Download MendeleyStructural basis and evolution of the photosystem I-light-harvesting supercomplex of cryptophyte algae.
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.(2023) Plant Cell 35: 2449-2463
- PubMed: 36943796
- DOI: https://doi.org/10.1093/plcell/koad087
- Primary Citation of Related Structures:
7Y7B, 7Y8A - 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.
Organizational Affiliation:
State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China.
