title: Determination by X-ray absorption spectroscopy of the Fe-Fe separation in the oxidized form of the hydroxylase of methane monooxygenase alone and in the presence of MMOD.
abstract: The diiron active site in the hydroxylase of Methylococcus capsulatus (Bath) methane monooxygenase (MMOH) has been studied in the oxidized form by X-ray absorption spectroscopy (XAS). Previous investigations by XAS and X-ray crystallography have identified two different distances (3.0 and 3.4 angstroms) between the two Fe atoms in the dinuclear site. The present study has employed a systematic extended X-ray absorption fine structure (EXAFS) fitting methodology, utilizing known and simulated active site and relevant model structures, to determine unambiguously the Fe-Fe separation in the oxidized form of MMOH. Consistent and unique fits were only possible for an Fe-Fe distance of 3.0 angstroms. This methodology was then applied to study potential changes in the active site local structure in the presence of MMOD, a protein of unknown function in multicomponent MMO. Fe K-edge and EXAFS analyses revealed negligible changes in the diiron site electronic and geometric structure upon addition of MMOD to oxidized MMOH.
authors.affiliation: Departments of Chemistry, Stanford University, Stanford, California 94305, USA.
authors.forename: Deanne Jackson
authors.initials: DJ
authors.lastname: Rudd
authors.forename: Matthew H
authors.initials: MH
authors.lastname: Sazinsky
authors.forename: Maarten
authors.initials: M
authors.lastname: Merkx
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lippard
authors.forename: Britt
authors.initials: B
authors.lastname: Hedman
authors.forename: Keith O
authors.initials: KO
authors.lastname: Hodgson
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism; D020619:Methylococcus capsulatus / Q000201:enzymology*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation
chemical_list: D005290:Ferric Compounds; D010105:Oxygenases; C021555:methane monooxygenase