Helmut Kirchhoff - From Molecules to Membranes: Design Principles of Photosynthetic Membranes

More than a billion years of evolution shaped and tuned the photosynthetic apparatus harbored in thylakoid membranes to make energy conversion both efficient and robust in an often-unpredictable ever-changing nature. This success story of biological energy conversion is based on built-in structural flexibilities of the photosynthetic machinery that allows for a dynamic response on environmental cues. These structural alterations of the thylakoid membrane network occur on three different length scales ranging from the molecular level (Å - few 10 nm), the meosocopic level (several 10 nm – several 100 nm), to the overall membrane level (m). Classification into these three structural levels turned out to be extremely helpful since different physicochemical principles are realized at different length scales which require different methodical approaches to study them. The talk surveys examples for structural alterations on all three levels. In detail, for the molecular level, data on lipid-protein interactions will be presented that show the impact of highly abundant non-bilayer lipids for the structure and function of light-harvesting protein complexes. For the mesoscopic level, the significance of a supra-molecular protein reorganization from disordered to highly ordered semicrystalline arrays will be unraveled. Finally, it will be demonstrated that dynamic swelling and shrinkage of the entire membrane system is a crucial structural alteration for the control of diffusion-dependent electron transport and protein repair processes. Unraveling the design principals for the three structural levels and their interdependency is indispensible for a holistic understanding and modeling of photosynthetic energy conversion.