The reaction center (RC)-light-harvesting complex 1 (LH1) supercomplex plays a pivotal role in bacterial photosynthesis. Many RC-LH1 complexes integrate an additional protein PufX that is key for bacterial growth and photosynthetic competence. Here, we present a cryo-electron microscopy structure of the RC-LH1-PufX supercomplex from at 2.8-Å resolution. The RC-LH1-PufX monomer contains an LH ring of 15 αβ-polypeptides with a 30-Å gap formed by PufX. PufX acts as a molecular "cross brace" to reinforce the RC-LH1 structure. The unusual PufX-mediated large opening in the LH1 ring and defined arrangement of proteins and cofactors provide the molecular basis for the assembly of a robust RC-LH1-PufX supercomplex and efficient quinone transport and electron transfer. These architectural features represent the natural strategies for anoxygenic photosynthesis and environmental adaptation.
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Cryo-EM structure of a monomeric RC-LH1-PufX supercomplex with high-carotenoid content from Rhodobacter capsulatus.
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Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK; College of Marine Life Sciences and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China. Electronic address:
Article Synopsis
- Researchers investigated the structure of the photochemical reaction center (RC) and light-harvesting complex 1 (LH1) in purple photosynthetic bacteria, focusing on Rhodobacter capsulatus.
- They used cryoelectron microscopy to reveal that Rba. capsulatus forms monomeric RC-LH1 complexes with a 15-subunit LH1 ring, where the incorporation of a protein called PufX creates a significant opening.
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Cryo-EM structure of the photosynthetic RC-LH1-PufX supercomplex at 2.8-Å resolution.
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Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
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