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Cryo-EM structure of the LH1 complex from Roseiflexus castenholzii
Structural highlights
FunctionQ83XD2_9CHLR Antenna complexes are light-harvesting systems, which transfer the excitation energy to the reaction centers.[SAAS:SAAS00885981] Publication Abstract from PubMedPhotosynthetic complexes comprising light-harvesting (LH) and reaction center (RC) components are essential for biological energy conversion in photosynthesis. Assembly of these multi-protein structures is a topic of great interest, and assembly mechanisms appear to reflect the evolutionary diversity of the particular phototrophic organism. Here we constructed a photosynthetic chimera expressing the Roseiflexus castenholzii LH and Rhodospirillum rubrum RC complexes in a photocomplex-deficient Rsp. rubrum mutant, and spectroscopy confirmed LH expression with absorption maxima at 878 and 801 nm. The chimeric strain grew slower phototrophically than wildtype but faster than a strain containing only the RC, indicating partial energy transfer from LH to RC. Cryo-EM structural analysis revealed that the Rfl. castenholzii LH independently assembled into a closed ring of 15 alphabeta heterodimers lacking carotenoids, resulting in a blue-shifted Q(y) transition, while the Rsp. rubrum RC formed a separate complex with an RC:LH ratio of approximately 17:1 instead of a typical 1:1. Structural differences, including the absence of two Rfl. castenholzii-specific small proteins, likely precluded formation of a conjoined LH-RC in the chimeric strain. These results reveal that distinct photocomplex assembly strategies exist in phylogenetically divergent species and underscore the modularity and adaptability of photosynthetic complexes, offering insights for artificial photosystem design. Assembly, selectivity, and compatibility of bacterial photosynthetic complexes from divergent species detected in a chimeric strain.,Wang L, Yan YH, Wang GL, Yue XY, Qi CH, Zou MJ, Wang-Otomo ZY, Madigan MT, Xin Y, Yu LJ Biochim Biophys Acta Bioenerg. 2026 Jan 27;1867(2):149584. doi: , 10.1016/j.bbabio.2026.149584. PMID:41611047[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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