PufX organizes the photosynthetic reaction centre-light harvesting complex 1 (RC-LH1) core complex of Rhodobacter sphaeroides and facilitates quinol/quinone exchange between the RC and cytochrome bc(1) complexes. The structure of PufX in organic solvent reveals two hydrophobic helices flanked by unstructured termini and connected by a helical bend. The proposed location of basic residues and tryptophans at the membrane interface orients the C-terminal helix along the membrane normal, with the GXXXG motifs in positions unsuitable as direct drivers of dimerisation of the RC-LH1 complex. The N-terminal helix is predicted to extend approximately 40 Anggstrom along the membrane interface.
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Architectures of photosynthetic RC-LH1 supercomplexes from .
Sci Adv
October 2024
MOE Key Laboratory of Evolution and Marine Biodiversity, Frontiers Science Center for Deep Ocean Multispheres and Earth System & College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China.
The reaction center-light-harvesting complex 1 (RC-LH1) plays an essential role in the primary reactions of bacterial photosynthesis. Here, we present high-resolution structures of native monomeric and dimeric RC-LH1 supercomplexes from () using cryo-electron microscopy. The RC-LH1 monomer is composed of an RC encircled by an open LH1 ring comprising 15 αβ heterodimers and a PufX transmembrane polypeptide.
View Article and Find Full Text PDFMonitoring molecular events during photo-driven ubiquinone pool reduction in PufX and PufX membranes from Rhobobacter capsulatus by time-resolved FTIR difference spectroscopy.
Plant Physiol Biochem
November 2024
Department of Microbiology & Immunology, University of British Columbia, Vancouver, Canada. Electronic address:
Article Synopsis
- The PufX protein helps certain purple bacteria with the process of exchanging two important molecules, ubiquinol and ubiquinone, in their reaction centers where they convert light into energy.
- Scientists studied this process in a type of purple bacteria called Rhodobacter capsulatus, using a special technique to see what happens when the bacteria were illuminated with light.
- They found that in bacteria without the PufX protein, the reactions weren’t as efficient, meaning that the way the molecule structure was set up made it harder for the needed molecules to reach where they needed to be in the reaction center.
Sulfoquinovosyl diacylglycerol is required for dimerisation of the Rhodobacter sphaeroides reaction centre-light harvesting 1 core complex.
Biochem J
July 2024
School of Biological Sciences, University of East Anglia, Norwich, U.K.
The reaction centre-light harvesting 1 (RC-LH1) core complex is indispensable for anoxygenic photosynthesis. In the purple bacterium Rhodobacter (Rba.) sphaeroides RC-LH1 is produced both as a monomer, in which 14 LH1 subunits form a C-shaped antenna around 1 RC, and as a dimer, where 28 LH1 subunits form an S-shaped antenna surrounding 2 RCs.
View Article and Find Full Text PDFRhodobacter capsulatus forms a compact crescent-shaped LH1-RC photocomplex.
Nat Commun
February 2023
Faculty of Science, Ibaraki University, Mito, Japan.
Article Synopsis
- Rhodobacter capsulatus is a key model organism for studying bacterial photosynthesis, notable for its unique structural components like PufX, which aids in the formation of the light-harvesting 1-reaction center (LH1-RC) complex.
- The cryo-EM structure of its LH1-RC reveals a compact configuration with only 10 αβ-subunits, indicating some differences compared to its relative Rba. sphaeroides, which has additional subunits due to the presence of protein-U.
- PufX in Rba. capsulatus has an unusual conformation that hinders its interaction with other proteins, essential for understanding the formation and function of the LH1-RC in the context of energy
Cryo-EM structure of a monomeric RC-LH1-PufX supercomplex with high-carotenoid content from Rhodobacter capsulatus.
Structure
March 2023
Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK; College of Marine Life Sciences and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China. Electronic address:
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.
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