Life-science research at the borders of biology, chemistry, and physics has facilitated identification of key principles of protein function, e.g., the key-and-lock principle in substrate binding. The research in the SFB 1078 aims at a further principle: Complex protein functions are coordinated and facilitated by evolutionary optimized protonation dynamics.
In phytochromes of plants and cyanobacteria, a pigment absorbs light and a remote protein domain passes on the light signal. Not only in phytochromes but in complex proteins in general, various functional sites or domains need to work in a coordinated way. This is facilitated – according to our central working hypothesis – by distinct protonation dynamics. The term ‘protonation dynamics’ includes the local relocation of protons within hydrogen-bonded networks of amino-acid residues and water molecules as well as the directed long-distance proton transfer and associated changes of long-range electrostatic interactions. To address this general hypothesis efficiently, four specific protein systems were selected that are particularly well suited to clarify complementary aspects of protonation dynamics. The coupling of protonation dynamics to multi-site redox reactions is investigated in photosystem II (photosynthetic water oxidation) and cytochrome c oxidase (oxygen reduction and proton pumping in respiration). The interrelation between protonation dynamics and conformational changes in light-reception, signal transduction and ion-channel conductance is investigated in channelrhodopsins (light-gated cation channels) and phytochromes (bi-stable photoreceptor proteins controlling kinase activity).
It is our goal to understand, by means of exemplary investigations on the four selected protein systems, the role of protonation dynamics in protein function at a basic physical-chemical level. To achieve this goal, we use a combination of new biophysical experiments with molecular simulations and quantum-chemical computations. Albeit the research program is focused on basic questions, it could inspire new approaches in energy sciences (light-driven water oxidation, oxygen reduction) and support the development of new tools in medical sciences (knowledge-based customization of channel rhodopsins for application in neurosciences) and biotechnology (photoreceptors in light-controlled gene expression).