title: Ultrafast ligand binding dynamics in the active site of native bacterial nitric oxide reductase.
abstract: The active site of nitric oxide reductase from Paracoccus denitrificans contains heme and non-heme iron and is evolutionarily related to heme-copper oxidases. The CO and NO dynamics in the active site were investigated using ultrafast transient absorption spectroscopy. We find that, upon photodissociation from the active site heme, 20% of the CO rebinds in 170 ps, suggesting that not all the CO transiently binds to the non-heme iron. The remaining 80% does not rebind within 4 ns and likely migrates out of the active site without transient binding to the non-heme iron. Rebinding of NO to ferrous heme takes place in approximately 13 ps. Our results reveal that heme-ligand recombination in this enzyme is considerably faster than in heme-copper oxidases and are consistent with a more confined configuration of the active site.
authors.affiliation: Laboratoire d'Optique et Biosciences, CNRS, Ecole Polytechnique, F-91128 Palaiseau, France; INSERM U696, F-91128 Palaiseau, France.
authors.forename: Sofia M
authors.initials: SM
authors.lastname: Kapetanaki
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Field
authors.forename: Ross J L
authors.initials: RJ
authors.lastname: Hughes
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Watmough
authors.forename: Ursula
authors.initials: U
authors.lastname: Liebl
authors.forename: Marten H
authors.initials: MH
authors.lastname: Vos
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D002248:Carbon Monoxide / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D008024:Ligands; D009569:Nitric Oxide / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D010231:Paracoccus denitrificans / Q000201:enzymology*; D011485:Protein Binding; D013053:Spectrophotometry
chemical_list: D001426:Bacterial Proteins; D008024:Ligands; D009569:Nitric Oxide; D002248:Carbon Monoxide; D010088:Oxidoreductases; C034747:nitric-oxide reductase