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Tyrosine D oxidation and redox equilibrium in Photosystem II
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. (Photosynthesis group)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.ORCID iD: 0000-0002-6218-3039
2017 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, no 6, p. 407-417Article in journal (Refereed) Published
Abstract [en]

Tyrosine ID (Tyr(D)) is an auxiliary redox active tyrosine residue in photosystem II (PSII). The mechanism of Tyr(D) oxidation was investigated by EPR spectroscopy, flash-induced fluorescence decay and thermoluminescence measurements in PSII enriched membranes from spinach. PSII membranes were chemically treated with 3 mM ascorbate and 1 mM diaminodurene and subsequent washing, leading to the complete reduction of Tyr(D). Tyr(D) oxidation kinetics and competing recombination reactions were measured after a single saturating flash in the absence and presence of DCMU (inhibitor of the Q(B)-site) in the pH range of 4.7-8.5. Two kinetic phases of Tyro oxidation were observed by the time resolved EPR spectroscopy the fast phase (msec-sec time range) and the pH dependent slow phase (tens of seconds time range). In the presence of DCMU, Tyr(D) oxidation kinetics was monophasic in the entire pH range, i.e. only the fast kinetics was observed. The results obtained from the fluorescence and thermoluminescence analysis show that when forward electron transport is blocked in the presence of DCMU, the S(2)Q((S) over bar) recombination outcompetes the slow phase of Tyr(D) oxidation by the S-2 state. Modelling of the whole complex of these electron transfer events associated with Tyr(D) oxidation fitted very well with our experimental data. Based on these data, structural information and theoretical considerations we confirm our assignment of the fast and slow oxidation kinetics to two populations of PSII centers with different water positions (proximal and distal) in the Tyr(D) vicinity.

Place, publisher, year, edition, pages
2017. Vol. 1858, no 6, p. 407-417
Keywords [en]
Photosystem II, Electron transfer, Tyrosine D
National Category
Natural Sciences
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:uu:diva-320913DOI: 10.1016/j.bbabio.2017.02.011ISI: 000402349000001PubMedID: 28235460OAI: oai:DiVA.org:uu-320913DiVA, id: diva2:1091551
Funder
Swedish Research Council, 621-2013-5937Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation, 2011.0067Available from: 2017-04-27 Created: 2017-04-27 Last updated: 2017-07-06Bibliographically approved
In thesis
1. Studies of the two redox active tyrosines in Photosystem II
Open this publication in new window or tab >>Studies of the two redox active tyrosines in Photosystem II
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Photosystem II is a unique enzyme which catalyzes light induced water oxidation. This process is driven by highly oxidizing ensemble of four Chl molecules, PD1, PD2, ChlD1 and ChlD2 called, P680. Excitation of one of the Chls in P680 leads to the primary charge separation, P680+Pheo-. Pheo- transfers electrons sequentially to the primary quinone acceptor QA and the secondary quinone acceptor QB. P680+ in turn extracts electrons from Mn4CaO5 cluster, a site for the water oxidation. There are two redox active tyrosines, TyrZ and TyrD, found in PSII. They are symmetrically located on the D1 and D2 central proteins. Only TyrZ acts as intermediate electron carrier between P680 and Mn4CaO5 cluster, while TyrD does not participate in the linear electron flow and stays oxidized under light conditions. Both tyrosines are involved in PCET.

The reduced TyrD undergoes biphasic oxidation with the fast (msec-sec time range) and the slow (tens of seconds time range) kinetic phases. We assign these phases to two populations of PSII centers with proximal or distal water positions. We also suggest that the TyrD oxidation and stability is regulated by the new small lumenal protein subunit, PsbTn. The possible involvement of PsbTn protein in the proton translocation mechanism from TyrD is suggested.

To assess the possible localization of primary cation in P680 the formation of the triplet state of P680 and the oxidation of TyrZ and TyrD were followed under visible and far-red light. We proposed that far-red light induces the cation formation on ChlD1.

Transmembrane interaction between QB and TyrZ has been studied. The different oxidation yield of TyrZ, measured as a S1 split EPR signal was correlated to the conformational change of protein induced by the QB presence at the QB-site. The change is transferred via H-bonds to the corresponding His-residues via helix D of the D1 protein.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 72
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1527
Keywords
Photosystem II, Tyrosine Z and D, proton-coupled electron transfer
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-320916 (URN)978-91-554-9933-4 (ISBN)
Public defence
2017-06-14, Room 2001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2017-06-01 Created: 2017-04-27 Last updated: 2017-06-08

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Ahmadova, NigarHo, FelixStyring, StenbjörnMamedov, Fikret

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