title: X-ray spectroscopic observation of an interstitial carbide in NifEN-bound FeMoco precursor.
abstract: The iron-molybdenum cofactor (FeMoco) of nitrogenase contains a biologically unprecedented μ(6)-coordinated C(4-) ion. Although the role of this interstitial atom in nitrogenase catalysis is unknown, progress in understanding its biosynthetic origins has been made. Here we report valence-to-core Fe Kβ X-ray emission spectroscopy data to show that this C(4-) ion is present in the Fe(8)S(9) "L-cluster," which is the immediate precursor to FeMoco prior to the insertion of molybdenum and coordination by homocitrate. These results accord with recent evidence supporting a role for the S-adenosylmethionine-dependent enzyme NifB in the incorporation of carbon into the FeMoco center of nitrogenase.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Kyle M
authors.initials: KM
authors.lastname: Lancaster
authors.forename: Yilin
authors.initials: Y
authors.lastname: Hu
authors.forename: Uwe
authors.initials: U
authors.lastname: Bergmann
authors.forename: Markus W
authors.initials: MW
authors.lastname: Ribbe
authors.forename: Serena
authors.initials: S
authors.lastname: DeBeer
mesh_terms: D058085:Iron Compounds / Q000737:chemistry* / Q000378:metabolism; D015394:Molecular Structure; D008983:Molybdoferredoxin / Q000737:chemistry* / Q000378:metabolism; D013052:Spectrometry, X-Ray Emission; D014233:Tricarboxylic Acids / Q000737:chemistry
chemical_list: D058085:Iron Compounds; D008983:Molybdoferredoxin; C085381:NifB cofactor; D014233:Tricarboxylic Acids; C028143:homocitric acid