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Title | Structural insights into the unusual core photocomplex from a triply extremophilic purple bacterium, Halorhodospira halochloris. |
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Journal, issue, pages | J Integr Plant Biol, Vol. 66, Issue 10, Page 2262-2272, Year 2024 |
Publish date | Feb 27, 2024 |
Authors | Chen-Hui Qi / Guang-Lei Wang / Fang-Fang Wang / Jie Wang / Xiang-Ping Wang / Mei-Juan Zou / Fei Ma / Michael T Madigan / Yukihiro Kimura / Zheng-Yu Wang-Otomo / Long-Jiang Yu / |
PubMed Abstract | Halorhodospira (Hlr.) halochloris is a triply extremophilic phototrophic purple sulfur bacterium, as it is thermophilic, alkaliphilic, and extremely halophilic. The light-harvesting-reaction center ...Halorhodospira (Hlr.) halochloris is a triply extremophilic phototrophic purple sulfur bacterium, as it is thermophilic, alkaliphilic, and extremely halophilic. The light-harvesting-reaction center (LH1-RC) core complex of this bacterium displays an LH1-Q transition at 1,016 nm, which is the lowest-energy wavelength absorption among all known phototrophs. Here we report the cryo-EM structure of the LH1-RC at 2.42 Å resolution. The LH1 complex forms a tricyclic ring structure composed of 16 αβγ-polypeptides and one αβ-heterodimer around the RC. From the cryo-EM density map, two previously unrecognized integral membrane proteins, referred to as protein G and protein Q, were identified. Both of these proteins are single transmembrane-spanning helices located between the LH1 ring and the RC L-subunit and are absent from the LH1-RC complexes of all other purple bacteria of which the structures have been determined so far. Besides bacteriochlorophyll b molecules (B1020) located on the periplasmic side of the Hlr. halochloris membrane, there are also two arrays of bacteriochlorophyll b molecules (B800 and B820) located on the cytoplasmic side. Only a single copy of a carotenoid (lycopene) was resolved in the Hlr. halochloris LH1-α3β3 and this was positioned within the complex. The potential quinone channel should be the space between the LH1-α3β3 that accommodates the single lycopene but does not contain a γ-polypeptide, B800 and B820. Our results provide a structural explanation for the unusual Q red shift and carotenoid absorption in the Hlr. halochloris spectrum and reveal new insights into photosynthetic mechanisms employed by a species that thrives under the harshest conditions of any phototrophic microorganism known. |
External links | J Integr Plant Biol / PubMed:38411333 |
Methods | EM (single particle) |
Resolution | 2.42 Å |
Structure data | EMDB-36907, PDB-8k5o: |
Chemicals | ChemComp-HEC: ChemComp-PGV: ChemComp-LHG:
PDB-1lzm: Unknown entry PDB-1lzp: ChemComp-UQ8:
ChemComp-UNL: ChemComp-FE: ChemComp-MQ8: ChemComp-CDL: ChemComp-LYC: PDB-1lzq: ChemComp-PEF: ChemComp-BGL: |
Source |
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Keywords | PHOTOSYNTHESIS / RC-LH complex / HALORHODOSPIRA HALOCHLORIS |