The Basic Properties of the Electronic Structure of the Oxygen-evolving Complex of Photosystem II Are Not Perturbed by Ca2+ Removal*. Lohmiller, T., Cox, N., Su, J., Messinger, J., & Lubitz, W. Journal of Biological Chemistry, 287(29):24721–24733, July, 2012. ![The Basic Properties of the Electronic Structure of the Oxygen-evolving Complex of Photosystem II Are Not Perturbed by Ca2+ Removal* [link]](https://bibbase.org/img/filetypes/link.svg "link")
Paper doi abstract bibtex Ca2+ is an integral component of the Mn4O5Ca cluster of the oxygen-evolving complex in photosystem II (PS II). Its removal leads to the loss of the water oxidizing functionality. The S2′ state of the Ca2+-depleted cluster from spinach is examined by X- and Q-band EPR and 55Mn electron nuclear double resonance (ENDOR) spectroscopy. Spectral simulations demonstrate that upon Ca2+ removal, its electronic structure remains essentially unaltered, i.e. that of a manganese tetramer. No redistribution of the manganese valence states and only minor perturbation of the exchange interactions between the manganese ions were found. Interestingly, the S2′ state in spinach PS II is very similar to the native S2 state of Thermosynechococcus elongatus in terms of spin state energies and insensitivity to methanol addition. These results assign the Ca2+ a functional as opposed to a structural role in water splitting catalysis, such as (i) being essential for efficient proton-coupled electron transfer between YZ and the manganese cluster and/or (ii) providing an initial binding site for substrate water. Additionally, a novel 55Mn2+ signal, detected by Q-band pulse EPR and ENDOR, was observed in Ca2+-depleted PS II. Mn2+ titration, monitored by 55Mn ENDOR, revealed a specific Mn2+ binding site with a submicromolar KD. Ca2+ titration of Mn2+-loaded, Ca2+-depleted PS II demonstrated that the site is reversibly made accessible to Mn2+ by Ca2+ depletion and reconstitution. Mn2+ is proposed to bind at one of the extrinsic subunits. This process is possibly relevant for the formation of the Mn4O5Ca cluster during photoassembly and/or D1 repair. Background: EPR/55Mn ENDOR spectroscopy of the oxygen-evolving complex (OEC) and Mn2+ in Ca2+-depleted photosystem II. Results: Electronic model of the Ca2+-depleted OEC; characterization of Mn2+ binding. Conclusion: Ca2+ is not critical for maintaining the electronic and spatial structure of the OEC. Its removal exposes a Mn2+ binding site supposedly in an extrinsic subunit. Significance: Mechanistic implications for water oxidation; Mn2+ in photoassembly/D1 protein repair.
@article{lohmiller_basic_2012,
title = {The {Basic} {Properties} of the {Electronic} {Structure} of the {Oxygen}-evolving {Complex} of {Photosystem} {II} {Are} {Not} {Perturbed} by {Ca2}+ {Removal}*},
volume = {287},
issn = {0021-9258},
url = {https://www.sciencedirect.com/science/article/pii/S002192582043323X},
doi = {10.1074/jbc.M112.365288},
abstract = {Ca2+ is an integral component of the Mn4O5Ca cluster of the oxygen-evolving complex in photosystem II (PS II). Its removal leads to the loss of the water oxidizing functionality. The S2′ state of the Ca2+-depleted cluster from spinach is examined by X- and Q-band EPR and 55Mn electron nuclear double resonance (ENDOR) spectroscopy. Spectral simulations demonstrate that upon Ca2+ removal, its electronic structure remains essentially unaltered, i.e. that of a manganese tetramer. No redistribution of the manganese valence states and only minor perturbation of the exchange interactions between the manganese ions were found. Interestingly, the S2′ state in spinach PS II is very similar to the native S2 state of Thermosynechococcus elongatus in terms of spin state energies and insensitivity to methanol addition. These results assign the Ca2+ a functional as opposed to a structural role in water splitting catalysis, such as (i) being essential for efficient proton-coupled electron transfer between YZ and the manganese cluster and/or (ii) providing an initial binding site for substrate water. Additionally, a novel 55Mn2+ signal, detected by Q-band pulse EPR and ENDOR, was observed in Ca2+-depleted PS II. Mn2+ titration, monitored by 55Mn ENDOR, revealed a specific Mn2+ binding site with a submicromolar KD. Ca2+ titration of Mn2+-loaded, Ca2+-depleted PS II demonstrated that the site is reversibly made accessible to Mn2+ by Ca2+ depletion and reconstitution. Mn2+ is proposed to bind at one of the extrinsic subunits. This process is possibly relevant for the formation of the Mn4O5Ca cluster during photoassembly and/or D1 repair. Background: EPR/55Mn ENDOR spectroscopy of the oxygen-evolving complex (OEC) and Mn2+ in Ca2+-depleted photosystem II. Results: Electronic model of the Ca2+-depleted OEC; characterization of Mn2+ binding. Conclusion: Ca2+ is not critical for maintaining the electronic and spatial structure of the OEC. Its removal exposes a Mn2+ binding site supposedly in an extrinsic subunit. Significance: Mechanistic implications for water oxidation; Mn2+ in photoassembly/D1 protein repair.},
number = {29},
urldate = {2024-12-10},
journal = {Journal of Biological Chemistry},
author = {Lohmiller, Thomas and Cox, Nicholas and Su, Ji-Hu and Messinger, Johannes and Lubitz, Wolfgang},
month = jul,
year = {2012},
keywords = {Calcium, ENDOR Spectroscopy, Electron Paramagnetic Resonance (EPR), Manganese, Metalloproteins, Oxygen-evolving Complex (OEC), Photoassembly/Photoactivation, Photosystem II, Water-oxidizing Complex (WOC), Zero-field Splitting},
pages = {24721--24733},
}
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Spectral simulations demonstrate that upon Ca2+ removal, its electronic structure remains essentially unaltered, i.e. that of a manganese tetramer. No redistribution of the manganese valence states and only minor perturbation of the exchange interactions between the manganese ions were found. Interestingly, the S2′ state in spinach PS II is very similar to the native S2 state of Thermosynechococcus elongatus in terms of spin state energies and insensitivity to methanol addition. These results assign the Ca2+ a functional as opposed to a structural role in water splitting catalysis, such as (i) being essential for efficient proton-coupled electron transfer between YZ and the manganese cluster and/or (ii) providing an initial binding site for substrate water. Additionally, a novel 55Mn2+ signal, detected by Q-band pulse EPR and ENDOR, was observed in Ca2+-depleted PS II. Mn2+ titration, monitored by 55Mn ENDOR, revealed a specific Mn2+ binding site with a submicromolar KD. Ca2+ titration of Mn2+-loaded, Ca2+-depleted PS II demonstrated that the site is reversibly made accessible to Mn2+ by Ca2+ depletion and reconstitution. Mn2+ is proposed to bind at one of the extrinsic subunits. This process is possibly relevant for the formation of the Mn4O5Ca cluster during photoassembly and/or D1 repair. Background: EPR/55Mn ENDOR spectroscopy of the oxygen-evolving complex (OEC) and Mn2+ in Ca2+-depleted photosystem II. Results: Electronic model of the Ca2+-depleted OEC; characterization of Mn2+ binding. Conclusion: Ca2+ is not critical for maintaining the electronic and spatial structure of the OEC. Its removal exposes a Mn2+ binding site supposedly in an extrinsic subunit. Significance: Mechanistic implications for water oxidation; Mn2+ in photoassembly/D1 protein repair.","number":"29","urldate":"2024-12-10","journal":"Journal of Biological Chemistry","author":[{"propositions":[],"lastnames":["Lohmiller"],"firstnames":["Thomas"],"suffixes":[]},{"propositions":[],"lastnames":["Cox"],"firstnames":["Nicholas"],"suffixes":[]},{"propositions":[],"lastnames":["Su"],"firstnames":["Ji-Hu"],"suffixes":[]},{"propositions":[],"lastnames":["Messinger"],"firstnames":["Johannes"],"suffixes":[]},{"propositions":[],"lastnames":["Lubitz"],"firstnames":["Wolfgang"],"suffixes":[]}],"month":"July","year":"2012","keywords":"Calcium, ENDOR Spectroscopy, Electron Paramagnetic Resonance (EPR), Manganese, Metalloproteins, Oxygen-evolving Complex (OEC), Photoassembly/Photoactivation, Photosystem II, Water-oxidizing Complex (WOC), Zero-field Splitting","pages":"24721–24733","bibtex":"@article{lohmiller_basic_2012,\n\ttitle = {The {Basic} {Properties} of the {Electronic} {Structure} of the {Oxygen}-evolving {Complex} of {Photosystem} {II} {Are} {Not} {Perturbed} by {Ca2}+ {Removal}*},\n\tvolume = {287},\n\tissn = {0021-9258},\n\turl = {https://www.sciencedirect.com/science/article/pii/S002192582043323X},\n\tdoi = {10.1074/jbc.M112.365288},\n\tabstract = {Ca2+ is an integral component of the Mn4O5Ca cluster of the oxygen-evolving complex in photosystem II (PS II). Its removal leads to the loss of the water oxidizing functionality. The S2′ state of the Ca2+-depleted cluster from spinach is examined by X- and Q-band EPR and 55Mn electron nuclear double resonance (ENDOR) spectroscopy. Spectral simulations demonstrate that upon Ca2+ removal, its electronic structure remains essentially unaltered, i.e. that of a manganese tetramer. No redistribution of the manganese valence states and only minor perturbation of the exchange interactions between the manganese ions were found. Interestingly, the S2′ state in spinach PS II is very similar to the native S2 state of Thermosynechococcus elongatus in terms of spin state energies and insensitivity to methanol addition. These results assign the Ca2+ a functional as opposed to a structural role in water splitting catalysis, such as (i) being essential for efficient proton-coupled electron transfer between YZ and the manganese cluster and/or (ii) providing an initial binding site for substrate water. Additionally, a novel 55Mn2+ signal, detected by Q-band pulse EPR and ENDOR, was observed in Ca2+-depleted PS II. Mn2+ titration, monitored by 55Mn ENDOR, revealed a specific Mn2+ binding site with a submicromolar KD. Ca2+ titration of Mn2+-loaded, Ca2+-depleted PS II demonstrated that the site is reversibly made accessible to Mn2+ by Ca2+ depletion and reconstitution. Mn2+ is proposed to bind at one of the extrinsic subunits. This process is possibly relevant for the formation of the Mn4O5Ca cluster during photoassembly and/or D1 repair. Background: EPR/55Mn ENDOR spectroscopy of the oxygen-evolving complex (OEC) and Mn2+ in Ca2+-depleted photosystem II. Results: Electronic model of the Ca2+-depleted OEC; characterization of Mn2+ binding. Conclusion: Ca2+ is not critical for maintaining the electronic and spatial structure of the OEC. Its removal exposes a Mn2+ binding site supposedly in an extrinsic subunit. 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