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  The First State in the Catalytic Cycle of the Water-Oxidizing Enzyme: Identification of a Water-Derived μ-Hydroxo Bridge

Lohmiller, T., Krewald, V., Sedoud, A., Rutherford, A. W., Neese, F., Lubitz, W., et al. (2017). The First State in the Catalytic Cycle of the Water-Oxidizing Enzyme: Identification of a Water-Derived μ-Hydroxo Bridge. Journal of the American Chemical Society, 139(41), 14412-14424. doi:10.1021/jacs.7b05263.

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 Creators:
Lohmiller, Thomas1, Author              
Krewald, Vera1, Author
Sedoud, Arezki2, 3, Author
Rutherford, A. William2, 3, Author
Neese, Frank4, Author              
Lubitz, Wolfgang1, Author              
Pantazis, Dimitrios A.4, Author              
Cox, Nicholas1, 5, Author              
Affiliations:
1Research Department Lubitz, Max Planck Institute for Chemical Energy Conversion, Max Planck Society, ou_3023873              
2Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom, ou_persistent22              
3iBiTec-S, URA CNRS 2096, CEA Saclay, 91191 Gif-sur-Yvette, France, ou_persistent22              
4Research Department Neese, Max Planck Institute for Chemical Energy Conversion, Max Planck Society, ou_3023886              
5Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 2601, Australia, ou_persistent22              

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 Abstract: Nature’s water-splitting catalyst, an oxygen-bridged tetramanganese calcium (Mn4O5Ca) complex, sequentially activates two substrate water molecules generating molecular O2. Its reaction cycle is composed of five intermediate (Si) states, where the index i indicates the number of oxidizing equivalents stored by the cofactor. After formation of the S4 state, the product dioxygen is released and the cofactor returns to its lowest oxidation state, S0. Membrane-inlet mass spectrometry measurements suggest that at least one substrate is bound throughout the catalytic cycle, as the rate of 18O-labeled water incorporation into the product O2 is slow, on a millisecond to second time scale depending on the S state. Here, we demonstrate that the Mn4O5Ca complex poised in the S0 state contains an exchangeable hydroxo bridge. On the basis of a combination of magnetic multiresonance (EPR) spectroscopies, comparison to biochemical models and theoretical calculations we assign this bridge to O5, the same bridge identified in the S2 state as an exchangeable fully deprotonated oxo bridge [Pérez Navarro, M.; et al. Proc. Natl. Acad. Sci. U.S.A.2013, 110, 15561]. This oxygen species is the most probable candidate for the slowly exchanging substrate water in the S0 state. Additional measurements provide new information on the Mn ions that constitute the catalyst. A structural model for the S0 state is proposed that is consistent with available experimental data and explains the observed evolution of water exchange kinetics in the first three states of the catalytic cycle.

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Language(s): eng - English
 Dates: 2017-05-222017-10-032017-10-18
 Publication Status: Published in print
 Pages: 13
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/jacs.7b05263
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Title: Journal of the American Chemical Society
  Other : JACS
  Abbreviation : J. Am. Chem. Soc.
Source Genre: Journal
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Publ. Info: Washington, DC : American Chemical Society
Pages: - Volume / Issue: 139 (41) Sequence Number: - Start / End Page: 14412 - 14424 Identifier: ISSN: 0002-7863
CoNE: https://pure.mpg.de/cone/journals/resource/954925376870