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Mn(II,III) oxidation and MnO2 mineralization by an expressed bacterial multicopper oxidase.
Butterfield, Cristina N; Soldatova, Alexandra V; Lee, Sung-Woo; Spiro, Thomas G; Tebo, Bradley M.
Afiliación
  • Butterfield CN; Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health and Science University, Beaverton, OR 97006, USA.
Proc Natl Acad Sci U S A ; 110(29): 11731-5, 2013 Jul 16.
Article en En | MEDLINE | ID: mdl-23818588
Reactive Mn(IV) oxide minerals are ubiquitous in the environment and control the bioavailability and distribution of many toxic and essential elements and organic compounds. Their formation is thought to be dependent on microbial enzymes, because spontaneous Mn(II) to Mn(IV) oxidation is slow. Several species of marine Bacillus spores oxidize Mn(II) on their exosporium, the outermost layer of the spore, encrusting them with Mn(IV) oxides. Molecular studies have identified the mnx (Mn oxidation) genes, including mnxG, encoding a putative multicopper oxidase (MCO), as responsible for this two-electron oxidation, a surprising finding because MCOs only catalyze single-electron transfer reactions. Characterization of the enzymatic mechanism has been hindered by the lack of purified protein. By purifying active protein from the mnxDEFG expression construct, we found that the resulting enzyme is a blue (absorption maximum 590 nm) complex containing MnxE, MnxF, and MnxG proteins. Further, by analyzing the Mn(II)- and (III)-oxidizing activity in the presence of a Mn(III) chelator, pyrophosphate, we found that the complex facilitates both electron transfers from Mn(II) to Mn(III) and from Mn(III) to Mn(IV). X-ray absorption spectroscopy of the Mn mineral product confirmed its similarity to Mn(IV) oxides generated by whole spores. Our results demonstrate that Mn oxidation from soluble Mn(II) to Mn(IV) oxides is a two-step reaction catalyzed by an MCO-containing complex. With the purification of active Mn oxidase, we will be able to uncover its mechanism, broadening our understanding of Mn mineral formation and the bioinorganic capabilities of MCOs.
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Texto completo: 1 Bases de datos: MEDLINE Asunto principal: Óxidos / Oxidorreductasas / Bacillus / Compuestos de Manganeso / Complejos Multiproteicos / Manganeso Tipo de estudio: Prognostic_studies Idioma: En Revista: Proc Natl Acad Sci U S A Año: 2013 Tipo del documento: Article País de afiliación: Estados Unidos

Texto completo: 1 Bases de datos: MEDLINE Asunto principal: Óxidos / Oxidorreductasas / Bacillus / Compuestos de Manganeso / Complejos Multiproteicos / Manganeso Tipo de estudio: Prognostic_studies Idioma: En Revista: Proc Natl Acad Sci U S A Año: 2013 Tipo del documento: Article País de afiliación: Estados Unidos