8J5P

Cryo-EM structure of native RC-LH complex from Roseiflexus castenholzii at 2,000lux

Summary for 8J5P

• Entry DOI: 10.2210/pdb8j5p/pdb
• EMDB information: 35989
• Descriptor: Beta subunit of light-harvesting 1, beta,psi-caroten-4-one, PROTOPORPHYRIN IX CONTAINING FE, ... (15 entities in total)
• Functional Keywords: rc-lh core complex, photosynthesis
• Biological source: Roseiflexus castenholzii DSM 13941; More
• Total number of polymer chains: 36
• Total formula weight: 357677.53

Authors

Xu, X.,Xin, J. (deposition date: 2023-04-24, release date: 2023-09-20, Last modification date: 2024-11-06)

Primary citation

Xin, J.,Shi, Y.,Zhang, X.,Yuan, X.,Xin, Y.,He, H.,Shen, J.,Blankenship, R.E.,Xu, X.
Carotenoid assembly regulates quinone diffusion and the Roseiflexus castenholzii reaction center-light harvesting complex architecture.
Elife, 12:-, 2023

PubMed Abstract: Carotenoid (Car) pigments perform central roles in photosynthesis-related light harvesting (LH), photoprotection, and assembly of functional pigment-protein complexes. However, the relationships between Car depletion in the LH, assembly of the prokaryotic reaction center (RC)-LH complex, and quinone exchange are not fully understood. Here, we analyzed native RC-LH (nRC-LH) and Car-depleted RC-LH (dRC-LH) complexes in , a chlorosome-less filamentous anoxygenic phototroph that forms the deepest branch of photosynthetic bacteria. Newly identified exterior Cars functioned with the bacteriochlorophyll B800 to block the proposed quinone channel between LHαβ subunits in the nRC-LH, forming a sealed LH ring that was disrupted by transmembrane helices from cytochrome and subunit X to allow quinone shuttling. dRC-LH lacked subunit X, leading to an exposed LH ring with a larger opening, which together accelerated the quinone exchange rate. We also assigned amino acid sequences of subunit X and two hypothetical proteins Y and Z that functioned in forming the quinone channel and stabilizing the RC-LH interactions. This study reveals the structural basis by which Cars assembly regulates the architecture and quinone exchange of bacterial RC-LH complexes. These findings mark an important step forward in understanding the evolution and diversity of prokaryotic photosynthetic apparatus.

PubMed: 37737710
DOI: 10.7554/eLife.88951

Experimental method

ELECTRON MICROSCOPY (3.1 Å)