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  Five-coordinate Mn-IV intermediate in the activation of nature's water splitting cofactor

Chrysina, M., Heyno, E., Kutin, Y., Reus, M., Nilsson, H., Nowaczyk, M. M., et al. (2019). Five-coordinate Mn-IV intermediate in the activation of nature's water splitting cofactor. Proceedings of the National Academy of Sciences of the United States of America, 116(34), 16841-16846. doi:10.1073/pnas.1817526116.

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 Creators:
Chrysina, Maria1, Author           
Heyno, Eiri, Author
Kutin, Yuri2, Author           
Reus, Michael1, Author           
Nilsson, Hakan, Author
Nowaczyk, Marc M., Author
DeBeer, Serena1, Author           
Neese, Frank3, Author           
Messinger, Johannes, Author
Lubitz, Wolfgang2, Author           
Cox, Nicholas, Author
Affiliations:
1Research Department DeBeer, Max Planck Institute for Chemical Energy Conversion, Max Planck Society, ou_3023871              
2Research Department Lubitz, Max Planck Institute for Chemical Energy Conversion, Max Planck Society, ou_3023873              
3Research Department Neese, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_2541710              

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 Abstract: Nature's water splitting cofactor passes through a series of catalytic intermediates (S-0-S-4) before O-O bond formation and O-2 release. In the second last transition (S-2 to S-3) cofactor oxidation is coupled to water molecule binding to Mn1. It is this activated, water-enriched all Mn-IV form of the cofactor that goes on to form the O-O bond, after the next light-induced oxidation to S-4. How cofactor activation proceeds remains an open question. Here, we report a so far not described intermediate (S-3') in which cofactor oxidation has occurred without water insertion. This intermediate can be trapped in a significant fraction of centers (> 50%) in (i) chemical-modified cofactors in which Ca2+ is exchanged with Sr2+; the Mn4O5Sr cofactor remains active, but the S-2-S-3 and S-3-S-0 transitions are slower than for the Mn4O5Ca cofactor; and (ii) upon addition of 3% vol/vol methanol; methanol is thought to act as a substrate water analog. The S-3' electron paramagnetic resonance (EPR) signal is significantly broader than the untreated S-3 signal (2.5 T vs. 1.5 T), indicating the cofactor still contains a 5-coordinate Mn ion, as seen in the preceding S-2 state. Magnetic double resonance data extend these findings revealing the electronic connectivity of the S-3' cofactor is similar to the high spin form of the preceding S-2 state, which contains a cuboidal Mn3O4Ca unit tethered to an external, 5-coordinate Mn ion (Mn-4). These results demonstrate that cofactor oxidation regulates water molecule insertion via binding to Mn-4. The interaction of ammonia with the cofactor is also discussed.

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Language(s): eng - English
 Dates: 2019
 Publication Status: Issued
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: ISI: 000481935500034
DOI: 10.1073/pnas.1817526116
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Title: Proceedings of the National Academy of Sciences of the United States of America
  Other : Proc. Acad. Sci. USA
  Other : Proc. Acad. Sci. U.S.A.
  Other : Proceedings of the National Academy of Sciences of the USA
  Abbreviation : PNAS
Source Genre: Journal
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Publ. Info: Washington, D.C. : National Academy of Sciences
Pages: - Volume / Issue: 116 (34) Sequence Number: - Start / End Page: 16841 - 16846 Identifier: ISSN: 0027-8424
CoNE: https://pure.mpg.de/cone/journals/resource/954925427230