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Structural Characterization of Two CO Molecules Bound to the Nitrogenase Active Site

Buscagan, Trixia M. and Perez, Kathryn A. and Maggiolo, Ailiena O. and Rees, Douglas C. and Spatzal, Thomas (2021) Structural Characterization of Two CO Molecules Bound to the Nitrogenase Active Site. Angewandte Chemie International Edition, 60 (11). pp. 5704-5707. ISSN 1433-7851. PMCID PMC7920927.

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As an approach towards unraveling the nitrogenase mechanism, we have studied the binding of CO to the active‐site FeMo‐cofactor. CO is not only an inhibitor of nitrogenase, but it is also a substrate, undergoing reduction to hydrocarbons (Fischer–Tropsch‐type chemistry). The C−C bond forming capabilities of nitrogenase suggest that multiple CO or CO‐derived ligands bind to the active site. Herein, we report a crystal structure with two CO ligands coordinated to the FeMo‐cofactor of the molybdenum nitrogenase at 1.33 Å resolution. In addition to the previously observed bridging CO ligand between Fe2 and Fe6 of the FeMo‐cofactor, a new ligand binding mode is revealed through a second CO ligand coordinated terminally to Fe6. While the relevance of this state to nitrogenase‐catalyzed reactions remains to be established, it highlights the privileged roles for Fe2 and Fe6 in ligand binding, with multiple coordination modes available depending on the ligand and reaction conditions.

Item Type:Article
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URLURL TypeDescription - ACIE CentralArticle
Buscagan, Trixia M.0000-0001-8242-9203
Perez, Kathryn A.0000-0003-1707-5060
Maggiolo, Ailiena O.0000-0003-1707-5060
Rees, Douglas C.0000-0003-4073-1185
Spatzal, Thomas0000-0002-9136-5915
Additional Information:© 2020 The Authors. Angewandte Chemie published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Issue Online: 01 March 2021; Version of Record online: 27 January 2021; Accepted manuscript online: 15 December 2020; Manuscript received: 25 November 2020. We thank the Gordon and Betty Moore Foundation and the Beckman Institute at Caltech for their generous support of the Molecular Observatory at Caltech. We thank Prof. James B. Howard, Dr. Rebeccah Warmack, Dr. Renee Arias, Dr. Belinda Wenke, Dr. Stephanie Threatt, and Siobhán MacArdle for insightful discussions, Dr. Jens Kaiser for support of crystallographic data collection, Jeffrey Lai for growing Azotobacter vinelandii, and Dr. Paul Oyala for EPR training and support. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, 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). This research was supported by the National Institute of Health (NIH Grant GM45162) and the Howard Hughes Medical Institute. The Caltech EPR Facility is supported by NSF‐1531940. The authors declare no conflict of interest.
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Department of Energy (DOE)DE-AC02-76SF00515
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
Subject Keywords:carbonyl ligands; C−C coupling; cofactors; nitrogenases; X-ray diffraction
Issue or Number:11
PubMed Central ID:PMC7920927
Record Number:CaltechAUTHORS:20201218-102813715
Persistent URL:
Official Citation:Structural Characterization of Two CO Molecules Bound to the Nitrogenase Active Site. T. M. Buscagan, K. A. Perez, A. O. Maggiolo, D. C. Rees, T. Spatzal, Angew. Chem. Int. Ed. 2021, 60, 5704; DOI: 10.1002/ange.202015751
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107199
Deposited By: Tony Diaz
Deposited On:18 Dec 2020 18:50
Last Modified:26 Aug 2021 19:06

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