Chapter 8: Advances in Understanding Mechanism and Physiology of Cytochromes bc

Cytochrome bc-type complexes are the key proteins of respiratory and photosynthetic electron transport chains involved in conservation of energy. They use quinone redox chemistry to translocate protons across the membrane. Here we describe mechanistic and physiologic aspects of operation of these enzymes focusing on new structural and kinetic elements of action of the catalytic sites inferred from recent experimental studies and molecular dynamics simulations. In particular, we discuss the possible mechanism of control of superoxide generation by one of the catalytic sites in the context of recently discovered radical intermediate states of catalysis.