Qian, P. et al. (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 of the United States of America, 117(43), e221010911. (doi: 10.1073/pnas.2210109119) (PMID:36251992) (PMCID:PMC9618040)
![[img]](https://eprints.gla.ac.uk/style/images/fileicons/text.png) |
Text
278884.pdf - Published Version Available under License Creative Commons Attribution. 2MB |
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.
| Item Type: | Articles |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Cogdell, Professor Richard and Southall, Mrs June and Gardiner, Dr Alastair and Nguyen Phan, Cam Tu and Roszak, Dr Aleksander |
| Authors: | Qian, P., Nguyen-Phan, T. C., Gardiner, A. T., Croll, T. I., Roszak, A. P., Southall, J., Jackson, P. J., Vasilev, C., Castro-Hartmann, P., Sader, K., Hunter, C. N., and Cogdell, R. J. |
| College/School: | College of Medical Veterinary and Life Sciences > School of Infection & Immunity College of Medical Veterinary and Life Sciences > School of Molecular Biosciences |
| Journal Name: | Proceedings of the National Academy of Sciences of the United States of America |
| Publisher: | National Academy of Sciences |
| ISSN: | 0027-8424 |
| ISSN (Online): | 1091-6490 |
| Published Online: | 17 October 2022 |
| Copyright Holders: | Copyright © 2022 The Author(s) |
| First Published: | First published in Proceedings of the National Academy of Sciences of the United States of America 117(43):e221010911 |
| Publisher Policy: | Reproduced under a Creative Commons license |
University Staff: Request a correction | Enlighten Editors: Update this record
Funder and Project Information
Funder and Project Information