Journal Article

FZJ-2026-04054

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Cryo-EM structures of naturally occurring dimeric photosystem II complexes lacking the Mn4CaO5 cluster

Zhao, Z. ; Vercellino, I.FZJ* ; Whitelegge, J. P. ; Maghlaoui, K. ; Białek, W. ; Nixon, P. J. (Corresponding author) ; Sazanov, L. A. (Corresponding author)

2026
Springer Nature [London]

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Please use a persistent id in citations: doi:10.1038/s41467-026-75324-x

Abstract: 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 report 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.

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Contributing Institute(s):

1. Strukturbiologie (ER-C-3)

Research Program(s):

1. 5352 - Understanding the Functionality of Soft Matter and Biomolecular Systems (POF4-535) (POF4-535)
2. 5241 - Molecular Information Processing in Cellular Systems (POF4-524) (POF4-524)

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