7Y7B

Cryo-EM structure of cryptophyte photosystem I

Summary for 7Y7B

• Entry DOI: 10.2210/pdb7y7b/pdb
• EMDB information: 33659
• Descriptor: ACPI-1, Photosystem I P700 chlorophyll a apoprotein A1, Photosystem I P700 chlorophyll a apoprotein A2, ... (41 entities in total)
• Functional Keywords: cryptophyte, photosystem i, evolution, photosynthesis
• Biological source: Chroomonas placoidea; More
• Total number of polymer chains: 29
• Total formula weight: 975353.07

Authors

Zhao, L.S.,Li, K.,Zhang, Y.Z.,Liu, L.N. (deposition date: 2022-06-22, release date: 2023-04-12, Last modification date: 2024-10-16)

Primary citation

Zhao, L.S.,Wang, P.,Li, K.,Zhang, Q.B.,He, F.Y.,Li, C.Y.,Su, H.N.,Chen, X.L.,Liu, L.N.,Zhang, Y.Z.
Structural basis and evolution of the photosystem I-light-harvesting supercomplex of cryptophyte algae.
Plant Cell, 35:2449-2463, 2023

PubMed 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 crygenic 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, 1 diatom PsaR homolog, and an additional peptide. The PSI core is surrounded by 14 ACPI subunits that form 2 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.

PubMed: 36943796
DOI: 10.1093/plcell/koad087

Experimental method

ELECTRON MICROSCOPY (2.66 Å)