7fix
Cryo-EM structure of cyanobacterial photosystem I in the presence of ferredoxin and cytochrome c6Cryo-EM structure of cyanobacterial photosystem I in the presence of ferredoxin and cytochrome c6
Structural highlights
FunctionPSAA_THEVB PsaA and PsaB bind P700, the primary electron donor of photosystem I (PSI), as well as the electron acceptors A0, A1 and FX. PSI is a plastocyanin/cytochrome c6-ferredoxin oxidoreductase, converting photonic excitation into a charge separation, which transfers an electron from the donor P700 chlorophyll pair to the spectroscopically characterized acceptors A0, A1, FX, FA and FB in turn. Oxidized P700 is reduced on the lumenal side of the thylakoid membrane by plastocyanin or cytochrome c6.[1] [2] [3] [4] Publication Abstract from PubMedPhotosystem I (PSI) is a light driven electron pump transferring electrons from Cytochrome c(6) (Cyt c(6)) to Ferredoxin (Fd). An understanding of this electron transfer process is hampered by a paucity of structural detail concerning PSI:Fd interface and the possible binding sites of Cyt c(6). Here we describe the high resolution cryo-EM structure of Thermosynechococcus elongatus BP-1 PSI in complex with Fd and a loosely bound Cyt c(6). Side chain interactions at the PSI:Fd interface including bridging water molecules are visualized in detail. The structure explains the properties of mutants of PsaE and PsaC that affect kinetics of Fd binding and suggests a molecular switch for the dissociation of Fd upon reduction. Calorimetry-based thermodynamic analyses confirms a single binding site for Fd and demonstrates that PSI:Fd complexation is purely driven by entropy. A possible reaction cycle for the efficient transfer of electrons from Cyt c(6) to Fd via PSI is proposed. Structure of cyanobacterial photosystem I complexed with ferredoxin at 1.97 A resolution.,Li J, Hamaoka N, Makino F, Kawamoto A, Lin Y, Rogner M, Nowaczyk MM, Lee YH, Namba K, Gerle C, Kurisu G Commun Biol. 2022 Sep 12;5(1):951. doi: 10.1038/s42003-022-03926-4. PMID:36097054[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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