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  • Title: Structural basis for energy harvesting and dissipation in a diatom PSII-FCPII supercomplex.
    Author: Nagao R, Kato K, Suzuki T, Ifuku K, Uchiyama I, Kashino Y, Dohmae N, Akimoto S, Shen JR, Miyazaki N, Akita F.
    Journal: Nat Plants; 2019 Aug; 5(8):890-901. PubMed ID: 31358960.
    Abstract:
    Light-harvesting antenna systems in photosynthetic organisms harvest solar energy and transfer it to the photosynthetic reaction centres to initiate charge-separation and electron-transfer reactions. Diatoms are one of the important groups of oxyphototrophs and possess fucoxanthin chlorophyll a/c-binding proteins (FCPs) as light harvesters. The organization and association pattern of FCP with the photosystem II (PSII) core are unknown. Here we solved the structure of PSII-FCPII supercomplexes isolated from a diatom, Chaetoceros gracilis, by single-particle cryoelectron microscopy. The PSII-FCPII forms a homodimer. In each monomer, two FCP homotetramers and three FCP monomers are associated with one PSII core. The structure reveals a highly complicated protein-pigment network that is different from the green-type light-harvesting apparatus. Comparing these two systems allows the identification of energy transfer and quenching pathways. These findings provide structural insights into not only excitation-energy transfer mechanisms in the diatom PSII-FCPII, but also changes of light harvesters between the red- and green-lineage oxyphototrophs during evolution.
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