title: X-ray emission spectroscopy evidences a central carbon in the nitrogenase iron-molybdenum cofactor.
abstract: Nitrogenase is a complex enzyme that catalyzes the reduction of dinitrogen to ammonia. Despite insight from structural and biochemical studies, its structure and mechanism await full characterization. An iron-molybdenum cofactor (FeMoco) is thought to be the site of dinitrogen reduction, but the identity of a central atom in this cofactor remains unknown. Fe Kβ x-ray emission spectroscopy (XES) of intact nitrogenase MoFe protein, isolated FeMoco, and the FeMoco-deficient nifB protein indicates that among the candidate atoms oxygen, nitrogen, and carbon, it is carbon that best fits the XES data. The experimental XES is supported by computational efforts, which show that oxidation and spin states do not affect the assignment of the central atom to C(4-). Identification of the central atom will drive further studies on its role in catalysis.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Kyle M
authors.initials: KM
authors.lastname: Lancaster
authors.forename: Michael
authors.initials: M
authors.lastname: Roemelt
authors.forename: Patrick
authors.initials: P
authors.lastname: Ettenhuber
authors.forename: Yilin
authors.initials: Y
authors.lastname: Hu
authors.forename: Markus W
authors.initials: MW
authors.lastname: Ribbe
authors.forename: Frank
authors.initials: F
authors.lastname: Neese
authors.forename: Uwe
authors.initials: U
authors.lastname: Bergmann
authors.forename: Serena
authors.initials: S
authors.lastname: DeBeer
mesh_terms: D016948:Azotobacter vinelandii / Q000737:chemistry; D055162:Biocatalysis; D002244:Carbon / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D008983:Molybdoferredoxin / Q000737:chemistry* / Q000378:metabolism; D009584:Nitrogen / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission
chemical_list: D008024:Ligands; D008983:Molybdoferredoxin; D002244:Carbon; D009584:Nitrogen; D010100:Oxygen
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