Structural basis and evolution of the photosystem I-light-harvesting supercomplex of cryptophyte algae



Zhao, Long-Sheng, Wang, Peng, Li, Kang, Zhang, Quan-Bao, He, Fei-Yu, Li, Chun-Yang, Su, Hai-Nan, Chen, Xiu-Lan, Liu, Lu-Ning ORCID: 0000-0002-8884-4819 and Zhang, Yu-Zhong
(2023) Structural basis and evolution of the photosystem I-light-harvesting supercomplex of cryptophyte algae. PLANT CELL, 35 (7). pp. 2449-2463.

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Abstract

Cryptophyte plastids originated from a red algal ancestor through secondary endosymbiosis. Cryptophyte photosystem I (PSI) associates with transmembrane alloxanthin-chlorophyll a/c proteins (ACPIs) as light-harvesting complexes (LHCs). Here we report the structure of the photosynthetic PSI-ACPI supercomplex from the cryptophyte Chroomonas placoidea at 2.7-Å resolution obtained by cryo-electron microscopy. Cryptophyte PSI-ACPI represents a unique PSI-LHCI intermediate in the evolution from red algal to diatom PSI-LHCI. The PSI-ACPI supercomplex is composed of a monomeric PSI core containing 14 subunits, 12 of which originated in red algae, one diatom PsaR homolog, and an additional peptide. The PSI core is surrounded by 14 ACPI subunits that form two antenna layers: an inner layer with 11 ACPIs surrounding the PSI core, and an outer layer containing 3 ACPIs. A pigment-binding subunit that is not present in any other previously characterized PSI-LHCI complexes, ACPI-S, mediates the association and energy transfer between the outer and inner ACPIs. The extensive pigment network of PSI-ACPI ensures efficient light harvesting, energy transfer, and dissipation. Overall, the PSI-LHCI structure identified in this study provides a framework for delineating the mechanisms of energy transfer in cryptophyte PSI-LHCI and for understanding the evolution of photosynthesis in the red lineage, which occurred via secondary endosymbiosis.

Item Type: Article
Uncontrolled Keywords: Light-Harvesting Protein Complexes, Chlorophyll A, Photosystem I Protein Complex, Photosynthesis, Energy Transfer, Diatoms
Divisions: Faculty of Health and Life Sciences
Faculty of Health and Life Sciences > Institute of Systems, Molecular and Integrative Biology
Depositing User: Symplectic Admin
Date Deposited: 18 Apr 2023 08:40
Last Modified: 05 Jul 2023 10:37
DOI: 10.1093/plcell/koad087
Open Access URL: https://doi.org/10.1093/plcell/koad087
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3169637