title: Mn(II) Binding and Subsequent Oxidation by the Multicopper Oxidase MnxG Investigated by Electron Paramagnetic Resonance Spectroscopy.
abstract: The dynamics of manganese solid formation (as MnOx) by the multicopper oxidase (MCO)-containing Mnx protein complex were examined by electron paramagnetic resonance (EPR) spectroscopy. Continuous-wave (CW) EPR spectra of samples of Mnx, prepared in atmosphere and then reacted with Mn(II) for times ranging from 7 to 600 s, indicate rapid oxidation of the substrate manganese (with two-phase pseudo-first-order kinetics modeled using rate coefficients of: k(1obs) = 0.205 ± 0.001 s(-1) and k(2obs) = 0.019 ± 0.001 s(-1)). This process occurs on approximately the same time scale as in vitro solid MnOx formation when there is a large excess of Mn(II). We also found CW and pulse EPR spectroscopic evidence for at least three classes of Mn(II)-containing species in the reaction mixtures: (i) aqueous Mn(II), (ii) a specifically bound mononuclear Mn(II) ion coordinated to the Mnx complex by one nitrogenous ligand, and (iii) a weakly exchange-coupled dimeric Mn(II) species. These findings provide new insights into the molecular mechanism of manganese mineralization.
authors.forename: Lizhi
authors.initials: L
authors.lastname: Tao
authors.forename: Troy A
authors.initials: TA
authors.lastname: Stich
authors.affiliation: Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University , Portland, Oregon 97239, United States.
authors.forename: Cristina N
authors.initials: CN
authors.lastname: Butterfield
authors.affiliation: Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University , Portland, Oregon 97239, United States.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Romano
authors.affiliation: Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195, United States.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Spiro
authors.affiliation: Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University , Portland, Oregon 97239, United States.
authors.forename: Bradley M
authors.initials: BM
authors.lastname: Tebo
authors.forename: William H
authors.initials: WH
authors.lastname: Casey
authors.forename: R David
authors.initials: RD
authors.lastname: Britt
mesh_terms: D000818:Animals; D001407:Bacillus / Q000201:enzymology; D002417:Cattle; D019281:Dimerization; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D008345:Manganese / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry / Q000378:metabolism; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D010087:Oxides; D008345:Manganese; D010088:Oxidoreductases; C024748:copper oxidase