EPR/ENDOR Studies of the Water Oxidizing Complex in Photosystem II

Fiege, Robert; Zweygart, W.; Irrgang, Klaus−Dieter; Adir, Noam; Geiken, B.; Ренгер, Г.; Lubitz, Wolfgang

doi:10.1007/978-94-009-0173-5_317

Cited by 10 publications

(16 citation statements)

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“…This "one-water, |F| ∼ 2" interpretation of the stronger deuteron interactions is also consistent with 1 H ENDOR studies on water binding to Mn in solvated ions and dinuclear complexes (17)(18)(19)(20)22). Assuming F ) 2, the A 1 and A 2 values from Table 2 correspond to single-ion proton A iso terms of 0.9-1.0 MHz.…”

Section: Mamedov Et Al Unpublished Observations) the Redox Active Tyr...supporting

confidence: 82%

“…ESEEM is most sensitive to n i and T di , with the A i term having a more subtle effect on the modulation damping. Several D 2 O exchangeable proton ENDOR studies on the S 2 state have been reported (17)(18)(19)(20)22). With powder pattern samples, the only quantity normally determined is the A ⊥ turning point value (in magnitude) of the total anisotropic hyperfine coupling.…”

Section: Mamedov Et Al Unpublished Observations) the Redox Active Tyr...mentioning

confidence: 99%

“…The difficulty in using 1 H or 2 H hyperfine sensitive spectroscopies is distinguishing those proton/deuteron couplings due to interaction of water with the paramagnetic center from interactions of hydrogen or an exchangeable deuteron with other nearby groups, particularly in a protein matrix. Nonetheless, techniques such as 2 H-1 H ESEEM or 1 H ENDOR are so experimentally convenient and sensitive that a number of studies have employed these methods to assess interactions of a proton (17)(18)(19)(20), exchangeable deuteron (21,22), and small molecule (23)(24)(25)(26)(27) with the Mn cluster in PSII.…”

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confidence: 99%

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ESEEM Studies of Substrate Water and Small Alcohol Binding to the Oxygen-Evolving Complex of Photosystem II during Functional Turnover

et al. 2006

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We report the first examination of exchangeable proton and MeOH interactions with the Mn catalytic cluster in photosystem II, under functional flash turnover conditions, using 2H ESEEM spectroscopy on the S2 and S0 multiline states. Deuterium-labeled water (D2O) and methyl d3-labeled methanol (DMeOH) are employed. It was discovered that a hyperfine resolved multiline S0 signal could be seen in the presence of D2O, the hyperfine structure of which depended on the presence or absence of methanol (MeOH). In the presence of DMeOH, significant dipolar coupling of the three methyl deuterons to the multiline centers in the S2 and S0 states was seen (S2, 0.65, 0.39(2) MHz; and S0, 0.60, 0.37(2) MHz). These are consistent with direct binding of the methoxy fragment to Mn. Assuming terminal Mn-OMe ligation, the couplings indicated a spin projection coefficient (rho) magnitude of approximately 2 for the ligating Mn in both the S2 and S0 states, with inferred Mn-O distances of approximately 1.9-2.0 A. In the presence of D2O, four classes of exchangeable deuterons were identified by ESEEM in S2 and S0. Three of these classes (1, 2, and 4) exhibited populations and coupling strengths that were essentially constant under various conditions of sample preparation, illumination turnover, and small alcohol addition. Class 3 could be modeled with constant coupling but a highly variable deuteron population (n3 approximately 0-10) depending in part on the preparation used. For all classes, the coupling parameters were very similar in S2 and S0. The favored interpretation is that the two strongest coupling classes (1 and 2) represent close binding of one water molecule to a single Mn which has an oxidation state of II in S0 and III in S2, and rho approximately 2 in both cases. This water is not displaced by MeOH, but either the water or MeOH is singly deprotonated upon MeOH binding. Class 4 represents approximately 2 water molecules which are not closely bound to Mn (Mn-deuteron distances of approximately 3.7-4.7 A). Class 3 probably represents protein matrix protons within approximately 4 A of the Mn in the cluster, which can be variably exchanged in different preparations.

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Section: Mamedov Et Al Unpublished Observations) the Redox Active Tyr...supporting

confidence: 82%

Section: Mamedov Et Al Unpublished Observations) the Redox Active Tyr...mentioning

confidence: 99%

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confidence: 99%

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ESEEM Studies of Substrate Water and Small Alcohol Binding to the Oxygen-Evolving Complex of Photosystem II during Functional Turnover

et al. 2006

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“…However, we tentatively assign these short-distance exchangeable hydrogens to water(s) or hydroxide(s) bound at the Mn cluster of the OEC. The strong hyperfine interactions that give rise to these assignments were not observed in previous continuous wave ENDOR experiments (Kawamori et al 1989;Tang et al 1993;Fiege et al 1996), probably because of the large breadth of the resultant ENDOR powder patterns. These data and their simulations together support a model of a 'wet' environment for the S 2 -state Mn cluster, with substrate water derived ligands already bound by S 2 .…”

Section: Discussionmentioning

confidence: 65%

Simulations of the ¹ H electron spin echo–electron nuclear double resonance and ² H electron spin echo envelope modulation spectra of exchangeable hydrogen nuclei coupled to the S ₂ –state photosystem II manganese cluster

Aznar

Britt

2002

Phil. Trans. R. Soc. Lond. B

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The pulsed EPR methods of electron spin echo envelope modulation (ESEEM) and electron spin echoelectron nuclear double resonance (ESE-ENDOR) are used to investigate the proximity of exchangeable hydrogens around the paramagnetic S 2 -state Mn cluster of the photosystem II oxygen-evolving complex. Although ESEEM and ESE-ENDOR are both pulsed electron paramagnetic resonance techniques, the specific mechanisms by which nuclear spin transitions are observed are quite different. We are able to generate good simulations of both 1 H ESE-ENDOR and 2 H ESEEM signatures of exchangeable hydrogens at the S 2 -state cluster. The convergence of simulation parameters for both methods provides a high degree of confidence in the simulations. Several exchangeable protons-deuterons with strong dipolar couplings are observed. In the simulations, two of the close (Ϸ2.5 Å ) hydrogen nuclei exhibit strong isotropic couplings and are therefore most probably associated with direct substrate ligation to paramagnetic Mn. Another two of the close (Ϸ2.7 Å ) hydrogen nuclei show no isotropic couplings and are therefore most probably not contained in Mn ligands. We suggest that these proximal hydrogens may be associated with a Ca 2ϩ -bound substrate, as indicated in recent mechanistic proposals for O 2 formation.

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“…In particular, the broad MLS (multiline signal) of the S 2 -state has been studied in different frequency bands and from different organisms [9,10]. ENDOR (electron nuclear double resonance) spectroscopy and ESEEM (electron spin-echo envelope modulation) spectroscopy on protons and nitrogen have been used for studying protein ligands and substrate binding to the WOC [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

55Mn-ENDOR of the S2-state multiline signal of Photosystem II from Thermosynechococcus elongatus

Pudollek

Lendzian

Bittl

2008

Biochemical Society Transactions

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Pulse EPR and 55Mn-ENDOR (electron nuclear double resonance) experiments at 34 GHz (Q-band) were performed on the S2 state of the OEC (oxygen-evolving complex) in PSII (Photosystem II) from Thermosynechococcus elongatus. The ENDOR spectra are discussed with respect to earlier data obtained from X- (9 GHz) and Q-band experiments on PSII preparations from spinach with and without the addition of methanol.

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EPR/ENDOR Studies of the Water Oxidizing Complex in Photosystem II

Cited by 10 publications

References 8 publications

ESEEM Studies of Substrate Water and Small Alcohol Binding to the Oxygen-Evolving Complex of Photosystem II during Functional Turnover

ESEEM Studies of Substrate Water and Small Alcohol Binding to the Oxygen-Evolving Complex of Photosystem II during Functional Turnover

Simulations of the ¹ H electron spin echo–electron nuclear double resonance and ² H electron spin echo envelope modulation spectra of exchangeable hydrogen nuclei coupled to the S ₂ –state photosystem II manganese cluster

55Mn-ENDOR of the S2-state multiline signal of Photosystem II from Thermosynechococcus elongatus

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EPR/ENDOR Studies of the Water Oxidizing Complex in Photosystem II

Cited by 10 publications

References 8 publications

ESEEM Studies of Substrate Water and Small Alcohol Binding to the Oxygen-Evolving Complex of Photosystem II during Functional Turnover

ESEEM Studies of Substrate Water and Small Alcohol Binding to the Oxygen-Evolving Complex of Photosystem II during Functional Turnover

Simulations of the 1 H electron spin echo–electron nuclear double resonance and 2 H electron spin echo envelope modulation spectra of exchangeable hydrogen nuclei coupled to the S 2 –state photosystem II manganese cluster

55Mn-ENDOR of the S2-state multiline signal of Photosystem II from Thermosynechococcus elongatus

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Simulations of the ¹ H electron spin echo–electron nuclear double resonance and ² H electron spin echo envelope modulation spectra of exchangeable hydrogen nuclei coupled to the S ₂ –state photosystem II manganese cluster