Structure of Dunaliella photosystem II reveals conformational flexibility of stacked and unstacked supercomplexes

Ido Caspy, Maria Fadeeva, Yuval Mazor, Nathan Nelson

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Photosystem II (PSII) generates an oxidant whose redox potential is high enough to enable water oxidation, a substrate so abundant that it assures a practically unlimited electron source for life on earth. Our knowledge on the mechanism of water photooxidation was greatly advanced by high-resolution structures of prokaryotic PSII. Here, we show high-resolution cryogenic electron microscopy (cryo-EM) structures of eukaryotic PSII from the green alga Dunaliella salina at two distinct conformations. The conformers are also present in stacked PSII, exhibiting flexibility that may be relevant to the grana formation in chloroplasts of the green lineage. CP29, one of PSII associated light-harvesting antennae, plays a major role in distinguishing the two conformations of the supercomplex. We also show that the stacked PSII dimer, a form suggested to support the organisation of thylakoid membranes, can appear in many different orientations providing a flexible stacking mechanism for the arrangement of grana stacks in thylakoids. Our findings provide a structural basis for the heterogenous nature of the eukaryotic PSII on multiple levels.

Original languageEnglish (US)
Article numbere81150
StatePublished - 2023

ASJC Scopus subject areas

  • General Neuroscience
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology


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