Cryo-EM structure of the dimeric Rhodobacter sphaeroides RC-LH1 core complex at 2.9Å: The structural basis for dimerisation

Qian, Pu, Croll, Tristan I., Hitchcock, Andrew, Jackson, Philip J., Salisbury, Jack H., Castro-Hartmann, Pablo, Sader, Kasim, Swainsbury, David J. K. and Hunter, C. Neil (2021) Cryo-EM structure of the dimeric Rhodobacter sphaeroides RC-LH1 core complex at 2.9Å: The structural basis for dimerisation. Biochemical Journal, 478 (21). pp. 3923-3937. ISSN 0264-6021

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Abstract

The 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 lightdriven 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 Å 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 β polypeptides. The precise fit at the dimer interface, enabled by PufX and protein-Z, by C-terminal interactions between opposing LH1 αβ 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.

Item Type: Article
Additional Information: Funding Information: P.Q., D.J.K.S. and C.N.H. were supported by the Biotechnology and Biological Sciences Research Council (BBSRC) UK, award number BB/M000265/1, and European Research Council (ERC) Synergy Award 854126. T.I.C. acknowledges Wellcome Trust grant 209407/Z/17/Z. A.H. acknowledges support from a Royal Society University Research Fellowship (award number URF\R1\191548). J.H.S. is supported by a PhD studentship jointly funded by the Royal Society and the ERC.
Uncontrolled Keywords: biochemistry,molecular biology,cell biology ,/dk/atira/pure/subjectarea/asjc/1300/1303
Faculty \ School: Faculty of Science > School of Biological Sciences
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Depositing User: LivePure Connector
Date Deposited: 17 Aug 2022 13:30
Last Modified: 24 Sep 2022 07:03
URI: https://ueaeprints.uea.ac.uk/id/eprint/87385
DOI: 10.1042/BCJ20210696

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