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PDBsum entry 4l3h
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Oxidoreductase
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PDB id
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4l3h
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Contents |
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354 a.a.
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129 a.a.
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376 a.a.
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References listed in PDB file
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Key reference
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Title
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Carboxyl group of glu113 is required for stabilization of the diferrous and bis-Fe(IV) states of maug.
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Authors
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N.Abu tarboush,
E.T.Yukl,
S.Shin,
M.Feng,
C.M.Wilmot,
V.L.Davidson.
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Ref.
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Biochemistry, 2013,
52,
6358-6367.
[DOI no: ]
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PubMed id
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Abstract
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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
Glu113 in the formation of the bis-Fe(IV) state of MauG, in which one heme is
Fe(IV)═O and the other is Fe(IV) 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 Pro107 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.
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