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Updated: Sep 28, 2025

Purification of Active Photosystem I-Light Harvesting Complex I from Plant Tissues
Published on: February 3, 2023
Structural basis for different types of hetero-tetrameric light-harvesting complexes in a diatom PSII-FCPII
Ryo Nagao1, Koji Kato2, Minoru Kumazawa3
1Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan. nagaoryo@okayama-u.ac.jp.
Abstract:
Fucoxanthin chlorophyll (Chl) a/c-binding proteins (FCPs) function as light harvesters in diatoms. The structure of a diatom photosystem II-FCPII (PSII-FCPII) supercomplex have been solved by cryo-electron microscopy (cryo-EM) previously; however, the FCPII subunits that constitute the FCPII tetramers and monomers are not identified individually due to their low resolutions. Here, we report a 2.5 Å resolution structure of the PSII-FCPII supercomplex using cryo-EM. Two types of tetrameric FCPs, S-tetramer, and M-tetramer, are identified as different types of hetero-tetrameric complexes. In addition, three FCP monomers, m1, m2, and m3, are assigned to different gene products of FCP. The present structure also identifies the positions of most Chls c and diadinoxanthins, which form a complicated pigment network. Excitation-energy transfer from FCPII to PSII is revealed by time-resolved fluorescence spectroscopy. These structural and spectroscopic findings provide insights into an assembly model of FCPII and its excitation-energy transfer and quenching processes.
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