title: Spectroscopic properties of the hydroxylase of methane monooxygenase.
abstract: The hydroxylase component of methane monooxygenase (EC 1.14.13.25), which catalyzes the oxidation of methane to methanol, has been studied by visible, electron spin resonance and X-ray spectroscopies. The enzyme appears to possess a mu-oxo- or mu-hydroxo-bridged binuclear iron site, with no sulfur ligands to the cluster. Each Fe has 4-6 oxygen (or nitrogen) ligands, at an average distance of 1.92 +/- 0.03 A. The Fe-Fe distance is 3.05 +/- 0.05 A. Essentially all of the irons are in the Fe3+ state as the enzyme is prepared, but reduction with N-methylphenazonium methosulfate generates ESR-detectable states that appear to emanate from mixed-valence binuclear sites. One of these, with gav near 1.85, displays typical Curie law microwave saturation behavior, but the other, gav near 1.73, has a very potent method of spin-relaxation. Together they account for approximately 0.6 spins per molecule.
authors.affiliation: Exxon Research and Engineering Co., Annandale, NJ 08801.
authors.forename: R C
authors.initials: RC
authors.lastname: Prince
authors.forename: G N
authors.initials: GN
authors.lastname: George
authors.forename: J C
authors.initials: JC
authors.lastname: Savas
authors.forename: S P
authors.initials: SP
authors.lastname: Cramer
authors.forename: R N
authors.initials: RN
authors.lastname: Patel
mesh_terms: D001665:Binding Sites; D004578:Electron Spin Resonance Spectroscopy; D019605:Euryarchaeota / Q000201:enzymology*; D007501:Iron / Q000032:analysis; D007700:Kinetics; D006899:Mixed Function Oxygenases; D010105:Oxygenases / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D013053:Spectrophotometry; D013057:Spectrum Analysis; D013816:Thermodynamics
chemical_list: D007501:Iron; D006899:Mixed Function Oxygenases; D010105:Oxygenases; C021555:methane monooxygenase