8IUN

Cryo-EM structure of the CRT-LESS RC-LH core complex from roseiflexus castenholzii

Summary for 8IUN

• Entry DOI: 10.2210/pdb8iun/pdb
• EMDB information: 35727
• Descriptor: Antenna complex alpha/beta subunit, gamma-Carotene, BACTERIOPHEOPHYTIN A, ... (21 entities in total)
• Functional Keywords: crt-less rc-lh core complex, roseiflexus castenholzii, photosynthesis
• Biological source: Roseiflexus castenholzii; More
• Total number of polymer chains: 36
• Total formula weight: 452413.91

Authors

Wang, G.-L.,Qi, C.-H.,Yu, L.-J. (deposition date: 2023-03-24, release date: 2023-12-06, Last modification date: 2025-09-17)

Primary citation

Qi, C.H.,Wang, G.L.,Wang, F.F.,Xin, Y.,Zou, M.J.,Madigan, M.T.,Wang-Otomo, Z.Y.,Ma, F.,Yu, L.J.
New insights on the photocomplex of Roseiflexus castenholzii revealed from comparisons of native and carotenoid-depleted complexes.
J.Biol.Chem., 299:105057-105057, 2023

PubMed Abstract: In wild-type phototrophic organisms, carotenoids (Crts) are primarily packed into specific pigment-protein complexes along with (Bacterio)chlorophylls and play important roles in the photosynthesis. Diphenylamine (DPA) inhibits carotenogenesis but not phototrophic growth of anoxygenic phototrophs and eliminates virtually all Crts from photocomplexes. To investigate the effect of Crts on assembly of the reaction center-light-harvesting (RC-LH) complex from the filamentous anoxygenic phototroph Roseiflexus (Rfl.) castenholzii, we generated carotenoidless (Crt-less) RC-LH complexes by growing cells in the presence of DPA. Here, we present cryo-EM structures of the Rfl. castenholzii native and Crt-less RC-LH complexes with resolutions of 2.86 Å and 2.85 Å, respectively. From the high-quality map obtained, several important but previously unresolved details in the Rfl. castenholzii RC-LH structure were determined unambiguously including the assignment and likely function of three small polypeptides, and the content and spatial arrangement of Crts with bacteriochlorophyll molecules. The overall structures of Crt-containing and Crt-less complexes are similar. However, structural comparisons showed that only five Crts remain in complexes from DPA-treated cells and that the subunit X (TMx) flanked on the N-terminal helix of the Cyt-subunit is missing. Based on these results, the function of Crts in the assembly of the Rfl. castenholzii RC-LH complex and the molecular mechanism of quinone exchange is discussed. These structural details provide a fresh look at the photosynthetic apparatus of an evolutionary ancient phototroph as well as new insights into the importance of Crts for proper assembly and functioning of the RC-LH complex.

PubMed: 37468106
DOI: 10.1016/j.jbc.2023.105057

Experimental method

ELECTRON MICROSCOPY (2.85 Å)