Cryo-EM structures of light-harvesting 2 complexes from Rhodopseudomonas palustris reveal the molecular origin of absorption tuning

0565507 - MBÚ 2023 RIV US eng J - Journal Article
Qian, P. - Nguyen-Phan, C. T. - Gardiner, Alastair T. - Croll, T. I. - Roszak, A. W. - Southall, J. - Jackson, P. J. - Vasilev, C. - Castro-Hartmann, P. - Sader, K. - Hunter, C. N. - Cogdell, R. J.
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. Roč. 119, č. 43 (2022), č. článku e2210109119. ISSN 0027-8424. E-ISSN 1091-6490
EU Projects: European Commission(CZ) 854126 - PhotoRedesign
Institutional support: RVO:61388971
Keywords : absorption band turning * cryo-EM * light-harvesting complex * photosynthesis * Rhodopseudomonas palustris
OECD category: Microbiology
Impact factor: 11.1, year: 2022
Method of publishing: Open access
https://www.pnas.org/doi/10.1073/pnas.2210109119

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.
Permanent Link: https://hdl.handle.net/11104/0337040