title: Highly resolved proton matrix ENDOR of oriented photosystem II membranes in the S2 state.
abstract: Proton matrix ENDOR was performed to investigate the protons close to the manganese cluster in oriented samples of photosystem II (PS II). Eight pairs of ENDOR signals were detected in oriented PS II membranes. At an angle of θ=0° between the membrane normal vector n and the external field H0, five pairs of ENDOR signals were exchangeable in D2O medium and three pairs were not exchangeable in D2O medium. The hyperfine splitting of 3.60MHz at θ=0° increased to 3.80MHz at θ=90°. The non-exchangeable signals with 1.73MHz hyperfine splitting at θ=0°, which were assigned to a proton in an amino acid residue, were not detected at θ=90° in oriented PS II or in non-oriented PS II. Highly resolved spectra show that only limited numbers of protons were detected by CW-ENDOR spectra, although many protons were located near the CaMn4O5 cluster. The detected exchangeable protons were proposed to arise from the protons belonging to the water molecules, labeled W1-W4 in the 1.9Å crystal structure, directly ligated to the CaMn4O5 cluster, and nearby amino-acid residue.
authors.affiliation: Division of Materials Science (Physics), Graduate School of Science, Nagoya University, Furocho, Chikusa, Nagoya 464-8602, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nagashima
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mino
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy; D008345:Manganese / Q000378:metabolism*; D008958:Models, Molecular; D010100:Oxygen / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D011522:Protons; D018724:Spinacia oleracea / Q000378:metabolism*; D014867:Water / Q000378:metabolism
chemical_list: D045332:Photosystem II Protein Complex; D011522:Protons; D014867:Water; D008345:Manganese; D010100:Oxygen
keywords: 2-morpholinoethanesulfonic acid; CW; ENDOR; EPR; FM; MES; Mn-cluster; OEC; Oxygen evolving; PS II; Photosynthesis; Photosystem II; RF; Tyr161 for higher plants (Tyr160 for cyanobacteria) of the D2 subunit in PS II; Tyr161 of the D1 subunit in PS II; Y(D); Y(Z); continuous wave; electron nuclear double resonance; electron paramagnetic resonance; frequency modulation; oxygen-evolving complex; photosystem II; radio frequency