29] Isolation of a three-subunit cytochrome bc1 complex from Paracoccus denitrificans

Abstract

This chapter discusses the method for purification of a cytochrome bc1 (ubiquinol-cytochrome c oxidoreductase) complex from membranes of the gram-negative soil bacterium Paracoccus denitrificans to isolate respiratory chain components from this bacterium. This respiratory chain complex, containing cytochromes b and c1 and the Rieske-type iron-sulfur protein, has a very high turnover number in a ubiquinol-cytochrome c reductase assay, and this activity is sensitive to antimycin and myxothiazol, inhibitors of the mitochondrial complex. The isolation of the three-subunit bc1 complex, coupled with the isolation of a ubiquinol oxidase “super complex” from this same bacterium, elucidates the structural basis of electron transfer and energy transduction in the respiratory chain. The Paracoccus bc1 complex has the same prosthetic groups and functional activity as the mitochondrial bc1 complex. The chapter also highlights the properties of the Paracoccus cytochrome bc1 complex.