7QCO

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

Replaces:  6QWJ

Summary for 7QCO

• Entry DOI: 10.2210/pdb7qco/pdb
• EMDB information: 13898
• Descriptor: Photosystem I P700 chlorophyll a apoprotein A1, Photosystem I reaction center subunit XI, Photosystem I reaction center subunit XII, ... (16 entities in total)
• Functional Keywords: photosystem i, photosynthesis, cyanobacterium chroococcidiopsis sp. ts-821
• Biological source: Chroococcidiopsis sp. TS-821; More
• Total number of polymer chains: 44
• Total formula weight: 1441058.29

Authors

Semchonok, D.A.,Mondal, J.,Cooper, J.C.,Schlum, K.,Li, M.,Amin, M.,Sorzano, C.O.S.,Ramirez-Aportela, E.,Kastritis, P.L.,Boekema, E.J.,Guskov, A.,Bruce, B.D. (deposition date: 2021-11-24, release date: 2022-04-06, Last modification date: 2024-11-06)

Primary citation

Semchonok, D.A.,Mondal, J.,Cooper, C.J.,Schlum, K.,Li, M.,Amin, M.,Sorzano, C.O.S.,Ramirez-Aportela, E.,Kastritis, P.L.,Boekema, E.J.,Guskov, A.,Bruce, B.D.
Cryo-EM structure of a tetrameric photosystem I from Chroococcidiopsis TS-821, a thermophilic, unicellular, non-heterocyst-forming cyanobacterium.
Plant Commun., 3:100248-100248, 2022

PubMed 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 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.

PubMed: 35059628
DOI: 10.1016/j.xplc.2021.100248

Experimental method

ELECTRON MICROSCOPY (3.7 Å)