7pqd | pdb_00007pqd
Cryo-EM structure of the dimeric Rhodobacter sphaeroides RC-LH1 core complex at 2.9 A: the structural basis for dimerisation
Structural highlights
FunctionRCEM_CERS4 The reaction center is a membrane-bound complex that mediates the initial photochemical event in the electron transfer process of photosynthesis. Publication Abstract from PubMedThe dimeric reaction centre light-harvesting 1 (RC-LH1) core complex of Rhodobacter sphaeroides converts absorbed light energy to a charge separation, and then it reduces a quinone electron and proton acceptor to a quinol. The angle between the two monomers imposes a bent configuration on the dimer complex, which exerts a major influence on the curvature of the membrane vesicles, known as chromatophores, where the light-driven photosynthetic reactions take place. To investigate the dimerisation interface between two RC-LH1 monomers, we determined the cryogenic electron microscopy structure of the dimeric complex at 2.9 A resolution. The structure shows that each monomer consists of a central RC partly enclosed by a 14-subunit LH1 ring held in an open state by PufX and protein-Y polypeptides, thus enabling quinones to enter and leave the complex. Two monomers are brought together through N-terminal interactions between PufX polypeptides on the cytoplasmic side of the complex, augmented by two novel transmembrane polypeptides, designated protein-Z, that bind to the outer faces of the two central LH1 beta polypeptides. The precise fit at the dimer interface, enabled by PufX and protein-Z, by C-terminal interactions between opposing LH1 alphabeta subunits, and by a series of interactions with a bound sulfoquinovosyl diacylglycerol lipid, bring together each monomer creating an S-shaped array of 28 bacteriochlorophylls. The seamless join between the two sets of LH1 bacteriochlorophylls provides a path for excitation energy absorbed by one half of the complex to migrate across the dimer interface to the other half. Cryo-EM structure of the dimeric Rhodobacter sphaeroides RC-LH1 core complex at 2.9 A: the structural basis for dimerisation.,Qian P, Croll TI, Hitchcock A, Jackson PJ, Salisbury JH, Castro-Hartmann P, Sader K, Swainsbury DJK, Hunter CN Biochem J. 2021 Nov 12;478(21):3923-3937. doi: 10.1042/BCJ20210696. PMID:34622934[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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