Oxidative Damage in MauG: Implications for the Control of High-Valent Iron Species and Radical Propagation Pathways

    Authors

    E. T. Yukl; H. R. Williamson; L. Higgins; V. L. Davidson;C. M. Wilmot

    Comments

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    Abbreviated Journal Title

    Biochemistry

    Keywords

    TRYPTOPHAN TRYPTOPHYLQUINONE; METHYLAMINE DEHYDROGENASE; HYDROGEN-PEROXIDE; BIOSYNTHESIS; BIOGENESIS; COMPLEX; HEME; Biochemistry & Molecular Biology

    Abstract

    The di-heme enzyme MauG catalyzes the oxidative biosynthesis of a tryptophan tryptophylquinone cofactor on a precursor of the enzyme methylamine dehydrogenase (preMADH). Reaction of H2O2 with the diferric form of MauG, or reaction of O-2 with diferrous MauG, forms the catalytic intermediate known as bis-Fe(IV), which acts as the key oxidant during turnover. The site of substrate oxidation is more than 40 angstrom from the high-spin heme iron where H2O2 initially reacts, and catalysis relies on radical hopping through an interfacial residue, Trp199 of MauG. In the absence of preMADH, the bis-Fe(IV) intermediate is remarkably stable, but repeated exposure to H2O2 results in suicide inactivation. Using mass spectrometry, we show that this process involves the oxidation of three Met residues (108, 114, and 116) near the high-spin heme through ancillary electron transfer pathways engaged in the absence of substrate. The mutation of a conserved Pro 107 in the distal pocket of the high-spin heme results in a dramatic increase in the level of oxidation of these Met residues. These results illustrate structural mechanisms by which MauG controls reaction with its high-valent heme cofactor and limits uncontrolled oxidation of protein residues and loss of catalytic activity. The conservation of Met residues near the high-spin heme among MauG homologues from different organisms suggests that eventual deactivation of MauG may function in a biological context. That is, methionine oxidation may represent a, protective mechanism that prevents the generation of reactive oxygen species by MauG in the absence of preMADH.

    Journal Title

    Biochemistry

    Volume

    52

    Issue/Number

    52

    Publication Date

    1-1-2013

    Document Type

    Article

    Language

    English

    First Page

    9447

    Last Page

    9455

    WOS Identifier

    WOS:000329331900005

    ISSN

    0006-2960

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