biostudies-literatureTani KMEXT | Japan Society for the Promotion of Science1904https://www.ebi.ac.uk/biostudies/studies/S-EPMC8991256biostudies-literatureUnknown13(1)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.Nature communicationsAsymmetric structure of the native Rhodobacter sphaeroides dimeric LH1-RC complex.PMC8991256JP20H05086JP20H02856Nagashima KVPHall MWang-Otomo ZYKimura YKikuchi RTakahashi AHumbel BMKawamura SKanno RTani KMizoguchi AYu LJMadigan MTfalseAsymmetric structure of the native Rhodobacter sphaeroides dimeric LH1-RC complex.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.2022-01-01T00:00:00Z2022 Apr2026-05-30T15:28:00.421Z2025-04-04T10:02:04.123ZS-EPMC89912563539341310.1038/s41467-022-29453-8