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Cryo-EM structure of a Ca2+-bound photosynthetic LH1-RC complex containing multiple αβ-polypeptides

Authors :
Zheng-Yu Wang-Otomo
Kazutoshi Tani
Malgorzata Hall
Yuki Makino
Ryo Kanno
Bruno M. Humbel
Yukihiro Kimura
Mizuki Takenouchi
Long-Jiang Yu
Akira Mizoguchi
Michael T. Madigan
Jörg Overmann
Michie Imanishi
Source :
Nature Communications, Nature Communications, Vol 11, Iss 1, Pp 1-9 (2020)
Publication Year :
2020
Publisher :
Springer Science and Business Media LLC, 2020.

Abstract

The light-harvesting-reaction center complex (LH1-RC) from the purple phototrophic bacterium Thiorhodovibrio strain 970 exhibits an LH1 absorption maximum at 960 nm, the most red-shifted absorption for any bacteriochlorophyll (BChl) a-containing species. Here we present a cryo-EM structure of the strain 970 LH1-RC complex at 2.82 Å resolution. The LH1 forms a closed ring structure composed of sixteen pairs of the αβ-polypeptides. Sixteen Ca ions are present in the LH1 C-terminal domain and are coordinated by residues from the αβ-polypeptides that are hydrogen-bonded to BChl a. The Ca2+-facilitated hydrogen-bonding network forms the structural basis of the unusual LH1 redshift. The structure also revealed the arrangement of multiple forms of α- and β-polypeptides in an individual LH1 ring. Such organization indicates a mechanism of interplay between the expression and assembly of the LH1 complex that is regulated through interactions with the RC subunits inside.<br />Here the authors report a cryo-EM structure of the light-harvesting-reaction center complex (LH1- RC) from the purple phototrophic bacterium Thiorhodovibrio strain 970, providing insights into the mechanisms that underlie the absorbance properties of both the LH1 and the RC of this spectrally unusual purple bacterium.

Details

ISSN :
20411723
Volume :
11
Database :
OpenAIRE
Journal :
Nature Communications
Accession number :
edsair.doi.dedup.....825acbd50667874db73455c1dfb501f3