Structural Effects of Ammonia Binding to the Mn_4CaO_5 Cluster of Photosystem II
Abstract
The Mn_4CaO_5 oxygen-evolving complex (OEC) of photosystem II catalyzes the light-driven oxidation of two substrate waters to molecular oxygen. ELDOR-detected NMR along with computational studies indicated that ammonia, a substrate analogue, binds as a terminal ligand to the Mn4A ion trans to the O5 μ_4 oxido bridge. Results from electron spin echo envelope modulation (ESEEM) spectroscopy confirmed this and showed that ammonia hydrogen bonds to the carboxylate side chain of D1-Asp61. Here we further probe the environment of OEC with an emphasis on the proximity of exchangeable protons, comparing ammonia-bound and unbound forms. Our ESEEM and electron nuclear double resonance (ENDOR) results indicate that ammonia substitutes for the W1 terminal water ligand without significantly altering the electronic structure of the OEC.
Additional Information
© 2018 American Chemical Society. Received: November 9, 2017; Revised: January 3, 2018; Published: January 5, 2018. This work was funded by the Division of Chemical Sciences, Geosciences, and Biosciences (R.D.B. grant DE-SC0007203 for EPR studies of the OEC; R.J.D. grant DESC0005291 for mutant construction and sample preparation) of the Office of Basic Energy Sciences of the U.S. Department of Energy. The authors declare no competing financial interest.Attached Files
Supplemental Material - jp7b11101_si_001.pdf
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Additional details
- Alternative title
- Structural Effects of Ammonia Binding to the Mn4CaO5 Cluster of Photosystem II
- Eprint ID
- 84554
- Resolver ID
- CaltechAUTHORS:20180129-084432031
- DE-SC0007203
- Department of Energy (DOE)
- DE-SC0005291
- Department of Energy (DOE)
- Created
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2018-01-30Created from EPrint's datestamp field
- Updated
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2021-11-15Created from EPrint's last_modified field