PT  - JOURNAL ARTICLE
AU  - Jure Zabret
AU  - Stefan Bohn
AU  - Sandra K. Schuller
AU  - Oliver Arnolds
AU  - Madeline Möller
AU  - Jakob Meier-Credo
AU  - Pasqual Liauw
AU  - Aaron Chan
AU  - Emad Tajkhorshid
AU  - Julian D. Langer
AU  - Raphael Stoll
AU  - Anja Krieger-Liszkay
AU  - Benjamin D. Engel
AU  - Till Rudack
AU  - Jan M. Schuller
AU  - Marc M. Nowaczyk
TI  - How to build a water-splitting machine: structural insights into photosystem II assembly
AID  - 10.1101/2020.09.14.294884
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.09.14.294884
4099  - http://biorxiv.org/content/early/2020/09/15/2020.09.14.294884.short
4100  - http://biorxiv.org/content/early/2020/09/15/2020.09.14.294884.full
AB  - Biogenesis of photosystem II (PSII), nature’s water splitting catalyst, is assisted by auxiliary proteins that form transient complexes with PSII components to facilitate stepwise assembly events. Using cryo-electron microscopy, we solved the structure of such a PSII assembly intermediate with 2.94 Å resolution. 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 distort the binding pocket of the mobile quinone (QB) and replace bicarbonate with glutamate as a ligand of the non-heme iron, 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.One Sentence Highlight The high-resolution Cryo-EM structure of the photosystem II assembly intermediate PSII-I reveals how nature’s water splitting catalyst is assembled, protected and prepared for photoactivation by help of the three assembly factors Psb27, Psb28 and Psb34.Competing Interest StatementThe authors have declared no competing interest.