Structural Basis and Mechanism of Proton Translocation in Complex I and Complex III

Abstract

Proton pumping respiratory complexes drive the energy conversion in cellular respiration by coupling electron and proton transfer via defined mechanisms. In complex I and complex III, bypass reactions result in production of reactive oxygen species (ROS) which are implicated in diseases and physiological processes of aging. Structure and Q cycle mechanism of complex III are in general well described [1]. Yet, several key features of the mechanism, such as the oxidation of ubiquinol, pathways for proton uptake and release and ROS production are still in question and will be discussed. Elucidation of structure and mechanism of complex I is only at its beginning. X-ray crystallographic analysis of the largest and most complicated respiratory membrane protein complex revealed the structural basis for a new mechanism of proton pumping by conformational coupling [2]. Data of the structural analysis will be presented.