7ZCU image
Entry Detail
PDB ID:
7ZCU
EMDB ID:
Keywords:
Title:
PucA-LH2 complex from Rps. palustris
Biological Source:
PDB Version:
Deposition Date:
2022-03-28
Release Date:
2022-10-12
Method Details:
Experimental Method:
Resolution:
2.70 Å
Aggregation State:
PARTICLE
Reconstruction Method:
SINGLE PARTICLE
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Light-harvesting protein B-800-850 alpha chain
Chain IDs:A, D (auth: C), F (auth: E), H (auth: G), J (auth: I), L (auth: K), N (auth: M), P (auth: O), R (auth: Q)
Chain Length:59
Number of Molecules:9
Biological Source:Rhodopseudomonas palustris ATCC 17001
Polymer Type:polypeptide(L)
Description:Light-harvesting protein B-800-850 beta chain
Chain IDs:B, E (auth: D), G (auth: F), I (auth: H), K (auth: J), M (auth: L), O (auth: N), Q (auth: P), S (auth: R)
Chain Length:47
Number of Molecules:9
Biological Source:Rhodopseudomonas palustris ATCC 17001
Polymer Type:polypeptide(L)
Description:PucA-LH2-gamma
Chain IDs:C (auth: S)
Chain Length:97
Number of Molecules:1
Biological Source:Rhodopseudomonas palustris ATCC 17001
Modified Residue
Compound ID Chain ID Parent Comp ID Details 2D Image
CXM A MET modified residue
Primary Citation
Cryo-EM structures of light-harvesting 2 complexes from Rhodopseudomonas palustris reveal the molecular origin of absorption tuning.
Proc.Natl.Acad.Sci.USA 119 e2210109119 e2210109119 (2022)
PMID: 36251992 DOI: 10.1073/pnas.2210109119

Abstact

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.

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