ジャーナル: Structure / 年: 2025 タイトル: Cryo-EM structures of photocomplexes from the free-living aerobic anoxygenic phototrophic bacterium Erythrobacter sanguineus. 著者: Xing-Yu Yue / Guang-Lei Wang / Mei-Juan Zou / Fei Ma / Zheng-Yu Wang-Otomo / Michael T Madigan / Long-Jiang Yu / 要旨: Aerobic anoxygenic phototrophic bacteria (AAPB) are widely distributed in nature and they are important members of the marine phototrophic community. However, a structural and functional ...Aerobic anoxygenic phototrophic bacteria (AAPB) are widely distributed in nature and they are important members of the marine phototrophic community. However, a structural and functional understanding of the AAPB photosynthetic apparatus is still lacking. Here, we present cryo-EM structures of the LH1-RC (core) and LH2 (peripheral) photocomplexes from the model aerobic phototroph Erythrobacter (Ery.) sanguineus. The LH1 αβ-heterodimers bind the carotenoids bacteriorubixanthinal and caloxanthin-pigments that are absent from anaerobic anoxygenic phototrophs-to form a closed ring structure. Ery. sanguineus LH1-RC contains a lipid-anchored polypeptide unrelated to any of the auxiliary proteins identified in the core complexes of purple bacteria so far. The Ery. sanguineus LH2 complex shows unique absorption characteristics, with its Q transition being blue-shifted to 814 nm. This work provides structural insights into the unusual photosynthetic properties of AAPB and points to new avenues to further explore their biology.