| Autor: |
Pu Qian, Nguyen-Phan, Cam T., Gardiner, Alastair T., Croll, Tristan I., Roszak, Aleksander W., Southall, June, Jackson, Philip J., Vasilev, Cvetelin, Castro-Hartmann, Pablo, Sader, Kasim, Hunter, C. Neil, Cogdell, Richard J. |
| Předmět: |
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| Zdroj: |
Proceedings of the National Academy of Sciences of the United States of America; 10/25/2022, Vol. 119 Issue 43, preceding p1-11, 24p |
| Abstrakt: |
The genomes of some purple photosynthetic bacteria contain a multigene puc family encoding a series of a- and ß-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 aß-side chains and the bacteriochlorin rings, further emphasizing the major role that H bonds play in spectral tuning of bacterial antenna complexes. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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