Structure of cyanobacterial photosystem I complexed with ferredoxin at 1.97 Å resolution

• DOI: 10.1038/s42003-022-03926-4
• Publication Date: 2022-09-12T05:03:38Z
• Authors: Jiannan Li; Noriyuki Hamaoka; Fumiaki Makino; Akihiro Kawamoto; Yuxi Lin; Matthias Rögner; Marc M. Nowaczyk; Young-Ho Lee; Keiichi Namba; Christoph Gerle; Genji Kurisu
• Keywords: Cytochrome f; P700; Cytochrome b6f complex

Abstract Photosystem I (PSI) is a light driven electron pump transferring electrons from Cytochrome c 6 (Cyt ) to Ferredoxin (Fd). An understanding of this transfer process hampered by paucity structural detail concerning PSI:Fd interface and the possible binding sites Cyt . Here we describe high resolution cryo-EM structure Thermosynechococcus elongatus BP-1 PSI in complex with Fd loosely bound Side chain interactions at including bridging water molecules are visualized detail. The explains properties mutants PsaE PsaC that affect kinetics suggests molecular switch for dissociation upon reduction. Calorimetry-based thermodynamic analyses confirms single site demonstrates complexation purely entropy. A reaction cycle efficient via proposed.