Cyanobacterial sunglasses - How to tune solar energy harvest at the molecular level? - The 85th Meeting of the Israel Chemical Society

Dvir Harris ¹ Fernando Muzzopappa ² Fabian Glaser ³ Adjele Wilson ² Diana Kirilovsky ² Noam Adir ⁴

¹Department of Chemistry, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA
²Institute for Integrative Biology of the Cell (I2bc), Cea, Cnrs,, Université Paris-Sud, Université Paris-Saclay, Gif Sur Yvette, France
³Department of Biology, Lorry I. Lokey Interdisciplinary Center for Life Sciences and Engineering,, Technion – Israel Institute of Technology, Haifa, Israel
⁴Schulich Faculty of Chemistry, Technion – Israel Institute of Technology, Haifa, Israel

Photosynthetic organisms utilize solar energy to sustain themselves in ever-changing natural conditions. The photosynthetic process is initiated by solar energy harvesting, supported by designated antenna complexes. The role of the antenna is to widen the spectrum of absorbed light and transfer and orient this excitation energy (EET) towards the photosynthetic reaction centers (RCs), where electrons are then excited and eventually used for atmospheric carbon fixation and metabolism. Cyanobacteria are oxygen-evolving photosynthetic prokaryote organisms, which were first to exploit water as the primary source of light-dependent electron transfer. In the case of cyanobacteria, the light harvesting complex is the phycobilisome (PBS), which is a gigantic, chromophore-binding, protein complex. However, high-light conditions may be deleterious for photosynthetic oeganisms, as over-excitation of RCs may occur, leading to the formation of reactive oxygen species. It has been long known that cyanobacterial photoprotection is achieved by the interaction between the PBS and the orange carotenoid protein (OCP). However, the exact nature of this interaction has been quite elusive.

In my talk, I will describe a part of my PhD work, which pertained two cardinal Q`s about this system:

1. What are the structural features enabling the dynamics of the hydrophobic carotenoid in to- and out from- the hydrophilic OCP, which are crucial for succesful photoprotection?

2. What is the structural premise facilitating the photoprotective interaction between the OCP and PBS?