Molecular Structure of the S<sub>2</sub> State with a <i>g</i> = 5 Signal in the Oxygen Evolving Complex of Photosystem II

Taguchi, Shota; Noguchi, Takumi; Mino, Hiroyuki

doi:10.1021/acs.jpcb.0c02913

Cited by 20 publications

(39 citation statements)

References 31 publications

(133 reference statements)

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“…[16][17][18] The Mn III ion in any given isomer has a formally available site for water coordination in the S 3 state. The isomer on the left with the + III ion at Mn1 (S 2 A ) gives rise to the multiline g = 2 (S = 1/2) EPR signal, whereas the one on the right with the + III ion at Mn4 [19,20] (S 2 B ) gives rise to low-field g ! 4 (S !…”

Section: Resultsmentioning

confidence: 99%

Arrested Substrate Binding Resolves Catalytic Intermediates in Higher‐Plant Water Oxidation

et al. 2020

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Among the intermediate catalytic steps of the wateroxidizing Mn 4 CaO 5 cluster of photosystem II (PSII), the final metastable S 3 state is critically important because it binds one substrate and precedes O 2 evolution. Herein, we combine Xand Q-band EPR experiments on native and methanol-treated PSII of Spinacia oleracea and show that methanol-treated PSII preparations of the S 3 state correspond to a previously uncharacterized high-spin (S = 6) species. This is confirmed as a major component also in intact photosynthetic membranes, coexisting with the previously known intermediate-spin conformation (S = 3). The high-spin intermediate is assigned to a water-unbound form, with a Mn IV 3 subunit interacting ferromagnetically via anisotropic exchange with a coordinatively unsaturated Mn IV ion. These results resolve and define the structural heterogeneity of the S 3 state, providing constraints on the S 3 to S 4 transition, on substrate identity and delivery pathways, and on the mechanism of OÀO bond formation.

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Section: Resultsmentioning

confidence: 99%

Arrested Substrate Binding Resolves Catalytic Intermediates in Higher‐Plant Water Oxidation

et al. 2020

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“…[16][17][18] The Mn III ion in any given isomer has af ormally available site for water coordination in the S 3 state. The isomer on the left with the + III ion at Mn1 (S 2 A )g ives rise to the multiline g = 2( S = 1/2) EPR signal, whereas the one on the right with the + III ion at Mn4 [19,20] (S 2 B )g ives rise to low-field g ! 4( S !…”

Section: Resultsmentioning

confidence: 99%

Arrested Substrate Binding Resolves Catalytic Intermediates in Higher‐Plant Water Oxidation

et al. 2020

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Among the intermediate catalytic steps of the water‐oxidizing Mn4CaO5 cluster of photosystem II (PSII), the final metastable S3 state is critically important because it binds one substrate and precedes O2 evolution. Herein, we combine X‐ and Q‐band EPR experiments on native and methanol‐treated PSII of Spinacia oleracea and show that methanol‐treated PSII preparations of the S3 state correspond to a previously uncharacterized high‐spin (S=6) species. This is confirmed as a major component also in intact photosynthetic membranes, coexisting with the previously known intermediate‐spin conformation (S=3). The high‐spin intermediate is assigned to a water‐unbound form, with a MnIV3 subunit interacting ferromagnetically via anisotropic exchange with a coordinatively unsaturated MnIV ion. These results resolve and define the structural heterogeneity of the S3 state, providing constraints on the S3 to S4 transition, on substrate identity and delivery pathways, and on the mechanism of O−O bond formation.

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“…Moreover, preliminary experiments done in plant PSII under conditions in which the S 2 HS form exhibits the g ∼ 4.1 signal suggest that this S 2 HS state is unable to progress to the S 3 S =3 state at 198 K and that, even at pH ∼ 8 (unpublished). Interestingly, a g ∼ 4.8-4.9 EPR signal with a resolved hyperfine structure was recently detected in plant PSII after the removal of the extrinsic proteins [85] and it would be interesting to know if this state is able to progress to S 3 at low temperatures.…”

Section: Discussionmentioning

confidence: 99%

“…Interestingly, a g ∼ 4.8 EPR signal with a resolved hyperfine structure was recently detected in plant PSII after the removal of the extrinsic proteins [92] and it would be interesting to know if this state is able to progress to S3 at low temperatures.…”

Section: Discussionmentioning

confidence: 99%

Probing the proton release by Photosystem II in the S₁ to S₂ high-spin transition

Boussac

Sugiura

Sellés

2022

Preprint

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The stoichiometry and kinetics of the proton release were investigated during each transition of the S-state cycle in Photosystem II (PSII) from Thermosynechococcus elongatus containing either a Mn4CaO5 (PSII/Ca) or a Mn4SrO5 (PSII/Sr) cluster. The measurements were done at pH 6.0 and pH 7.0 knowing that, in PSII/Ca at pH 6.0 and pH 7.0 and in PSII/Sr at pH 6.0, the flash-induced S2-state is in a low-spin configuration (S2LS) whereas in PSII/Sr at pH 7.0, the S2-state is in a high-spin configuration (S2HS) in half of the centers. Two measurements were done; the time-resolved flash dependent i) absorption of either bromocresol purple at pH 6.0 or neutral red at pH 7.0 and ii) electrochromism in the Soret band of PD1 at 440 nm. The fittings of the oscillations with a period of four indicate that one proton is released in the S1 to S2HS transition in PSII/Sr at pH 7.0. It was earlier suggested that the proton released in the S2LS to S3 transition is released in a S2LSTyrZ● to S2HSTyrZ● transition before the electron transfer from the cluster to TyrZ● occurs. The release of a proton in the S1TyrZ● to S2HSTyrZ transition would logically imply that this proton release is missing in the S2HSTyrZ● to S3TyrZ transition. Instead, the proton release in the S1 to S2HS transition in PSII/Sr at pH 7.0 was mainly done at the expense of the proton release in the S3 to S0 and S0 to S1 transitions. However, at pH 7.0, the electrochromism of PD1 seems larger in PSII/Sr when compared to PSII/Ca in the S3 state. This observation points to the complex link between proton movements in and immediately around the Mn4 cluster and the mechanism leading to the release of protons into the bulk.

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Molecular Structure of the S₂ State with a g = 5 Signal in the Oxygen Evolving Complex of Photosystem II

Cited by 20 publications

References 31 publications

Arrested Substrate Binding Resolves Catalytic Intermediates in Higher‐Plant Water Oxidation

Arrested Substrate Binding Resolves Catalytic Intermediates in Higher‐Plant Water Oxidation

Arrested Substrate Binding Resolves Catalytic Intermediates in Higher‐Plant Water Oxidation

Probing the proton release by Photosystem II in the S₁ to S₂ high-spin transition

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Molecular Structure of the S2 State with a g = 5 Signal in the Oxygen Evolving Complex of Photosystem II

Cited by 20 publications

References 31 publications

Arrested Substrate Binding Resolves Catalytic Intermediates in Higher‐Plant Water Oxidation

Arrested Substrate Binding Resolves Catalytic Intermediates in Higher‐Plant Water Oxidation

Arrested Substrate Binding Resolves Catalytic Intermediates in Higher‐Plant Water Oxidation

Probing the proton release by Photosystem II in the S1 to S2 high-spin transition

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Molecular Structure of the S₂ State with a g = 5 Signal in the Oxygen Evolving Complex of Photosystem II

Probing the proton release by Photosystem II in the S₁ to S₂ high-spin transition