Jure Zabret, Stefan Bohn, Sandra K. Schuller, Oliver Arnolds, Madeline
Möller, Jakob Meier-Credo, Pasqual Liauw, Aaron Chan, Emad Tajkhorshid,
Julian D. Langer, Raphael Stoll, Anja Krieger-Liszkay, Benjamin D. Engel,
Till Rudack, Jan M. Schuller, and Marc M. Nowaczyk.
Structural insights into photosystem II assembly.
Nature Plants, 7:524-538, 2021.
ZABR2021-ET
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 from Thermosynechococcus elongatus at 2.94 Å
resolution. It
contains three assembly factors (Psb27, Psb28 and 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 the bicar-bonate
ligand of non-haem iron with glutamate, a structural motif
found
in reaction centres of non-oxygenic photosynthetic bacteria.
These
results reveal 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 Mn_4CaO_5 cluster, which performs the unique water-
splitting
reaction.
