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Site-specific oxidation state assignments of the irons in the [4Fe:4S]^(2+/1+/0) states of the nitrogenase Fe-protein

Wenke, Belinda B. and Spatzal, Thomas and Rees, Douglas C. (2019) Site-specific oxidation state assignments of the irons in the [4Fe:4S]^(2+/1+/0) states of the nitrogenase Fe-protein. Angewandte Chemie International Edition, 58 (12). pp. 3894-3897. ISSN 1433-7851.

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The nitrogenase iron protein (Fe‐protein) contains an unusual [4Fe:4S] iron‐sulphur cluster that is stable in three oxidation states: 2+, 1+, and 0. Here, we use spatially resolved anomalous dispersion (SpReAD) refinement to determine oxidation assignments for the individual irons for each state. Additionally, we report the 1.13‐Å resolution structure for the ADP bound Fe‐protein, the highest resolution Fe‐protein structure presently determined. In the dithionite‐reduced [4Fe:4S]^(1+) state, our analysis identifies a solvent exposed, delocalized Fe2.5+ pair and a buried Fe^(2+) pair. We propose that ATP binding by the Fe‐protein promotes an internal redox rearrangement such that the solvent‐exposed Fe pair becomes reduced, thereby facilitating electron transfer to the nitrogenase molybdenum iron‐protein. In the [4Fe:4S]^0 and [4Fe:4S]^(2+) states, the SpReAD analysis supports oxidation states assignments for all irons in these clusters of Fe^(2+) and valence delocalized Fe^(2.5+), respectively.

Item Type:Article
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URLURL TypeDescription
Wenke, Belinda B.0000-0003-3214-6197
Spatzal, Thomas0000-0002-9136-5915
Rees, Douglas C.0000-0003-4073-1185
Additional Information:© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Accepted manuscript online: 30 January 2019; Manuscript accepted: 18 January 2019; Manuscript received: 14 December 2018. We thank Prof. O. Einsle, Prof. L. Zhang, Dr. K. Perez, Dr. R. Arias, A. Maggiolo, and Prof. J. B. Howard for informative discussions, and K. H. Lee for the initial identification of the ADP‐bound Fe‐protein crystals. We acknowledge the Gordon and Betty Moore Foundation and the Beckman Institute at Caltech for their generous support of the Molecular Observatory at Caltech. We thank the staff at Beamline 12‐2, Stanford Synchrotron Radiation Lightsource (SSRL), operated for the DOE and supported by its OBER and by the NIH, NIGMS (P41GM103393), and the NCRR (P41RR001209). We also thank Dr. A. Di Bilio for assisting with EPR experiments. The Caltech EPR Facility was supported by NSF‐1531940. This work was supported by NIH grant GM045162 and the Howard Hughes Medical Institute. The authors declare no conflict of interest.
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
Subject Keywords:nitrogenase; iron sulphur cluster; metalloprotein crystallography; multiwavelength anomalous diffraction
Record Number:CaltechAUTHORS:20190201-083038828
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Official Citation:B. B. Wenke, T. Spatzal, D. C. Rees, Angew. Chem. Int. Ed. 2019, 58, 3894; doi: 10.1002/anie.201813966
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92551
Deposited By: Tony Diaz
Deposited On:01 Feb 2019 17:20
Last Modified:25 Mar 2019 11:20

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