Oxygen Activation and Long-range Electron Transfer in MauG

Abstract

MauG is an enzyme responsible for the maturation of the tryptophan tryptophylquinone (TTQ) cofactor of methylamine dehydrogenase (MADH) from an inactive precursor protein (preMADH). The reaction involves a six-electron oxidation of the substrate and requires the formation of an unusual high-valent di-heme species, an Fev equivalent referred to as bis-Feiv. This species can be formed either by reaction of H2O2 with the diferric form or activation of O2 by the diferrous form of MauG. Stabilization of bis-Feiv and catalysis involves ultrafast electron transfer between MauG hemes and efficient hole hopping through a series of Trp residues connecting the enzyme and substrate. MauG thus provides an excellent system to study the mechanisms of long-range electron transfer and radical stabilization that are essential for critical biological processes.