Researchers of the Department of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, and the Max Planck Research Group of the Małopolska Centre of Biotechnology, Jagiellonian University, carried out a joint research project aimed at understanding photosynthetic processes at the atomic level. Their findings were published in the journal Science Advances.
The research teams headed by Prof. dr hab. Artur Osyczka and dr hab. Sebastian Glatt ? winners of the FNP’s TEAM and TEAM TECH Core Facility programmes ? succeeded in obtaining high-resolution cryo-EM structures of the protein complex cytochrome b6f, one of the key proteins of photosynthesis. This protein acts as an electron carrier between plastoquinol and plastocyanin, linking other important protein complexes ? photosystems ? into a functional whole.
The first structure (at 2.7 ? resolution) reveals how plastocyanin binds to dimeric cytochrome b6f complex to efficiently accept electron released during the catalytic reaction. It unexpectedly shows only one plastocyanin in the dimer. The second structure (at a remarkable 2.1 ? resolution) identifies a chain of plastoquinone molecules lining up one after another in a manner implicating existence of a channel in each monomer with spatially distinct entrance and exit points. This suggests an entirely new and unanticipated traffic of quinones in which they flow through the channel in one direction, transiently passing through the catalytic site. The proposed mechanism differs from the previously considered reaction scheme where the substrate and product were assumed to use the exact same channel to enter and leave the catalytic site. In addition, the structure revealed the presence of an unexpected cytochrome b6f binding partner, namely thylakoid soluble phosphoprotein TSP9 (protein restricted to higher plants), bound in the highly specific manner at the site presumed to be important for controlling the photosynthetic electron flow. The first author Marcin Sarewicz (Department of Molecular Biophysics, FBBB) explains ? ?Our discovery provides new perspective on understanding the mechanism of regulation of photosynthesis at the level of cytochrome b6f with participation of TSP9 protein.?
Artur Osyczka (Department of Molecular Biophysics, FBBB) summarizes ? ?Overall, it is expected that new structural information provided by the published structures will contribute to our better understanding of the molecular basis of the energetic efficiency of photosynthesis and will inspire further spectroscopic and kinetic explorations.? Sebastian Glatt (Max Planck Research Group, MCB) adds ? ?Because of the exceptionally high resolution – this is so far the best-resolved structure of cytochrome b6f from higher plants – the structures will provide useful models for quantum mechanical calculations aimed at further unraveling physico-chemical basis of key photosynthetic reactions catalyzed by cytochrome b6f.? The study also exemplifies how researchers from different research units at the Jagiellonian University can team up and efficiently work together to deliver scientific results at the world class level.
The team first isolated and characterized biochemically the proteins from spinach leaves at FBBB and then prepared all samples for structural analysis at the MCB Structural Biology Core Facility. All data were collected at the Titan Krios G3i high-end cryo-electron microscope located at SOLARIS National Synchrotron Radiation Centre.
The project was financed from European Funds under the Smart Growth Operational Programme with funding awarded by the Foundation for Polish Science as part of the TEAM (headed by Prof. A. Osyczka) and TEAM TECH Core Facility (headed by dr hab. S. Glatt) programmes.
- the study in Science Advances;
- about the TEAM programme;
- about the TEAM TECH Core Facility programme.