Asymmetric structure of the native Rhodobacter sphaeroides dimeric LH1–RC complex

• Published in: Nature communications Vol. 13; no. 1; pp. 1904 - 9
• Main Authors: Tani, Kazutoshi, Kanno, Ryo, Kikuchi, Riku, Kawamura, Saki, Nagashima, Kenji V. P., Hall, Malgorzata, Takahashi, Ai, Yu, Long-Jiang, Kimura, Yukihiro, Madigan, Michael T., Mizoguchi, Akira, Humbel, Bruno M., Wang-Otomo, Zheng-Yu
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07.04.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 101/28; 631/449/1734; 631/535/1258/1259; 631/57/1464; Assembly; Asymmetric structures; Bacterial Proteins - metabolism; Dimers; Humanities and Social Sciences; Light-Harvesting Protein Complexes - metabolism; Models, Molecular; Monomers; multidisciplinary; N-Terminus; Peptides - chemistry; Photosynthesis; Pigments; Polypeptides; Proteins; Rhodobacter sphaeroides; Rhodobacter sphaeroides - metabolism; Science; Science (multidisciplinary); Structural integrity; Topology
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-29453-8

Rhodobacter sphaeroides is a model organism in bacterial photosynthesis, and its light-harvesting-reaction center (LH1–RC) complex contains both dimeric and monomeric forms. Here we present cryo-EM structures of the native LH1–RC dimer and an LH1–RC monomer lacking protein-U (ΔU). The native dimer reveals several asymmetric features including the arrangement of its two monomeric components, the structural integrity of protein-U, the overall organization of LH1, and rigidities of the proteins and pigments. PufX plays a critical role in connecting the two monomers in a dimer, with one PufX interacting at its N-terminus with another PufX and an LH1 β-polypeptide in the other monomer. One protein-U was only partially resolved in the dimeric structure, signaling different degrees of disorder in the two monomers. The ΔU LH1–RC monomer was half-moon-shaped and contained 11 α- and 10 β-polypeptides, indicating a critical role for protein-U in controlling the number of αβ-subunits required for dimer assembly and stabilization. These features are discussed in relation to membrane topology and an assembly model proposed for the native dimeric complex. Rhodobacter sphaeroides is a model organism for studying bacterial photosynthesis. Here, the authors present structures of its native dimeric and a protein-U-lacking monomeric light-harvesting-reaction center complexes, which reveal asymmetric features for the dimer and an altered shape for the monomer.