Qian, P., Nguyen-Phan, C.T., Gardiner, A.T. et al. (9 more authors) (2022) Cryo-EM structures of light-harvesting 2 complexes from Rhodopseudomonas palustris reveal the molecular origin of absorption tuning. Proceedings of the National Academy of Sciences, 119 (43). e2210109119. ISSN 0027-8424
Abstract
The genomes of some purple photosynthetic bacteria contain a multigene puc family encoding a series of α- and β-polypeptides that together form a heterogeneous antenna of light-harvesting 2 (LH2) complexes. To unravel this complexity, we generated four sets of puc deletion mutants in Rhodopseudomonas palustris, each encoding a single type of pucBA gene pair and enabling the purification of complexes designated as PucA-LH2, PucB-LH2, PucD-LH2, and PucE-LH2. The structures of all four purified LH2 complexes were determined by cryogenic electron microscopy (cryo-EM) at resolutions ranging from 2.7 to 3.6 Å. Uniquely, each of these complexes contains a hitherto unknown polypeptide, γ, that forms an extended undulating ribbon that lies in the plane of the membrane and that encloses six of the nine LH2 αβ-subunits. The γ-subunit, which is located near to the cytoplasmic side of the complex, breaks the C9 symmetry of the LH2 complex and binds six extra bacteriochlorophylls (BChls) that enhance the 800-nm absorption of each complex. The structures show that all four complexes have two complete rings of BChls, conferring absorption bands centered at 800 and 850 nm on the PucA-LH2, PucB-LH2, and PucE-LH2 complexes, but, unusually, the PucD-LH2 antenna has only a single strong near-infared (NIR) absorption peak at 803 nm. Comparison of the cryo-EM structures of these LH2 complexes reveals altered patterns of hydrogen bonds between LH2 αβ-side chains and the bacteriochlorin rings, further emphasizing the major role that H bonds play in spectral tuning of bacterial antenna complexes.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2022 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY) (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
Keywords: | PHOTOSYNTHESIS; RHODOPSEUDOMONAS PALUSTRIS; LIGHT-HARVESTING COMPLEX; CRYO-EM; ABSORPTION BAND TURNING |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Biosciences (Sheffield) > Department of Biomedical Science (Sheffield) |
Funding Information: | Funder Grant number US DEPARTMENT OF ENERGY DE-SC0001035 ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL EP/S002103/1 EUROPEAN COMMISSION - HORIZON 2020 854126 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 22 Nov 2022 11:16 |
Last Modified: | 22 Nov 2022 11:16 |
Status: | Published |
Publisher: | Proceedings of the National Academy of Sciences |
Refereed: | Yes |
Identification Number: | 10.1073/pnas.2210109119 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:193640 |