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The Donor-Acceptor side interactions in Photosystem II
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
(English)Manuscript (preprint) (Other academic)
Keyword [en]
Photosystem II, QA, QB, TyrZ, quinones
National Category
Natural Sciences
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:uu:diva-321124OAI: oai:DiVA.org:uu-321124DiVA: diva2:1092139
Available from: 2017-04-30 Created: 2017-04-30 Last updated: 2017-05-04
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. 72 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1527
Keyword
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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