@article{Zhao:2026,
author = {Zhao, Z and Vercellino, I and Whitelegge, JP and Maghlaoui, K and Biaek, W and Nixon, PJ and Sazanov, LA},
journal = {Nature Communications},
title = {Cryo-EM structures of naturally occurring dimeric photosystem II complexes lacking the MnCaO cluster},
year = {2026}
}

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TY  - JOUR
AB  - Robust oxygenic photosynthesis requires the efficient assembly and repair of the multi-subunit oxygen-evolving photosystem II (PSII) complex. Previous cryogenic electron microscopy (cryo-EM) structures of PSII assembly/disassembly intermediates have relied on the analysis of deletion mutants or removal of PSII subunits in vitro. Here we determine the cryo-EM structures of naturally occurring dimeric PSII intermediates from the cyanobacterium Thermosynechococcus vestitus at a resolution of about 2.2 Å. These intermediates contain inactive dimers lacking the oxygen-evolving complex (OEC) and semi-active dimers with the OEC present in one of the two monomers. Our structural data provide a mechanism for how assembly and disassembly of the Mn4CaO5 cluster is coordinated with the binding and release of the extrinsic proteins: restructuring of the C-terminal tail of D1 subunit during assembly or disassembly of the Mn cluster triggers conformational changes in D2, CP47 and CP43 to drive the binding/release of the extrinsic proteins. A combination of structural and mass spectrometry data also suggests that the inactive PSII complexes may include damaged complexes containing oxidized D1-His332, a monodentate ligand to one of the Mn ions of the OEC.
AU  - Zhao,Z
AU  - Vercellino,I
AU  - Whitelegge,JP
AU  - Maghlaoui,K
AU  - Biaek,W
AU  - Nixon,PJ
AU  - Sazanov,LA
PY  - 2026///
SN  - 2041-1723
TI  - Cryo-EM structures of naturally occurring dimeric photosystem II complexes lacking the MnCaO cluster
T2  - Nature Communications
ER  - 

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