9wd5
Cryo-EM structure of PSI-CpcL
Structural highlights
Publication Abstract from PubMedPhycobilisomes (PBSs) are supramolecular pigment-protein complexes composed of phycobiliproteins and linker proteins, serving as the major light-harvesting complexes that capture and transfer light energy to photosystem II (PSII) and photosystem I (PSI) in cyanobacteria and eukaryotic red algae. In cyanobacteria, a rod-type PBS that does not have a core is specifically connected to PSI by a linker protein CpcL to form a PSI-CpcL-PBS supercomplex. However, the mechanism of CpcL-PBS association to PSI remains unclear. Here, we report the cryoelectron microscopic structures of PSI-CpcL-PBS at 2.98 A and CpcL-PBS at 2.93 A resolution from a cyanobacterium Anabaena sp. PCC 7120, respectively. CpcL-PBS is located on the stromal side of a PSI tetramer and exhibits a structure of three-layered PBS consisting of four linkers (CpcL, CpcC1, CpcC2, PecC) and 18 pairs of phycocyanin alphabeta monomers. The C-terminal transmembrane helix of CpcL inserts to the membrane and interacts with PsaA, PsaB, and PsaM of PSI at an interface I between two PSI monomers, enabling the formation of the PSI-CpcL-PBS supercomplex. The exact structure of protein subunits and arrangement of bilin and chlorophyll pigments are revealed, which provide a structural basis for the assembly of PSI-CpcL-PBS and possible excitation energy transfer pathways from antennas to PSI within this supercomplex, shedding light on the organization and attachment of CpcL-PBS in cyanobacterial thylakoids. Structural insight of a photosystem I-CpcL-phycobilisome supercomplex from a cyanobacterium Anabaena sp. PCC 7120.,Mao Z, Li Z, Li X, Shen L, Kuang T, Wang W, Shen JR, Han G Proc Natl Acad Sci U S A. 2026 Mar 31;123(13):e2530459123. doi: , 10.1073/pnas.2530459123. Epub 2026 Mar 25. PMID:41880560[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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