8WDU

Photosynthetic LH1-RC complex from the purple sulfur bacterium Allochromatium vinosum purified by sucrose density

Summary for 8WDU

• Entry DOI: 10.2210/pdb8wdu/pdb
• EMDB information: 37465
• Descriptor: Photosynthetic reaction center cytochrome c subunit, PROTOPORPHYRIN IX CONTAINING FE, MAGNESIUM ION, ... (25 entities in total)
• Functional Keywords: photosynthesis
• Biological source: Allochromatium vinosum DSM 180; More
• Total number of polymer chains: 36
• Total formula weight: 398715.19

Authors

Tani, K.,Kanno, R.,Harada, A.,Kobayashi, A.,Minamino, A.,Nakamura, N.,Ji, X.-C.,Purba, E.R.,Hall, M.,Yu, L.-J.,Madigan, M.T.,Mizoguchi, A.,Iwasaki, K.,Humbel, B.M.,Kimura, Y.,Wang-Otomo, Z.-Y. (deposition date: 2023-09-16, release date: 2024-02-21, Last modification date: 2024-11-13)

Primary citation

Tani, K.,Kanno, R.,Harada, A.,Kobayashi, Y.,Minamino, A.,Takenaka, S.,Nakamura, N.,Ji, X.C.,Purba, E.R.,Hall, M.,Yu, L.J.,Madigan, M.T.,Mizoguchi, A.,Iwasaki, K.,Humbel, B.M.,Kimura, Y.,Wang-Otomo, Z.Y.
High-resolution structure and biochemical properties of the LH1-RC photocomplex from the model purple sulfur bacterium, Allochromatium vinosum.
Commun Biol, 7:176-176, 2024

PubMed Abstract: The mesophilic purple sulfur phototrophic bacterium Allochromatium (Alc.) vinosum (bacterial family Chromatiaceae) has been a favored model for studies of bacterial photosynthesis and sulfur metabolism, and its core light-harvesting (LH1) complex has been a focus of numerous studies of photosynthetic light reactions. However, despite intense efforts, no high-resolution structure and thorough biochemical analysis of the Alc. vinosum LH1 complex have been reported. Here we present cryo-EM structures of the Alc. vinosum LH1 complex associated with reaction center (RC) at 2.24 Å resolution. The overall structure of the Alc. vinosum LH1 resembles that of its moderately thermophilic relative Alc. tepidum in that it contains multiple pigment-binding α- and β-polypeptides. Unexpectedly, however, six Ca ions were identified in the Alc. vinosum LH1 bound to certain α1/β1- or α1/β3-polypeptides through a different Ca-binding motif from that seen in Alc. tepidum and other Chromatiaceae that contain Ca-bound LH1 complexes. Two water molecules were identified as additional Ca-coordinating ligands. Based on these results, we reexamined biochemical and spectroscopic properties of the Alc. vinosum LH1-RC. While modest but distinct effects of Ca were detected in the absorption spectrum of the Alc. vinosum LH1 complex, a marked decrease in thermostability of its LH1-RC complex was observed upon removal of Ca. The presence of Ca in the photocomplex of Alc. vinosum suggests that Ca-binding to LH1 complexes may be a common adaptation in species of Chromatiaceae for conferring spectral and thermal flexibility on this key component of their photosynthetic machinery.

PubMed: 38347078
DOI: 10.1038/s42003-024-05863-w

Experimental method

ELECTRON MICROSCOPY (2.24 Å)