J Integr Plant Biol. ›› 2023, Vol. 65 ›› Issue (1): 223-234.DOI: 10.1111/jipb.13367

• Photosynthesis and Crop Physiology • Previous Articles     Next Articles

Cryo-electron microscopy structure of the intact photosynthetic light-harvesting antenna-reaction center complex from a green sulfur bacterium

Jing-Hua Chen1,2*, Weiwei Wang1, Chen Wang2, Tingyun Kuang3, Jian-Ren Shen3,4*, Xing Zhang2,5*   

  1. 1. College of Life Science Zhejiang University Hangzhou 310058 China;
    2. Department of Pathology of Sir Run Run Shaw Hospital, and Department of Biophysics Zhejiang University School of Medicine Hangzhou 310058 China;
    3. Key Laboratory of Photobiology, Institute of Botany, Photosynthesis Research Center the Chinese Academy of Sciences Beijing 100093 China;
    4. Research Institute for Interdisciplinary Science, and Graduate School of Natural Science and Technology Okayama University Okayama 700-8530 Japan;
    5. Center of Cryo Electron Microscopy Zhejiang University School of Medicine Hangzhou 310058 China
    *Correspondences: Jing‐Hua Chen (jhchentop@163.com); Jian‐Ren Shen (shen@cc.okayama-u.ac.jp); Xing Zhang (xzhang1999@zju.edu.cn, Dr. Zhang is fully responsible for the distributions of all materials associated with this article)
  • Received:2022-08-14 Accepted:2022-09-19 Online:2022-09-22 Published:2023-01-01

Abstract: The photosynthetic reaction center complex (RCC) of green sulfur bacteria (GSB) consists of the membrane-imbedded RC core and the peripheric energy transmitting proteins called Fenna–Matthews–Olson (FMO). Functionally, FMO transfers the absorbed energy from a huge peripheral light-harvesting antenna named chlorosome to the RC core where charge separation occurs. In vivo, one RC was found to bind two FMOs, however, the intact structure of RCC as well as the energy transfer mechanism within RCC remain to be clarified. Here we report a structure of intact RCC which contains a RC core and two FMO trimers from a thermophilic green sulfur bacterium Chlorobaculum tepidum at 2.9?? resolution by cryo-electron microscopy. The second FMO trimer is attached at the cytoplasmic side asymmetrically relative to the first FMO trimer reported previously. We also observed two new subunits (PscE and PscF) and the N-terminal transmembrane domain of a cytochrome-containing subunit (PscC) in the structure. These two novel subunits possibly function to facilitate the binding of FMOs to RC core and to stabilize the whole complex. A new bacteriochlorophyll (numbered as 816) was identified at the interspace between PscF and PscA-1, causing an asymmetrical energy transfer from the two FMO trimers to RC core. Based on the structure, we propose an energy transfer network within this photosynthetic apparatus.

Key words: cryo-electron microscopy, energy transfer, FMO protein, green sulfur bacterium, photosynthesis, reaction center

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