Crystal Structures of CO and NO Adducts of MauG in Complex with Pre-Methylamine Dehydrogenase: Implications for the Mechanism of Dioxygen Activation
- UMMC
MauG is a diheme enzyme responsible for the post-translational formation of the catalytic tryptophan tryptophylquinone (TTQ) cofactor in methylamine dehydrogenase (MADH). MauG can utilize hydrogen peroxide, or molecular oxygen and reducing equivalents, to complete this reaction via a catalytic bis-Fe(IV) intermediate. Crystal structures of diferrous, Fe(II)-CO, and Fe(II)-NO forms of MauG in complex with its preMADH substrate have been determined and compared to one another as well as to the structure of the resting diferric MauG-preMADH complex. CO and NO each bind exclusively to the 5-coordinate high-spin heme with no change in ligation of the 6-coordinate low-spin heme. These structures reveal likely roles for amino acid residues in the distal pocket of the high-spin heme in oxygen binding and activation. Glu113 is implicated in the protonation of heme-bound diatomic oxygen intermediates in promoting cleavage of the O-O bond. Pro107 is shown to change conformation on the binding of each ligand and may play a steric role in oxygen activation by positioning the distal oxygen near Glu113. Gln103 is in a position to provide a hydrogen bond to the Fe(IV){double_bond}O moiety that may account for the unusual stability of this species in MauG.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- OTHER U.S. STATESNCI
- OSTI ID:
- 1023649
- Journal Information:
- Biochemistry-US, Vol. 50, Issue (14) ; 04, 2011; ISSN 0006-2960
- Country of Publication:
- United States
- Language:
- ENGLISH
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