Extended Data Fig. 8: Structural changes at the Cl-1 channel and proton release pathways after 2F.
From: Oxygen-evolving photosystem II structures during S1–S2–S3 transitions
a, Structures of PSII at Cl-1 channels superposed with Fobs(2F) – Fobs(1F) difference densities contoured at +3.0σ (green) and −3.0σ (orange), with delay times from 1 µs to 5 ms. The 1F model is depicted in grey, and intermediate structures of D1, D2, CP43 and PsbO proteins are depicted in yellow, cyan, magenta and orange, respectively. Water molecules at their ground states and intermediate states are depicted in red and cyan spheres, respectively. O6* and O6 are represented by magenta spheres. Black dotted lines represent hydrogen bonds. Black solid lines link the oxo-oxygen in the OEC and the ligand water to the metal ions, as well as ligand residues and water molecules to Cl-1. Black arrows indicate structural changes. Disordered water and residues are encircled by red dotted lines, and ordered water molecules in the intermediate structures are encircled by cyan dotted lines. b, Possible proton release pathways after 2F. Water molecules are depicted as cyan spheres, with their corresponding numbers labelled. Disordered water molecules, Cl-1 and residues are depicted with arched lines, and an orange outer ring around water molecules indicates that they became ordered. The red arrows indicate the movements of residues. The green dotted arrows indicate the movements of protons.
