Title

Carboxyl Group of Glu113 Is Required for Stabilization of the Diferrous and Bis-Fe-IV States of MauG

Authors

Authors

N. Abu Tarboush; E. T. Yukl; S. Shin; M. L. Feng; C. M. Wilmot;V. L. Davidson

Comments

Authors: contact us about adding a copy of your work at STARS@ucf.edu

Abbreviated Journal Title

Biochemistry

Keywords

TRYPTOPHAN TRYPTOPHYLQUINONE BIOSYNTHESIS; CYTOCHROME-C PEROXIDASE; DI-HEME PEROXIDASES; METHYLAMINE DEHYDROGENASE; CRYSTAL-STRUCTURE; STRUCTURAL BASIS; DIFFERENT FORMS; SPIN HEME; PROTEIN; MECHANISM; Biochemistry & Molecular Biology

Abstract

The diheme enzyme MauG catalyzes a six-electron oxidation required for post-translational modification of a precursor of methylamine dehydrogenase (preMADH) to complete the biosynthesis of its protein-derived tryptophan tryptophylquinone (TTQ) cofactor. Crystallographic studies have implicated Glul 13 in the formation of the bis-Fe-IV state of MauG, in which one heme is Fe-IV=O and the other is Few with His-Tyr axial ligation. An E113Q mutation had no effect on the structure of MauG but significantly altered its redox properties. E113Q MauG could not be converted to the diferrous state by reduction with dithionite but was only reduced to a mixed valence Fe-II/Fe-III state, which is never observed in wild-type (WT) MauG. Addition of H2O2 to E113Q MauG generated a high valence state that formed more slowly and was less stable than the bis-Fe-IV state of WT MauG. E113Q MauG exhibited no detectable TTQ biosynthesis activity in a steady-state assay with preMADH as the substrate. It did catalyze the steady-state oxidation of quinol MADH to the quinone, but 1000-fold less efficiently than WT MauG. Addition of H2O2 to a crystal of the E113Q MauG-preMADH complex resulted in partial synthesis of TTQ Extended exposure of these crystals to H2O2 resulted in hydroxylation of Pro 107 in the distal pocket of the high-spin heme. It is concluded that the loss of the carboxylic group of Glu113 disrupts the redox cooperativity between hemes that allows rapid formation of the diferrous state and alters the distribution of high-valence species that participate in charge-resonance stabilization of the bis-Fe-IV redox state.

Journal Title

Biochemistry

Volume

52

Issue/Number

37

Publication Date

1-1-2013

Document Type

Article

Language

English

First Page

6358

Last Page

6367

WOS Identifier

WOS:000330099600007

ISSN

0006-2960

Share

COinS