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Mn oxide mineral formation by an expressed bacterial Mn(II,III)-oxidizing multicopper oxidase


EMSL Project ID
47955

Abstract

Microbial Mn(II) oxidation is an important environmental process that links the biogeochemical cycle of Mn with the cycling of C, N, P, and many trace metals and radionuclides. The Mn oxides produced by microbes are some of the strongest oxidants found in the environment, participating in a wide range of redox reactions with organic and inorganic chemical species and compounds. There are several mechanisms, both direct and indirect, by which bacteria oxidize Mn(II). One mechanism identified in several environmentally important groups of bacteria mostly through genetic studies involves enzymatic catalysis by Mn(II)-oxidizing multicopper oxidases (MCOs). These Mn(II)-oxidizing MCOs are novel because they appear to catalyze a two-electron process, oxidation of Mn(II) to Mn(IV), whereas all other known MCOs catalyze only one-electron oxidation reactions. Over the years these Mn(II)-oxidizing MCOs have resisted study because they are large, are in relatively low abundance, appear to be part of a larger complex and in general are difficult to purify in an active form either biochemically via traditional chromatographic techniques or after cloning and expressing genes in another organism. We have recently had success in expressing in E. coli the active Mn oxidase from an environmental isolate, Bacillus sp. strain PL-12 by including the three genes upstream of the MCO along with the MCO gene on the expression plasmid. The active enzyme is a protein complex composed of the MCO and at least 2 accessory proteins, another unique feature of this MCO. We propose to use EMSL mass spectrometry and microscopy facilities to help elucidate the structure of the enzyme complex and the mechanism of Mn oxide biomineralization. Specifically we will examine the composition and stoichiometry of the different proteins in the complex, the role of the accessory proteins, the architecture of the Mn oxidase complex in vivo and the molecular details that lead to the formation of a layered-structure Mn(IV) oxide mineral. This protein may have potential biotechnological applications such as in contaminant remediation applications or bioenergy production.

Project Details

Project type
Large-Scale EMSL Research
Start Date
2013-10-01
End Date
2015-09-30
Status
Closed

Team

Principal Investigator

Bradley Tebo
Institution
University of Washington

Team Members

Christine Romano
Institution
Oregon Health & Science University

Alexandra Soldatova
Institution
University of Washington

Cristina Butterfield
Institution
Oregon Health & Science University

Thomas Spiro
Institution
University of Washington

Related Publications

Zhou M, J Yan, CA Romano, BM Tebo, VH Wysocki, and L Pasa Tolic. 2018. "Surface Induced Dissociation coupled with High Resolution Mass Spectrometry Unveils Heterogeneity from Variable Metal Binding and Unexpected Modifications in an Uncharacterized 211 kDa Multicopper Oxidase Protein Complex." Journal of the American Society for Mass Spectrometry. doi:10.1007/s13361-017-1882-x