Integrative Biology Journals
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J Integr Plant Biol. ›› 2025, Vol. 67 ›› Issue (4): 967-978.DOI: 10.1111/jipb.13853

• Research Articles • Previous Articles     Next Articles

Cryo-EM structure of a minimal reaction center-light-harvesting complex from the phototrophic bacterium Chloroflexus aurantiacus

Guoqiang Huang1,2†, Shishang Dong3†, Lin Ma3†, Lin Li3, Jinxin Ju3, Mei-Jiao Wang4, Jian-Ping Zhang4, Sen-Fang Sui1,5,*, Xiaochun Qin3,*   

  1. 1. State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China;
    2. Multiscale Research Institute of Complex Systems, Fudan University, Shanghai 200433, China;
    3. School of Biological Science and Technology, University of Jinan, Jinan 250022, China;
    4. School of Chemistry and Life Resources, Renmin University of China, Beijing 100872, China;
    5. School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
  • Received:2024-06-05 Accepted:2025-01-10 Online:2025-02-06 Published:2025-04-01
  • Contact: *Sen-Fang Sui (suisf@mail.tsinghua.edu.cn); Xiaochun Qin (bio_qinxc@ujn.edu.cn; Dr. Qin is fully responsible for the distributions of all materials associated with this article)
  • About author:†These authors contributed equally to this work.
  • Supported by:
    National Natural Science Foundation of China (32270260, 32070267, 32200206, 32241030, and 32271245), the Taishan Scholars Project (tsqn20240516), and the Shandong Provincial Natural Science Foundation, China (ZR2019ZD48 and ZR2020QC057).

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Abstract: Photosynthetic organisms have developed various light-harvesting antenna systems to capture light and transfer energy to reaction centers (RCs). Simultaneous utilization of the integral membrane light-harvesting antenna (LH complex) and the extrinsic antenna (chlorosomes) makes the phototrophic bacterium Chloroflexus (Cfx.) aurantiacus an ideal model for studying filamentous anoxygenic phototrophs (FAPs). Here, we determined the structure of a minimal RC-LH photocomplex from Cfx. aurantiacus J-10-fl (CaRC-LH) at 3.05-Å resolution. The CaRC-LH binds only to seven LH subunits, which form a crescent-shaped antenna surrounding the movable menaquinone-10 (QB) binding site of CaRC. In this complex with minimal LH units, an extra antenna is required to ensure sufficient light-gathering, providing a clear explanation for the presence of chlorosomes in Cfx. aurantiacus. More importantly, the semicircle of the antenna represents a novel RC-LH assembly pattern. Our structure provides a basis for understanding the existence of chlorosomes in Cfx. aurantiacus and the possible assembly pattern of RC-LH.

Key words: Chloroflexus aurantiacus, chlorosomes, electron transfer, photosynthesis, RC-LH

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