%0 Journal Article
%T Structure of cryptophyte photosystem II-light-harvesting antennae supercomplex.
%A Zhang YZ
%A Li K
%A Qin BY
%A Guo JP
%A Zhang QB
%A Zhao DL
%A Chen XL
%A Gao J
%A Liu LN
%A Zhao LS
%J Nat Commun
%V 15
%N 1
%D 2024 Jun 12
%M 38866834
%F 17.694
%R 10.1038/s41467-024-49453-0
%X Cryptophytes are ancestral photosynthetic organisms evolved from red algae through secondary endosymbiosis. They have developed alloxanthin-chlorophyll a/c2-binding proteins (ACPs) as light-harvesting complexes (LHCs). The distinctive properties of cryptophytes contribute to efficient oxygenic photosynthesis and underscore the evolutionary relationships of red-lineage plastids. Here we present the cryo-electron microscopy structure of the Photosystem II (PSII)-ACPII supercomplex from the cryptophyte Chroomonas placoidea. The structure includes a PSII dimer and twelve ACPII monomers forming four linear trimers. These trimers structurally resemble red algae LHCs and cryptophyte ACPI trimers that associate with Photosystem I (PSI), suggesting their close evolutionary links. We also determine a Chl a-binding subunit, Psb-γ, essential for stabilizing PSII-ACPII association. Furthermore, computational calculation provides insights into the excitation energy transfer pathways. Our study lays a solid structural foundation for understanding the light-energy capture and transfer in cryptophyte PSII-ACPII, evolutionary variations in PSII-LHCII, and the origin of red-lineage LHCIIs.