title: Deformation of chlorin rings in the Photosystem II crystal structure.
abstract: The crystal structure of Photosystem II (PSII) analyzed at a resolution of 1.9 Å revealed deformations of chlorin rings in the chlorophylls for the first time. We investigated the degrees of chlorin ring deformation and factors that contributed to them in the PSII crystal structure, using a normal-coordinate structural decomposition procedure. The out-of-plane distortion of the P(D1) chlorin ring can be described predominantly by a large "doming mode" arising from the axial ligand, D1-His198, as well as the chlorophyll side chains and PSII protein environment. In contrast, the deformation of P(D2) was caused by a "saddling mode" arising from the D2-Trp191 ring and the doming mode arising from D2-His197. Large ruffling modes, which were reported to lower the redox potential in heme proteins, were observed in P(D1) and Chl(D1), but not in P(D2) and Chl(D2). Furthermore, as P(D1) possessed the largest doming mode among the reaction center chlorophylls, the corresponding bacteriochlorophyll P(L) possessed the largest doming mode in bacterial photosynthetic reaction centers. However, the majority of the redox potential shift in the protein environment was determined by the electrostatic environment. The difference in the chlorin ring deformation appears to directly refer to the difference in "the local steric protein environment" rather than the redox potential value in PSII.
authors.affiliation: 202 Building E, 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: Yasufumi
authors.initials: Y
authors.lastname: Umena
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kawakami
authors.forename: Jian-Ren
authors.initials: JR
authors.lastname: Shen
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kamiya
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishikita
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D002734:Chlorophyll / Q000737:chemistry; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D055672:Static Electricity
chemical_list: D001426:Bacterial Proteins; D045332:Photosystem II Protein Complex; D011166:Porphyrins; D002734:Chlorophyll; C006969:chlorin