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Localized Electronic Structure of Nitrogenase FeMoco Revealed by Selenium K-edge High Resolution X-ray Absorption Spectroscopy

Henthorn, Justin T. and Arias, Renee J. and Koroidov, Sergey and Kroll, Thomas and Sokaras, Dimosthenis and Bergmann, Uwe and Rees, Douglas C. and DeBeer, Serena (2019) Localized Electronic Structure of Nitrogenase FeMoco Revealed by Selenium K-edge High Resolution X-ray Absorption Spectroscopy. Journal of the American Chemical Society, 141 (34). pp. 13676-13688. ISSN 0002-7863. PMCID PMC6716209.

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The size and complexity of Mo-dependent nitrogenase, a multicomponent enzyme capable of reducing dinitrogen to ammonia, have made a detailed understanding of the FeMo cofactor (FeMoco) active site electronic structure an ongoing challenge. Selective substitution of sulfur by selenium in FeMoco affords a unique probe wherein local Fe–Se interactions can be directly interrogated via high-energy resolution fluorescence detected X-ray absorption spectroscopic (HERFD XAS) and extended X-ray absorption fine structure (EXAFS) studies. These studies reveal a significant asymmetry in the electronic distribution of the FeMoco, suggesting a more localized electronic structure picture than is typically assumed for iron–sulfur clusters. Supported by experimental small molecule model data in combination with time dependent density functional theory (TDDFT) calculations, the HERFD XAS data is consistent with an assignment of Fe2/Fe6 as an antiferromagnetically coupled diferric pair. HERFD XAS and EXAFS have also been applied to Se-substituted CO-inhibited MoFe protein, demonstrating the ability of these methods to reveal electronic and structural changes that occur upon substrate binding. These results emphasize the utility of Se HERFD XAS and EXAFS for selectively probing the local electronic and geometric structure of FeMoco.

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URLURL TypeDescription CentralArticle
Henthorn, Justin T.0000-0003-4876-2680
Arias, Renee J.0000-0002-6505-7513
Bergmann, Uwe0000-0001-5639-166X
Rees, Douglas C.0000-0003-4073-1185
DeBeer, Serena0000-0002-5196-3400
Additional Information:© 2019 American Chemical Society. This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. Received: July 2, 2019; Published: July 29, 2019. J.T.H. and S.D. thank the Max Planck Society for funding. S.D. acknowledges funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 615414 and the DFG SPP 1927 “Iron Sulfur for Life” project (Project No. DE 1877/1-1). J.T.H. acknowledges funding from the Alexander von Humboldt Foundation. S.K. would like to thank The Knut and Alice Wallenberg Foundation (KAW 2014.0370) for financial support. We are grateful to Dr. T. Weyhermüller and T. Mußfeldt for supplying [Et4N]2[Fe2Se2(SPh)4]. We thank the Gordon and Betty Moore Foundation and the Beckman Institute at Caltech for their generous support of the Molecular Observatory at Caltech, the staff of SSRL BL12-2 for their technical assistance. Support from NIH Grant GM045162 and the Howard Hughes Medical Institute to D.C.R. and from NIH Training Grant T32GM7616 to R.J.A. is gratefully acknowledged. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-76SF00515. The SSRL Structural Molecular Biology Program is supported by the DOE Office of Biological and Environmental Research and by the National Institutes of Health, National Institute of General Medical Sciences (including P41GM103393). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of NIGMS or NIH. We thank Paul Oyala and the Electron Paramagnetic Resonance Facility at Caltech for assistance with EPR measurements. Author Contributions: J.T.H. and R.J.A. contributed equally. The authors declare no competing financial interest. Crystallographic data has been uploaded to the PDB.
Funding AgencyGrant Number
Max Planck SocietyUNSPECIFIED
European Research Council (ERC)615414
Deutsche Forschungsgemeinschaft (DFG)SPP 1927
Deutsche Forschungsgemeinschaft (DFG)DE 1877/1-1
Alexander von Humboldt FoundationUNSPECIFIED
Knut and Alice Wallenberg FoundationKAW 2014.0370
Gordon and Betty Moore FoundationUNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
NIH Predoctoral FellowshipT32GM7616
Department of Energy (DOE)DE-AC02-76SF00515
Issue or Number:34
PubMed Central ID:PMC6716209
Record Number:CaltechAUTHORS:20190729-142108096
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Official Citation:Localized Electronic Structure of Nitrogenase FeMoco Revealed by Selenium K-Edge High Resolution X-ray Absorption Spectroscopy. Justin T. Henthorn, Renee J. Arias, Sergey Koroidov, Thomas Kroll, Dimosthenis Sokaras, Uwe Bergmann, Douglas C. Rees, and Serena DeBeer. Journal of the American Chemical Society 2019 141 (34), 13676-13688. DOI: 10.1021/jacs.9b06988
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97491
Deposited By: Tony Diaz
Deposited On:30 Jul 2019 16:05
Last Modified:03 Oct 2019 21:32

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