Nitrogenase FeMoco investigated by spatially resolved anomalous dispersion refinement
Abstract
The [Mo:7Fe:9S:C] iron-molybdenum cofactor (FeMoco) of nitrogenase is the largest known metal cluster and catalyses the 6-electron reduction of dinitrogen to ammonium in biological nitrogen fixation. Only recently its atomic structure was clarified, while its reactivity and electronic structure remain under debate. Here we show that for its resting S=3/2 state the common iron oxidation state assignments must be reconsidered. By a spatially resolved refinement of the anomalous scattering contributions of the 7 Fe atoms of FeMoco, we conclude that three irons (Fe1/3/7) are more reduced than the other four (Fe2/4/5/6). Our data are in agreement with the recently revised oxidation state assignment for the molybdenum ion, providing the first spatially resolved picture of the resting-state electron distribution within FeMoco. This might provide the long-sought experimental basis for a generally accepted theoretical description of the cluster that is in line with available spectroscopic and functional data.
Additional Information
© 2016 Nature Publishing Group. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received 25 Aug 2015. Accepted 31 Jan 2016. Published 14 Mar 2016. We thank Serena DeBeer for stimulating and helpful discussions and the staff at the Swiss Light Source, Villigen, CH, and the Stanford Synchrotron Radiation Laboratory, Palo Alto, CA, USA, for assistance during data collection. We acknowledge the Gordon and Betty Moore Foundation and the Beckman Institute at Caltech for their generous support of the Molecular Observatory at Caltech. This work was supported by the Deutsche Forschungsgemeinschaft (RTG 1976 to S.L.A. and O.E. and EI 520/7 to O.E.) and the European Research Council (grant 310656 to O.E.), NIH (grant GM45162 to D.C.R.) and an NSERC PDF award (L.M.Z.). Author contributions: T.S., S.L.A., D.C.R. and O.E. designed the experiments; T.S., J.S. and E.-M.B. performed the experiments; T.S., L.Z., D.S., S.L.A., D.C.R. and O.E. analysed the data; T.S., S.L.A. and O.E. wrote the paper. Competing financial interests: The authors declare no competing financial interests.Attached Files
Published - ncomms10902.pdf
Supplemental Material - ncomms10902-s1.pdf
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Additional details
- PMCID
- PMC4793075
- Eprint ID
- 65564
- Resolver ID
- CaltechAUTHORS:20160322-065458303
- Gordon and Betty Moore Foundation
- Caltech Beckman Institute
- Deutsche Forschungsgemeinschaft (DFG)
- RTG 1976
- Deutsche Forschungsgemeinschaft (DFG)
- EI 520/7
- European Research Council (ERC)
- 310656
- NIH
- GM45162
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- Created
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2016-03-22Created from EPrint's datestamp field
- Updated
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2022-05-05Created from EPrint's last_modified field