Activating Anions That Replace Cl- in the O2-Evolving Complex of Photosystem II Slow the Kinetics of the Terminal Step in Water Oxidation and Destabilize the S2 and S3 States

Wincencjusz, Hanna; Yocum, Charles F.; Gorkom, Hans J. van

doi:10.1021/bi982295n

Cited by 83 publications

(118 citation statements)

References 27 publications

(48 reference statements)

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“…21 Recent studies have indicated that the presence of Cl is necessary only for the S 2 →S 3 and S 3 →S 0 transitions of the OEC, while the earlier steps of the cycle can proceed in its absence. 48,49 The amplitude and distance changes of Fourier peak III in the S 3 state are less obvious. Peak III appears substantially above the noise level in three of the six S 3 FTs and is readily distinguishable from the noise in two others.…”

Section: Exafs Of the S 3 Statementioning

confidence: 98%

Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

et al. 2000

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The oxygen-evolving complex of Photosystem II in plants and cyanobacteria catalyzes the oxidation of two water molecules to one molecule of dioxygen. A tetranuclear Mn complex is believed to cycle through five intermediate states (S 0 -S 4 ) to couple the four-electron oxidation of water with the one-electron photochemistry occurring at the Photosystem II reaction center. We have used X-ray absorption spectroscopy to study the local structure of the Mn complex and have proposed a model for it, based on studies of the Mn K-edges and the extended X-ray absorption fine structure of the S 1 and S 2 states. The proposed model consists of two di-μ-oxo-bridged binuclear Mn units with Mn-Mn distances of ~2.7 Å that are linked to each other by a mono-μ-oxo bridge with a Mn-Mn separation of ~3.3 Å. The Mn-Mn distances are invariant in the native S 1 and S 2 states. This report describes the application of X-ray absorption spectroscopy to S 3 samples created under physiological conditions with saturating flash illumination. Significant changes are observed in the Mn-Mn distances in the S 3 state compared to the S 1 and the S 2 states. The two 2.7 Å Mn-Mn distances that characterize the di-μ-oxo centers in the S 1 and S 2 states are lengthened to ~2.8 and 3.0 Å in the S 3 state, respectively. The 3.3 Å Mn-Mn and Mn-Ca distances also increase by 0.04-0.2 Å. These changes in Mn-Mn distances are interpreted as consequences of the onset of substrate/water oxidation in the S 3 state. Mn-centered oxidation is evident during the S 0 →S 1 and S 1 →S 2 transitions. We propose that the changes in Mn-Mn distances during the S 2 →S 3 transition are the result of ligand or water oxidation, leading to the Supporting Information Available: E-space S 3 state EXAFS spectrum; the data in k-space and the background that was removed to reduce the low-frequency contributions that show up as peaks at <1 Å in the Fourier transform; and the Fourier isolate of the k-space S 3 spectrum, shown overplotted on the S 3 EXAFS spectrum (PDF). This material is available free of charge via the Internet at http:// pubs.acs.org. NIH Public Access

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Section: Exafs Of the S 3 Statementioning

confidence: 98%

Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

et al. 2000

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“…Additionally, it is possible that chloride depletion perturbs a proton exit pathway (37). Such disruption could give rise to long-lived higher S states (38,39) that may increase the probability of the release of partially oxidized water intermediates. These possibilities are not mutually exclusive.…”

Section: Psii Electron Donor Side Ros Production By Incomplete Water mentioning

confidence: 99%

Amino acid oxidation of the D1 and D2 proteins by oxygen radicals during photoinhibition of Photosystem II

Kale

Hebert

Frankel

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

133

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The Photosystem II reaction center is vulnerable to photoinhibition. The D1 and D2 proteins, lying at the core of the photosystem, are susceptible to oxidative modification by reactive oxygen species that are formed by the photosystem during illumination. Using spin probes and EPR spectroscopy, we have determined that both O 2 . The identification of specific amino acid residues oxidized by reactive oxygen species provides insights into the mechanism of damage to the D1 and D2 proteins under light stress.photosynthesis | Photosystem II | reactive oxygen species | photo inhibition | mass spectrometry P hotosystem II (PSII) functions as a water-plastoquinone oxidoreductase (1, 2) and is a thylakoid membrane pigmentprotein complex present in all oxygenic photosynthetic organisms (cyanobacteria, algae, and higher plants). Current high-resolution structures of thermophilic cyanobacterial PSII (3, 4), and lower resolution structures of the red algal (5) and higher plant photosystems (6), have been critically important in furthering our understanding of the molecular organization of PSII. Structurally, the PSII reaction center core is composed of five proteins: D1, D2, the α-and β-subunits of cytochrome b 559 , and PsbI. These components bind all of the redox-active cofactors of PSII.Excitation energy transfer and electron transport within PSII are unavoidably associated with production of reactive oxygen species (ROS) when the absorption of light by the chlorophyll antenna exceeds the capacity for energy utilization. Many mechanisms for ROS production have been proposed (for reviews, see refs. 7 and 8). Briefly, singlet oxygen ( 1 O 2 ) may be formed by excitation energy transfer from triplet chlorophylls (formed either by the change in orientation of the spin of an excited electron in the PSII antenna complex, or via charge recombination of the primary radical pair 3 [P 680 •+ Pheo •− ]) to O 2 (9, 10). ROS production by electron transport involves either the two-electron oxidation of water or the one-electron reduction of O 2 on the PSII electron donor and acceptor sides, respectively. On the PSII electron donor side, a twoelectron oxidation of water leads to the formation of hydrogen peroxide (H 2 O 2 ), which may be oxidized to the superoxide anion radical (O 2•−

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“…The OEC consists of four manganese ions, one calcium ion (3,4,6,7), and probably one chloride ion (Ref . 8, but see also Ref. 9).…”

mentioning

confidence: 92%

Influence of the Redox Potential of the Primary Quinone Electron Acceptor on Photoinhibition in Photosystem II

Fufezan

Groß

Sjödin

et al. 2007

Journal of Biological Chemistry

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We report the characterization of the effects of the A249S mutation located within the binding pocket of the primary quinone electron acceptor, Q A , in the D2 subunit of photosystem II in Thermosynechococcus elongatus. This mutation shifts the redox potential of Q A by ϳ؊60 mV. This mutant provides an opportunity to test the hypothesis, proposed earlier from herbicide-induced redox effects, that photoinhibition (light-induced damage of the photosynthetic apparatus) is modulated by the potential of Q A . Thus the influence of the redox potential of Q A on photoinhibition was investigated in vivo and in vitro. Compared with the wild-type, the A249S mutant showed an accelerated photoinhibition and an increase in singlet oxygen production. Measurements of thermoluminescence and of the fluorescence yield decay kinetics indicated that the charge-separated state involving Q A was destabilized in the A249S mutant. These findings support the hypothesis that a decrease in the redox potential of Q A causes an increase in singlet oxygen-mediated photoinhibition by favoring the back-reaction route that involves formation of the reaction center chlorophyll triplet. The kinetics of charge recombination are interpreted in terms of a dynamic structural heterogeneity in photosystem II that results in high and low potential forms of Q A . The effect of the A249S mutation seems to reflect a shift in the structural equilibrium favoring the low potential form. Photosystem II (PSII),2 the water/plastoquinone oxidoreductase, uses light energy to extract four electrons from water, producing oxygen (1-4). Each electron is transferred over a chain of redox cofactors to the terminal plastoquinone Q B , which accepts two electrons and two protons (5). The efficiency of PSII in converting light energy into a charge-separated state is remarkably high (5). The univalent photochemistry must interface with the four-electron chemistry occurring at the electron donor side with the two-electron chemistry at the acceptor side. This is achieved by different mechanisms. On the donor side, the so-called oxygen-evolving complex (OEC) accumulates four redox equivalents before it extracts four electrons from two water molecules. Accumulation is necessary, because the energy needed to extract the electrons one by one from water requires more driving force than visible light provides (4). During the catalytic cycle, the OEC exists in different oxidation states. These are designated S 0 , S 1 , S 2 , S 3 , and S 4 , where the subscript indicates the number of accumulated oxidation equivalents. The cycle is completed when the S 4 state performs a 4-electron oxidation of water, with the OEC being returned to the most reduced of the so-called S states, S 0 . The OEC consists of four manganese ions, one calcium ion (3, 4, 6, 7), and probably one chloride ion (Ref .8, but see also Ref. 9).On the electron acceptor side, electron transfer involves two plastoquinones, the primary and secondary quinone acceptors (Q A and Q B ). Although both are plastoquinones, thei...

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Activating Anions That Replace Cl^- in the O₂-Evolving Complex of Photosystem II Slow the Kinetics of the Terminal Step in Water Oxidation and Destabilize the S₂ and S₃ States

Cited by 83 publications

References 27 publications

Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

Amino acid oxidation of the D1 and D2 proteins by oxygen radicals during photoinhibition of Photosystem II

Influence of the Redox Potential of the Primary Quinone Electron Acceptor on Photoinhibition in Photosystem II

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Activating Anions That Replace Cl- in the O2-Evolving Complex of Photosystem II Slow the Kinetics of the Terminal Step in Water Oxidation and Destabilize the S2 and S3 States

Cited by 83 publications

References 27 publications

Structural Change of the Mn Cluster during the S2→S3 State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

Structural Change of the Mn Cluster during the S2→S3 State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

Amino acid oxidation of the D1 and D2 proteins by oxygen radicals during photoinhibition of Photosystem II

Influence of the Redox Potential of the Primary Quinone Electron Acceptor on Photoinhibition in Photosystem II

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Activating Anions That Replace Cl^- in the O₂-Evolving Complex of Photosystem II Slow the Kinetics of the Terminal Step in Water Oxidation and Destabilize the S₂ and S₃ States

Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy