Redox- and Light-Driven Hydration Dynamics in Biological Energy Transduction

Biological energy transduction is catalyzed by proteins that electrochemically charge up biological membranes, powered by a chemical reaction or light-capturing process. Recent atomic structures of the respiratory enzymes, the photosynthetic machinery, as well as many light-driven ion pumps, provide together with biophysical and computational experiments a starting point for deriving molecular mechanisms of these fascinating proteins. Based on computational and experimental data, I propose here that general molecular mechanisms are employed to catalyze key charge separation processes in biological energy transduction. An electrostatic perturbation at the redox- or light-activated center is suggested to lead to coupled conformational and hydration changes that in turn modulate the barriers for the proton/ion transfer processes. The mechanistic model is discussed in context of four central energy-transducing proteins: the respiratory complex I (NADH: ubiquinone oxidoreductase), complex IV (cytochrome c oxidase), a light-driven sodium pump (KR2), and photosystem II.