8EQM

Structure of a dimeric photosystem II complex acclimated to far-red light

Summary for 8EQM

• Entry DOI: 10.2210/pdb8eqm/pdb
• EMDB information: 28539
• Descriptor: Photosystem II protein D1, Photosystem II reaction center protein L, Photosystem II reaction center protein M, ... (34 entities in total)
• Functional Keywords: far-red, photosystem ii, cyanobacteria, chlorophyll, photosynthesis
• Biological source: Synechococcus sp. PCC 7335; More
• Total number of polymer chains: 32
• Total formula weight: 702027.75

Authors

Gisriel, C.J.,Shen, G.,Flesher, D.A.,Kurashov, V.,Golbeck, J.H.,Brudvig, G.W.,Amin, M.,Bryant, D.A. (deposition date: 2022-10-08, release date: 2022-12-28, Last modification date: 2023-01-25)

Primary citation

Gisriel, C.J.,Shen, G.,Flesher, D.A.,Kurashov, V.,Golbeck, J.H.,Brudvig, G.W.,Amin, M.,Bryant, D.A.
Structure of a dimeric photosystem II complex from a cyanobacterium acclimated to far-red light.
J.Biol.Chem., 299:102815-102815, 2022

PubMed Abstract: Photosystem II (PSII) is the water-splitting enzyme central to oxygenic photosynthesis. To drive water oxidation, light is harvested by accessory pigments, mostly chlorophyll (Chl) a molecules, which absorb visible light (400-700 nm). Some cyanobacteria facultatively acclimate to shaded environments by altering their photosynthetic machinery to additionally absorb far-red light (FRL, 700-800 nm), a process termed far-red light photoacclimation or FaRLiP. During far-red light photoacclimation, FRL-PSII is assembled with FRL-specific isoforms of the subunits PsbA, PsbB, PsbC, PsbD, and PsbH, and some Chl-binding sites contain Chls d or f instead of the usual Chl a. The structure of an apo-FRL-PSII monomer lacking the FRL-specific PsbH subunit has previously been determined, but visualization of the dimeric complex has remained elusive. Here, we report the cryo-EM structure of a dimeric FRL-PSII complex. The site assignments for Chls d and f are consistent with those assigned in the previous apo-FRL-PSII monomeric structure. All sites that bind Chl d or Chl f at high occupancy exhibit a FRL-specific interaction of the formyl moiety of the Chl d or Chl f with the protein environment, which in some cases involves a phenylalanine sidechain. The structure retains the FRL-specific PsbH2 subunit, which appears to alter the energetic landscape of FRL-PSII, redirecting energy transfer from the phycobiliprotein complex to a Chl f molecule bound by PsbB2 that acts as a bridge for energy transfer to the electron transfer chain. Collectively, these observations extend our previous understanding of the structure-function relationship that allows PSII to function using lower energy FRL.

PubMed: 36549647
DOI: 10.1016/j.jbc.2022.102815

Experimental method

ELECTRON MICROSCOPY (2.6 Å)