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Structural Characterization of Two CO Molecules Bound to the Nitrogenase Active Site
Author(s) -
Buscagan Trixia M.,
Perez Kathryn A.,
Maggiolo Ailiena O.,
Rees Douglas C.,
Spatzal Thomas
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202015751
Subject(s) - nitrogenase , chemistry , ligand (biochemistry) , cofactor , active site , stereochemistry , binding site , molecule , molybdenum , bridging ligand , crystal structure , crystallography , enzyme , biochemistry , inorganic chemistry , receptor , nitrogen fixation , organic chemistry , nitrogen
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.

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