title: Short hydrogen bond between redox-active tyrosine Y(Z) and D1-His190 in the photosystem II crystal structure.
abstract: The crystal structure of photosystem II (PSII) analyzed at a resolution of 1.9 Å revealed a remarkably short H-bond between redox-active tyrosine Y(Z) and D1-His190 (2.46 Å donor-acceptor distance). Using large-scale quantum mechanical/molecular mechanical (QM/MM) calculations with the explicit PSII protein environment, we were able to reproduce this remarkably short H-bond in the original geometry of the crystal structure in the neutral [Y(Z)O···H···N(ε)-His-N(δ)H···O═Asn] state, but not in the oxidized states, indicating that the neutral state was the one observed in the crystal structure. In addition to the appropriate redox/protonation state of Y(Z) and D1-His190, we found that the presence of a cluster of water molecules played a key role in shortening the distance between Y(Z) and D1-His190. The orientations of the water molecules in the cluster were energetically stabilized by the highly polarized PSII protein environment, where the Ca ion of the oxygen-evolving complex (OEC) and the OEC ligand D1-Glu189 were also involved.
authors.affiliation: Career-Path Promotion Unit for Young Life Scientists, Graduate School of Medicine, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Saito
authors.forename: Jian-Ren
authors.initials: JR
authors.lastname: Shen
authors.forename: Toyokazu
authors.initials: T
authors.lastname: Ishida
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishikita
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000737:chemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D011522:Protons; D013816:Thermodynamics; D014443:Tyrosine / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D045332:Photosystem II Protein Complex; D011522:Protons; D014867:Water; D014443:Tyrosine