title: Thiolate S-oxygenation controls nitric oxide (NO) photolability of a synthetic iron nitrile hydratase (Fe-NHase) model derived from mixed carboxamide/thiolate ligand.
abstract: In order to determine the origin of the NO photolability of the active site of Fe-containing nitrile hydratase (Fe-NHase), a model complex of the NO-bound active site (dark form) has been isolated and structurally characterized. The model, NEt(4)[(Cl(2)PhPepS)Fe(NO)(DMAP)] (2), is derived from a tetradentate ligand comprising carboxamido N and thiolato S donor centers much like the donors present in the active site of Fe-NHase. This {Fe-NO}(6) nitrosyl effectively mimics the NO-bound active site in terms of structural and spectroscopic parameters. However, this model lacks the key property of NO photolability. Interestingly, S-oxygenation of the model complex results in formation of Na[(Cl(2)PhPep{SO(2)}(2))Fe(NO)(DMAP)] (3), in which the -S donors are oxygenated to -SO(2) moieties, and this species exhibits NO photolability. These results indicate that S-oxygenation could be the key reason for the observed NO photolability of the active site of the dark form of Fe-NHase.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 96064, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rose
authors.forename: Nolan M
authors.initials: NM
authors.lastname: Betterley
authors.forename: Pradip K
authors.initials: PK
authors.lastname: Mascharak
mesh_terms: D000577:Amides / Q000737:chemistry*; D020134:Catalytic Domain; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D006836:Hydro-Lyases / Q000737:chemistry*; D008024:Ligands; D009569:Nitric Oxide / Q000737:chemistry*; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D011725:Pyridines / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: C417980:4-(dimethylamine)pyridine; D000577:Amides; D005290:Ferric Compounds; D008024:Ligands; D011725:Pyridines; D013438:Sulfhydryl Compounds; D009569:Nitric Oxide; D006836:Hydro-Lyases; C048831:nitrile hydratase