Electron transfer and energy coupling in cytochrome bc₁ Complex

P. L. Dutton, University of Pennsylvania Perelman School of Medicine
C. C. Page, University of Pennsylvania Perelman School of Medicine
X. Chen, University of Pennsylvania Perelman School of Medicine
A. Palmitessa, University of Pennsylvania Perelman School of Medicine
R. E. Sharp, University of Pennsylvania Perelman School of Medicine
H. Ding, University of Pennsylvania Perelman School of Medicine
F. Daldal, University of Pennsylvania Perelman School of Medicine
C. C. Moser, University of Pennsylvania Perelman School of Medicine

Abstract

The figure presents a model of the redox components of cyt bc1, complex. The edgeto-edge distances are consistent with electron transfer kinetic measurements.1,2 The two ubiquinones in the Qo site (Qos strongly and Qow weakly binding) are derived from extensive Qo site mutational studies and ubiquinone extraction-reconstitution.3,4 The large distance (21Å) between the [2Fe2S] and cyt bL accommodating two ubiquinones is one way to safely conduct the primary steps of hydroquinone oxidation in the Qo site with one electron moving down the chain to cyt c2 while initiating transmembrane electron transfer to cyt bL through b H to the Qi site to build up an electrochemical gradient of orotons. 1. Moser. C. C. et al. Nature 355. 1992; 2. Moser, C. C. et al., BBA 1101, 1992; 3. Ding, H. et al., Biochem. 31, 1992; 4. Ding, H. et al., Biochem. 34, 1995.