title: Probing tyrosine Z oxidation in Photosystem II core complex isolated from spinach by EPR at liquid helium temperatures.
abstract: Tyrosine Z (Tyr(Z)) oxidation observed at liquid helium temperatures provides new insights into the structure and function of Tyr(Z) in active Photosystem II (PSII). However, it has not been reported in PSII core complex from higher plants. Here, we report Tyr(Z) oxidation in the S(1) and S(2) states in PSII core complex from spinach for the first time. Moreover, we identified a 500 G-wide symmetric EPR signal (peak position g = 2.18, trough position g = 1.85) together with the g = 2.03 signal induced by visible light at 10 K in the S(1) state in the PSII core complex. These two signals decay with a similar rate in the dark and both disappear in the presence of 6% methanol. We tentatively assign this new feature to the hyperfine structure of the S(1)Tyr(Z)(*) EPR signal. Furthermore, EPR signals of the S(2) state of the Mn-cluster, the oxidation of the non-heme iron, and the S(1)Tyr(Z)(*) in PSII core complexes and PSII-enriched membranes from spinach are compared, which clearly indicate that both the donor and acceptor sides of the reaction center are undisturbed after the removal of LHCII. These results suggest that the new spinach PSII core complex is suitable for the electron transfer study of PSII at cryogenic temperatures.
authors.affiliation: Laboratory of Photochemistry, Beijing National Laboratory of Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Ren
authors.forename: Chunxi
authors.initials: C
authors.lastname: Zhang
authors.forename: Han
authors.initials: H
authors.lastname: Bao
authors.forename: Jianren
authors.initials: J
authors.lastname: Shen
authors.forename: Jingquan
authors.initials: J
authors.lastname: Zhao
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D006371:Helium / Q000737:chemistry; D010084:Oxidation-Reduction; D044367:Phase Transition; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D018724:Spinacia oleracea / Q000378:metabolism*; D013696:Temperature; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism*; D014867:Water / Q000378:metabolism
chemical_list: D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D014867:Water; D006371:Helium; D014443:Tyrosine