The photosystem I supercomplex from a primordial green alga Ostreococcus tauri harbors three light-harvesting complex trimers
- National Institute for Basic Biology, Japan
- Chinese Academy of Sciences, China
- National Institutes of Natural Sciences, Japan
Abstract
As a ubiquitous picophytoplankton in the ocean and an early-branching green alga, Ostreococcus tauri is a model prasinophyte species for studying the functional evolution of the light-harvesting systems in photosynthesis. Here, we report the structure and function of the O. tauri photosystem I (PSI) supercomplex in low light conditions, where it expands its photon-absorbing capacity by assembling with the light-harvesting complexes I (LHCI) and a prasinophyte-specific light-harvesting complex (Lhcp). The architecture of the supercomplex exhibits hybrid features of the plant-type and the green algal-type PSI supercomplexes, consisting of a PSI core, a Lhca1-Lhca4-Lhca2-Lhca3 belt attached on one side and a Lhca5-Lhca6 heterodimer associated on the other side between PsaG and PsaH. Interestingly, nine Lhcp subunits, including one Lhcp1 monomer with a phosphorylated amino-terminal threonine and eight Lhcp2 monomers, oligomerize into three trimers and associate with PSI on the third side between Lhca6 and PsaK. The Lhcp1 phosphorylation and the light-harvesting capacity of PSI were subjected to reversible photoacclimation, suggesting that the formation of OtPSI-LHCI-Lhcp supercomplex is likely due to a phosphorylation-dependent mechanism induced by changes in light intensity. Notably, this supercomplex did not exhibit far-red peaks in the 77 K fluorescence spectra, which is possibly due to the weak coupling of the chlorophyll a603-a609 pair in OtLhca1-4.
Data availability
The atomic coordinates of the OtPSI-LHCI-Lhcp supercomplex have been deposited in the Protein Data Bank (PDB) with accession code 7YCA. The cryo-EM map of the supercomplex has been deposited in the Electron Microscopy Data Bank (EMDB) with accession code EMD-33737. The local maps and corresponding models of the three individual Lhcp trimers have also been deposited in the EMDB and PDB under accession codes of EMD-34733 and 8HG3, EMD-34735 and 8HG5, EMD-34736 and 8HG6.
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Cryo-EM structure of the Lhcp complex from Ostreococcus tauriProtein Data Bank, 8HG3.
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Cryo-EM structure of the PSI-LHCI-Lhcp supercomplex from Ostreococcus tauriElectron Microscopy Data Bank, EMD-33737.
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Cryo-EM structure of the Lhcp complex from Ostreococcus tauriElectron Microscopy Data Bank, EMD-34733.
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Cryo-EM structure of the prasinophyte-specific light-harvesting complex (Lhcp)from Ostreococcus tauriElectron Microscopy Data Bank, EMD-34735.
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Cryo-EM structure of the prasinophyte-specific light-harvesting complex (Lhcp)from Ostreococcus tauriElectron Microscopy Data Bank, EMD-34736.
Article and author information
Author details
Funding
Japan Society for the Promotion of Science (21H04778)
- Jun Minagawa
Japan Society for the Promotion of Science (21H05040)
- Jun Minagawa
National Natural Science Foundation of China (31925024)
- Zhenfeng Liu
Chinese Academy of Sciences (XDB37020101)
- Zhenfeng Liu
Chinese Academy of Sciences (YSBR-015)
- Zhenfeng Liu
National Key Research and Development Program of China (2017YFA0503702)
- Zhenfeng Liu
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2023, Ishii et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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The photosystem I supercomplex from a primordial green alga Ostreococcus tauri harbors three light-harvesting complex trimers
eLife 12:e84488.
https://doi.org/10.7554/eLife.84488
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