Cryo-EM structure of a tetrameric photosystem I from Chroococcidiopsis TS-821, a thermophilic, unicellular, non-heterocyst-forming cyanobacterium

Dmitry A. Semchonok, Jyotirmoy Mondal, Connor J. Cooper, Katrina Schlum, Meng Li, Muhamed Amin, Carlos O. S. Sorzano, Erney Ramírez-Aportela, Panagiotis L. Kastritis, Egbert J. Boekema, Albert Guskov, Barry D. Bruce*

*Bijbehorende auteur voor dit werk

OnderzoeksoutputAcademicpeer review

7 Citaten (Scopus)
68 Downloads (Pure)


Photosystem I (PSI) is one of two photosystems involved in oxygenic photosynthesis. PSI of cyanobacteria exists in monomeric, trimeric, and tetrameric forms, in contrast to the strictly monomeric form of PSI in plants and algae. The tetrameric organization raises questions about its structural, physiological, and evolutionary significance. Here we report the ∼3.72 Å resolution cryo-electron microscopy structure of tetrameric PSI from the thermophilic, unicellular cyanobacterium Chroococcidiopsis sp. TS-821. The structure resolves 44 subunits and 448 cofactor molecules. We conclude that the tetramer is arranged via two different interfaces resulting from a dimer-of-dimers organization. The localization of chlorophyll molecules permits an excitation energy pathway within and between adjacent monomers. Bioinformatics analysis reveals conserved regions in the PsaL subunit that correlate with the oligomeric state. Tetrameric PSI may function as a key evolutionary step between the trimeric and monomeric forms of PSI organization in photosynthetic organisms.
Originele taal-2English
Aantal pagina's18
TijdschriftPlant Communications
Nummer van het tijdschrift1
Vroegere onlinedatum13-okt.-2021
StatusPublished - 10-jan.-2022

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