8TO2

Bottom cylinder of high-resolution phycobilisome quenched by OCP (local refinement)

Summary for 8TO2

• Entry DOI: 10.2210/pdb8to2/pdb
• EMDB information: 41434
• Descriptor: Phycobiliprotein ApcE, PHYCOCYANOBILIN, beta,beta-carotene-4,4'-dione, ... (11 entities in total)
• Functional Keywords: complex, light harvesting, pigment, photosynthesis
• Biological source: Synechocystis sp. PCC 6803; More
• Total number of polymer chains: 29
• Total formula weight: 607989.42

Authors

Sauer, P.V.,Sutter, M.,Cupellini, L. (deposition date: 2023-08-02, release date: 2024-04-17, Last modification date: 2024-10-09)

Primary citation

Sauer, P.V.,Cupellini, L.,Sutter, M.,Bondanza, M.,Dominguez Martin, M.A.,Kirst, H.,Bina, D.,Koh, A.F.,Kotecha, A.,Greber, B.J.,Nogales, E.,Polivka, T.,Mennucci, B.,Kerfeld, C.A.
Structural and quantum chemical basis for OCP-mediated quenching of phycobilisomes.
Sci Adv, 10:eadk7535-eadk7535, 2024

PubMed Abstract: Cyanobacteria use large antenna complexes called phycobilisomes (PBSs) for light harvesting. However, intense light triggers non-photochemical quenching, where the orange carotenoid protein (OCP) binds to PBS, dissipating excess energy as heat. The mechanism of efficiently transferring energy from phycocyanobilins in PBS to canthaxanthin in OCP remains insufficiently understood. Using cryo-electron microscopy, we unveiled the OCP-PBS complex structure at 1.6- to 2.1-angstrom resolution, showcasing its inherent flexibility. Using multiscale quantum chemistry, we disclosed the quenching mechanism. Identifying key protein residues, we clarified how canthaxanthin's transition dipole moment in its lowest-energy dark state becomes large enough for efficient energy transfer from phycocyanobilins. Our energy transfer model offers a detailed understanding of the atomic determinants of light harvesting regulation and antenna architecture in cyanobacteria.

PubMed: 38578996
DOI: 10.1126/sciadv.adk7535

Experimental method

ELECTRON MICROSCOPY (2 Å)