title: Biogenic Manganese-Oxide Mineralization is Enhanced by an Oxidative Priming Mechanism for the Multi-Copper Oxidase, MnxEFG.
abstract: In a natural geochemical cycle, manganese-oxide minerals (MnOx) are principally formed through a microbial process, where a putative multicopper oxidase MnxG plays an essential role. Recent success in isolating the approximately 230 kDa, enzymatically active MnxEFG protein complex, has advanced our understanding of biogenic MnOxmineralization. Here, the kinetics of MnOxformation catalyzed by MnxEFG are examined using a quartz crystal microbalance (QCM), and the first electrochemical characterization of the MnxEFG complex is reported using Fourier transformed alternating current voltammetry. The voltammetric studies undertaken using near-neutral solutions (pH 7.8) establish the apparent reversible potentials for the Type 2 Cu sites in MnxEFG immobilized on a carboxy-terminated monolayer to be in the range 0.36-0.40 V versus a normal hydrogen electrode. Oxidative priming of the MnxEFG protein complex substantially enhances the enzymatic activity, as found by in situ electrochemical QCM analysis. The biogeochemical significance of this enzyme is clear, although the role of an oxidative priming of catalytic activity might be either an evolutionary advantage or an ancient relic of primordial existence.
authors.affiliation: Department of Chemistry and Department of Earth and Planetary Sciences, University of California, One Shields Avenue, Davis, California, 95616, USA.
authors.forename: Lizhi
authors.initials: L
authors.lastname: Tao
authors.affiliation: School of Chemistry, Monash University, Victoria, 3800, Australia.|ARC Centre of Excellence for Electromaterials Science, Monash University, Victoria, 3800, Australia.
authors.forename: Alexandr N
authors.initials: AN
authors.lastname: Simonov
authors.affiliation: Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University, Portland, Oregon, 97239, USA.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Romano
authors.affiliation: Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University, Portland, Oregon, 97239, USA.|Current address: Department of Earth and Planetary Science, University of California Berkeley, Berkeley, California, 94720, USA.
authors.forename: Cristina N
authors.initials: CN
authors.lastname: Butterfield
authors.affiliation: School of Chemistry, Monash University, Victoria, 3800, Australia.
authors.forename: Monika
authors.initials: M
authors.lastname: Fekete
authors.affiliation: Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University, Portland, Oregon, 97239, USA.
authors.forename: Bradley M
authors.initials: BM
authors.lastname: Tebo
authors.affiliation: School of Chemistry, Monash University, Victoria, 3800, Australia.
authors.forename: Alan M
authors.initials: AM
authors.lastname: Bond
authors.affiliation: School of Chemistry, Monash University, Victoria, 3800, Australia.|ARC Centre of Excellence for Electromaterials Science, Monash University, Victoria, 3800, Australia.
authors.forename: Leone
authors.initials: L
authors.lastname: Spiccia
authors.affiliation: School of Chemistry, Monash University, Victoria, 3800, Australia.
authors.forename: Lisandra L
authors.initials: LL
authors.lastname: Martin
authors.affiliation: Department of Chemistry and Department of Earth and Planetary Sciences, University of California, One Shields Avenue, Davis, California, 95616, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Casey
mesh_terms: D055162:Biocatalysis; D055664:Electrochemical Techniques; D007700:Kinetics; D017895:Manganese Compounds / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D010087:Oxides / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D058525:Quartz Crystal Microbalance Techniques; D013052:Spectrometry, X-Ray Emission
chemical_list: D017895:Manganese Compounds; D010087:Oxides; C027424:manganese oxide; D010088:Oxidoreductases; C024748:copper oxidase
keywords: Fourier transformed AC voltammetry; direct protein electrochemistry; manganese oxide mineralization; multi-copper oxidase activity; quartz crystal microbalance