7y7b
Cryo-EM structure of cryptophyte photosystem ICryo-EM structure of cryptophyte photosystem I
Structural highlights
Publication Abstract from PubMedCryptophyte 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-A 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. Structural basis and evolution of the photosystem I-light-harvesting supercomplex of cryptophyte algae.,Zhao LS, Wang P, Li K, Zhang QB, He FY, Li CY, Su HN, Chen XL, Liu LN, Zhang YZ Plant Cell. 2023 Jun 26;35(7):2449-2463. doi: 10.1093/plcell/koad087. PMID:36943796[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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