4L3H: Crystal Structure of the E113q-maug/pre-methylamine Dehydrogenase Complex After Treatment With Hydrogen Peroxide

Citation:
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 Glu113 in the formation of the bis-Fe(IV) state of MauG, in which one heme is Fe(IV) horizontal lineO 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.
PDB ID: 4L3HDownload
MMDB ID: 113257
PDB Deposition Date: 2013/6/5
Updated in MMDB: 2013/10
Experimental Method:
x-ray diffraction
Resolution: 1.79  Å
Source Organism:
Similar Structures:
Biological Unit for 4L3H: hexameric; determined by author and by software (PISA)
Molecular Components in 4L3H
Label Count Molecule
Proteins (6 molecules)
2
Methylamine Utilization Protein Maug
Molecule annotation
2
Methylamine Dehydrogenase Light Chain
Molecule annotation
2
Methylamine Dehydrogenase Heavy Chain
Molecule annotation
Chemicals (17 molecules)
1
2
2
4
3
4
4
4
5
2
6
1
* Click molecule labels to explore molecular sequence information.

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