AI Article Synopsis
- Researchers investigated the structure of the photochemical reaction center (RC) and light-harvesting complex 1 (LH1) in purple photosynthetic bacteria, focusing on Rhodobacter capsulatus.
- They used cryoelectron microscopy to reveal that Rba. capsulatus forms monomeric RC-LH1 complexes with a 15-subunit LH1 ring, where the incorporation of a protein called PufX creates a significant opening.
- The study found that each LH1 subunit has two carotenoids and two bacteriochlorophylls, and through comparisons with other Rhodobacter species, they identified key residues that play a role in the dimerization of the RC-LH1 complex.
Article Abstract
In purple photosynthetic bacteria, the photochemical reaction center (RC) and light-harvesting complex 1 (LH1) assemble to form monomeric or dimeric RC-LH1 membrane complexes, essential for bacterial photosynthesis. Here, we report a 2.59-Å resolution cryoelectron microscopy (cryo-EM) structure of the RC-LH1 supercomplex from Rhodobacter capsulatus. We show that Rba. capsulatus RC-LH1 complexes are exclusively monomers in which the RC is surrounded by a 15-subunit LH1 ring. Incorporation of a transmembrane polypeptide PufX leads to a large opening within the LH1 ring. Each LH1 subunit associates two carotenoids and two bacteriochlorophylls, which is similar to Rba. sphaeroides RC-LH1 but more than one carotenoid per LH1 in Rba. veldkampii RC-LH1 monomer. Collectively, the unique Rba. capsulatus RC-LH1-PufX represents an intermediate structure between Rba. sphaeroides and Rba. veldkampii RC-LH1-PufX. Comparison of PufX from the three Rhodobacter species indicates the important residues involved in dimerization of RC-LH1.
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| http://dx.doi.org/10.1016/j.str.2023.01.006 | DOI Listing |
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