Document Type


Degree Name



Oregon Health & Science University


On Earth, the Mn geochemical cycle is becoming increasingly recognized as playing a significant role in the cycling of other elements. Especially reactive are the oxidized Mn species (Mn(III, IV)) in MnO 2 minerals which are abundant in the environment. Bacteria are believed to be the main driver in Mn oxidation catalysis so the mechanism of this process is of great scientific interest. The premier Mn oxidizing microbes in the laboratory have been the marine Bacillus species that mineralize Mn on the outside layer of their spores, the exosporium. In this thesis, the expression, purification, and characterization of the active Mn(II, III) oxidase from Bacillus sp. PL-12 is described. Several biochemical and bioinorganic methods, both straightforward and sophisticated, are employed to investigate the basic structural, metal binding, and catalytic features of the oxidase. The purified protein is a complex, named "Mnx", composed of the multicopper oxidase, MnxG, and MnxE and MnxF, previously "hypothetical proteins" but herein suggested as a novel Cu binding oligomer also capable of binding Fe heme. As a complex, Mnx is able to catalyze the most efficient enzymatic Mn oxidation described in addition to the oxidation of common MCO substrates, Fe and phenolic compounds. This work facilitates the investigation into the mechanism of Mn mineralization in the environment on the molecular level and the elucidation of unusual bioinorganic chemistry.




Environmental & Biomolecular Systems


School of Medicine



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