Indirect evidence for structural changes coupled with Q<sup>−⋅</sup><sub>B</sub> formation in photosystem II

Reifarth, F.; Ренгер, Г.

doi:10.1016/s0014-5793(98)00491-8

Cited by 33 publications

(17 citation statements)

References 24 publications

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“…Interestingly, the transfer step from Q A -• to Q B -• is less affected by temperature decrease, as was found in experiments using samples frozen after preillumination with one saturating laser flash at room temperature (12). The stepwise oxidation of the WOC by the tyrosine Y Z OX is also sensitive † Financial support by Deutsche Forschungsgemeinschaft (SFB 429, TP A1) is gratefully acknowledged.…”

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confidence: 76%

Temperature- and Hydration-Dependent Protein Dynamics in Photosystem II of Green Plants Studied by Quasielastic Neutron Scattering

et al. 2007

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Protein dynamics in hydrated and vacuum-dried photosystem II (PS II) membrane fragments from spinach has been investigated by quasielastic neutron scattering (QENS) in the temperature range between 5 and 300 K. Three distinct temperature ranges can be clearly distinguished by active type(s) of protein dynamics: (A) At low temperatures (T < 120 K), the protein dynamics of both dry and hydrated PS II is characterized by harmonic vibrational motions. (B) In the intermediate temperature range (120 < T < 240 K), the total mean square displacement total slightly deviates from the predicted linear behavior. The QENS data indicate that this deviation, which is virtually independent of the extent of hydration, is due to a partial onset of diffusive protein motions. (C) At temperatures above 240 K, the protein flexibility drastically changes because of the onset of diffusive (large-amplitude) protein motions. This dynamical transition is clearly hydration-dependent since it is strongly suppressed in dry PS II. The thermally activated onset of protein flexibility as monitored by QENS is found to be strictly correlated with the temperature-dependent increase of the electron transport efficiency from Q(A)(-) to QB (Garbers et al. (1998) Biochemistry 37, 11399-11404). Analogously, the freezing of protein mobility by dehydration in dry PS II appears to be responsible for the blockage of Q(A)(-) reoxidation by Q(B) at hydration values lower than 45% r.h. (Kaminskaya et al. (2003) Biochemistry 42, 8119-8132). Similar effects were observed for reactions of the water-oxidizing complex as outlined in the Discussion section.

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confidence: 76%

Temperature- and Hydration-Dependent Protein Dynamics in Photosystem II of Green Plants Studied by Quasielastic Neutron Scattering

et al. 2007

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“…from its freezing-out at cryogenic temperatures (15,16,59,60) and from the driving force-independent kinetics (15)(16)(17)61). The gating concept explains why the experimentally accessible (monophasic) reaction kinetics are slower than predicted by ET theory (62).…”

Section: Discussionmentioning

confidence: 99%

Carboxylate Shifts Steer Interquinone Electron Transfer in Photosynthesis

Chernev

Zaharieva

Dau

et al. 2011

Journal of Biological Chemistry

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Understanding the mechanisms of electron transfer (ET) in photosynthetic reaction centers (RCs) may inspire novel catalysts for sunlight-driven fuel production. The electron exit pathway of type II RCs comprises two quinone molecules working in series and in between a non-heme iron atom with a carboxyl ligand (bicarbonate in photosystem II (PSII), glutamate in bacterial RCs). For decades, the functional role of the iron has remained enigmatic. We tracked the iron site using microsecond-resolution x-ray absorption spectroscopy after laser-flash excitation of PSII. After formation of the reduced primary quinone, Q A ؊ , the x-ray spectral changes revealed a transition (t1 ⁄ 2 ≈ 150 s) from a bidentate to a monodentate coordination of the bicarbonate at the Fe(II) (carboxylate shift), which reverted concomitantly with the slower ET to the secondary quinone Q B . A redox change of the iron during the ET was excluded. Density-functional theory calculations corroborated the carboxylate shift both in PSII and bacterial RCs and disclosed underlying changes in electronic configuration. We propose that the iron-carboxyl complex facilitates the first interquinone ET by optimizing charge distribution and hydrogen bonding within the Q A FeQ B triad for high yield Q B reduction. Formation of a specific priming intermediate by nuclear rearrangements, setting the stage for subsequent ET, may be a common motif in reactions of biological redox cofactors.

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“…The temperature, which enables 50% activity, is higher for ET to Q B than to Q À B in both spinach thylakoids and PSII membrane fragments Reifarth and Renger 1998). Mößbauer spectroscopy Photosynth Res (2007) 94: 183-202 189 studies using 57 Fe labeled NHFe as a probe (Garbers et al 1998) and measurements of quasielastic neutron scattering (QENS) (Kühn et al 2005, Pieper, Hauß, Buchsteiner, Baczyński, Adamiak, Lechner, Renger unpublished results) revealed that the threshold temperature for increased protein flexibility is virtually the same as for the onset of Q À A reoxidation by Q B .…”

Section: Kinetics and Energetics Of Pqh 2 Formationmentioning

confidence: 93%

Photosystem II: Structure and mechanism of the water:plastoquinone oxidoreductase

2007

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This mini-review briefly summarizes our current knowledge on the reaction pattern of light-driven water splitting and the structure of Photosystem II that acts as a water:plastoquinone oxidoreductase. The overall process comprises three types of reaction sequences: (a) light-induced charge separation leading to formation of the radical ion pair P680+*QA(-*) ; (b) reduction of plastoquinone to plastoquinol at the QB site via a two-step reaction sequence with QA(-*) as reductant and (c) oxidative water splitting into O2 and four protons at a manganese-containing catalytic site via a four-step sequence driven by P680+* as oxidant and a redox active tyrosine YZ acting as mediator. Based on recent progress in X-ray diffraction crystallographic structure analysis the array of the cofactors within the protein matrix is discussed in relation to the functional pattern. Special emphasis is paid on the structure of the catalytic sites of PQH2 formation (QB-site) and oxidative water splitting (Mn4OxCa cluster). The energetics and kinetics of the reactions taking place at these sites are presented only in a very concise manner with reference to recent up-to-date reviews. It is illustrated that several questions on the mechanism of oxidative water splitting and the structure of the catalytic sites are far from being satisfactorily answered.

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Indirect evidence for structural changes coupled with Q^−⋅_B formation in photosystem II

Cited by 33 publications

References 24 publications

Temperature- and Hydration-Dependent Protein Dynamics in Photosystem II of Green Plants Studied by Quasielastic Neutron Scattering

Temperature- and Hydration-Dependent Protein Dynamics in Photosystem II of Green Plants Studied by Quasielastic Neutron Scattering

Carboxylate Shifts Steer Interquinone Electron Transfer in Photosynthesis

Photosystem II: Structure and mechanism of the water:plastoquinone oxidoreductase

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Indirect evidence for structural changes coupled with Q−⋅B formation in photosystem II

Cited by 33 publications

References 24 publications

Temperature- and Hydration-Dependent Protein Dynamics in Photosystem II of Green Plants Studied by Quasielastic Neutron Scattering

Temperature- and Hydration-Dependent Protein Dynamics in Photosystem II of Green Plants Studied by Quasielastic Neutron Scattering

Carboxylate Shifts Steer Interquinone Electron Transfer in Photosynthesis

Photosystem II: Structure and mechanism of the water:plastoquinone oxidoreductase

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Indirect evidence for structural changes coupled with Q^−⋅_B formation in photosystem II