Structure of a tetrameric photosystem I from a glaucophyte alga Cyanophora paradoxa

Koji Kato, Ryo Nagao, Yoshifumi Ueno, Makio Yokono, Takehiro Suzuki, Tian Yi Jiang, Naoshi Dohmae, Fusamichi Akita, Seiji Akimoto, Naoyuki Miyazaki, Jian Ren Shen

Research output: Contribution to journalArticlepeer-review


Photosystem I (PSI) is one of the two photosystems functioning in light-energy harvesting, transfer, and electron transfer in photosynthesis. However, the oligomerization state of PSI is variable among photosynthetic organisms. We present a 3.8-Å resolution cryo-electron microscopic structure of tetrameric PSI isolated from the glaucophyte alga Cyanophora paradoxa, which reveals differences with PSI from other organisms in subunit composition and organization. The PSI tetramer is organized in a dimer of dimers with a C2 symmetry. Unlike cyanobacterial PSI tetramers, two of the four monomers are rotated around 90°, resulting in a completely different pattern of monomer-monomer interactions. Excitation-energy transfer among chlorophylls differs significantly between Cyanophora and cyanobacterial PSI tetramers. These structural and spectroscopic features reveal characteristic interactions and excitation-energy transfer in the Cyanophora PSI tetramer, suggesting that the Cyanophora PSI could represent a turning point in the evolution of PSI from prokaryotes to eukaryotes.

Original languageEnglish
Article number1679
JournalNature communications
Issue number1
Publication statusPublished - Dec 2022

ASJC Scopus subject areas

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Physics and Astronomy(all)


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