EMD-13898

Single-particle
3.7 Å
EMD-13898 Deposition: 24/11/2021
Map released: 06/04/2022
Last modified: 06/11/2024
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EMD-13898

The structure of Photosystem I tetramer from Chroococcidiopsis TS-821, a thermophilic, unicellular, non-heterocyst-forming cyanobacterium

EMD-13898

Single-particle
3.7 Å
EMD-13898 Deposition: 24/11/2021
Map released: 06/04/2022
Last modified: 06/11/2024
Overview 3D View Sample Experiment Validation Volume Browser Additional data Links
Sample Organism: Chroococcidiopsis sp. TS-821
Sample: Photosystem I
Fitted models: 7qco (Avg. Q-score: 0.326)

Deposition Authors: Semchonok DA , Mondal J
Cryo-EM structure of a tetrameric photosystem I from Chroococcidiopsis TS-821, a thermophilic, unicellular, non-heterocyst-forming cyanobacterium.
PUBMED: 35059628
DOI: doi:10.1016/j.xplc.2021.100248
ISSN: 2590-3462
Abstract:
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.