8K5O

Cryo-EM structure of the RC-LH core comples from Halorhodospira halochloris

This is a non-PDB format compatible entry.

Summary for 8K5O

• Entry DOI: 10.2210/pdb8k5o/pdb
• EMDB information: 36907
• Descriptor: Photosynthetic reaction center cytochrome c subunit, reaction center small polypeptide, reactin center small polypeptide, ... (25 entities in total)
• Functional Keywords: rc-lh complex, halorhodospira halochloris, photosynthesis
• Biological source: Halorhodospira halochloris; More
• Total number of polymer chains: 56
• Total formula weight: 659377.74

Authors

Wang, G.-L.,Qi, C.-H.,Yu, L.-J. (deposition date: 2023-07-22, release date: 2024-05-22, Last modification date: 2024-11-20)

Primary citation

Qi, C.H.,Wang, G.L.,Wang, F.F.,Wang, J.,Wang, X.P.,Zou, M.J.,Ma, F.,Madigan, M.T.,Kimura, Y.,Wang-Otomo, Z.Y.,Yu, L.J.
Structural insights into the unusual core photocomplex from a triply extremophilic purple bacterium, Halorhodospira halochloris.
J Integr Plant Biol, 66:2262-2272, 2024

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 (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.

PubMed: 38411333
DOI: 10.1111/jipb.13628

Experimental method

ELECTRON MICROSCOPY (2.42 Å)