Marc Nowaczyk | Structural insights into photosystem II assembly
Channel: CyanoWorld
Date: 19/03/2021

Marc Nowaczyk - Ruhr University Bochum, Germany

Homepage: https://www.ruhr-uni-bochum.de/photosynthesis/
Twitter: https://twitter.com/NowaLab
Research Gate: https://www.researchgate.net/profile/Marc-Nowaczyk

Structural insights into photosystem II assembly

Membrane protein complexes play a central role in cyanobacterial bioenergetics. We have recently solved several structures of cyanobacterial membrane protein complexes by cryo-electron microscopy and complemented the work by spectroscopic analysis or molecular dynamics simulation (Schuller et al. 2019, Schuller et al. 2020). Photosystem II (PSII) is one of the best-studied photosynthetic multi-subunit membrane protein complexes so far. It catalyzes a very unique reaction: the light-driven oxidation of water. Many details of PSII structure and function have been unraveled already. However, the molecular details of its biogenesis, particularly the role of auxiliary proteins, which assist the assembly of the various cofactors and subunits, remained unclear (Heinz et al 2016). Using cryo-electron microscopy, we solved the structure of a partially functional PSII assembly intermediate from the thermophilic cyanobacterium Thermosynechococcus elongatus at 2.94 Å resolution (Zabret et al. 2020). It contains three assembly factors (Psb27, Psb28, Psb34) and provides detailed insights into their molecular function. Binding of Psb28 induces large conformational changes at the PSII acceptor side, which distorts the binding pocket of the mobile quinone (QB) and replaces the bicarbonate ligand of non-heme iron with glutamate, a structural motif found in reaction centers of non-oxygenic photosynthetic bacteria. These results reveal novel mechanisms that protect PSII from damage during biogenesis until water splitting is activated. Our structure further demonstrates how the PSII active site is prepared for the incorporation of the Mn4CaO5 cluster, which performs the unique water-splitting reaction.

This talk is part of the CyanoWorld online seminar series, hosted by Nicolas Schmelling and Ilka Axmann, and was held on Zoom on March 11th, 2021.

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