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Title: Cryo-EM structure of a Ca2+-bound photosynthetic LH1-RC complex containing multiple αβ-polypeptides. Author: Tani K, Kanno R, Makino Y, Hall M, Takenouchi M, Imanishi M, Yu LJ, Overmann J, Madigan MT, Kimura Y, Mizoguchi A, Humbel BM, Wang-Otomo ZY. Journal: Nat Commun; 2020 Oct 02; 11(1):4955. PubMed ID: 33009385. 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.[Abstract] [Full Text] [Related] [New Search]