacter sphaeroides bc1 complexmutants with increased rigidity in the ISP neck and by the determination of rate constants foracid/base-induced intramolecular electron transfer between [2Fe–2S] and heme c1 in nativeand inhibitor-loaded beef complexes. The peptide-processing activity is activated in bovineheart mitochondrial bc1 complex by nonionic detergent at concentrations that inactivate electrontransfer activity. This peptide-processing activity is shown to be associated with subunits Iand II by cloning, overexpression and in vitro reconstitution. The superoxide-generation siteof the cytochrome bc1 complex is located at reduced bL and Q•−. The reaction is membranepotential-, and cytochrome c-dependent.