title: Two CO molecules can bind concomitantly at the diiron site of NO reductase from Bacillus azotoformans.
abstract: CO complexes formed in reduced nitric oxide reductase from Bacillus azotoformans were investigated with resonance Raman and FTIR techniques. These experiments shows the presence of two nu(C-O) bands, one at approximately 1970 cm-1 assigned to the heme-CO complex, and one at approximately 2070 cm-1 from the non-heme iron, FeBCO. At cryogenic temperatures, the heme-CO complex adopts a semi-bridging configuration with FeB which decreases its stretching frequency to approximately 1910 cm-1 and decreases the nu(C-O) of FeBCO by approximately 20 cm-1. The concomitant binding of two CO molecules, one per iron(II) at the active site, is consistent with the formation of a [{FeNO}7]2 iron-nitrosyl dimer during substrate turnover. This study strongly supports the notion that this family of enzymes utilizes a reaction mechanism based on catalysis by proximity, where the formation of two iron-nitrosyl groups promotes N-N bond formation.
authors.affiliation: Department of Environmental & Biomolecular Systems, OGI School of Science & Engineering, Oregon Health & Science University, Beaverton, OR 97006-8921, USA.
authors.forename: Shen
authors.initials: S
authors.lastname: Lu
authors.lastname: Suharti
authors.forename: Simon
authors.initials: S
authors.lastname: de Vries
authors.forename: Pierre
authors.initials: P
authors.lastname: Moënne-Loccoz
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002248:Carbon Monoxide / Q000737:chemistry / Q000378:metabolism*; D002712:Chlorides / Q000737:chemistry; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D019159:Nonheme Iron Proteins / Q000737:chemistry / Q000378:metabolism*; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D001426:Bacterial Proteins; D002712:Chlorides; D019159:Nonheme Iron Proteins; D006418:Heme; D002248:Carbon Monoxide; D010088:Oxidoreductases; C034747:nitric-oxide reductase