Abbreviated Journal Title
Proc. Natl. Acad. Sci. U. S. A.
Keywords
charge transfer; electron hopping; high-valent iron; metalloprotein; tryptophan radical; PI-CATION RADICALS; ELECTRON-TRANSFER; TRYPTOPHYLQUINONE BIOSYNTHESIS; OXIDATION-REDUCTION; OXYGEN ACTIVATION; REACTION CENTERS; INTERMEDIATE; DIMERS; HEME; DIMERIZATION; Multidisciplinary Sciences
Abstract
The diheme enzyme MauG catalyzes posttranslational modifications of a methylamine dehydrogenase precursor protein to generate a tryptophan tryptophylquinone cofactor. The MauG-catalyzed reaction proceeds via a bis-Fe(IV) intermediate in which one heme is present as Fe(IV)=O and the other as Fe(IV) with axial histidine and tyrosine ligation. Herein, a unique near-infrared absorption feature exhibited specifically in bis-Fe(IV) MauG is described, and evidence is presented that it results from a charge-resonance-transition phenomenon. As the two hemes are physically separated by 14.5 angstrom, a hole-hopping mechanism is proposed in which a tryptophan residue located between the hemes is reversibly oxidized and reduced to increase the effective electronic coupling element and enhance the rate of reversible electron transfer between the hemes in bis-Fe(IV) MauG. Analysis of the MauG structure reveals that electron transfer via this mechanism is rapid enough to enable a charge-resonance stabilization of the bis-Fe(IV) state without direct contact between the hemes. The finding of the charge-resonance-transition phenomenon explains why the bis-Fe(IV) intermediate is stabilized in MauG and does not permanently oxidize its own aromatic residues.
Journal Title
Proceedings of the National Academy of Sciences of the United States of America
Volume
110
Issue/Number
24
Publication Date
1-1-2013
Document Type
Article
Language
English
First Page
9639
Last Page
9644
WOS Identifier
ISSN
0027-8424
Recommended Citation
Geng, Jiafeng; Dornevil, Kednerlin; Davidson, Victor L.; and Liu, Aimin, "Tryptophan-mediated charge-resonance stabilization in the bis-Fe(IV) redox state of MauG" (2013). Faculty Bibliography 2010s. 4010.
https://stars.library.ucf.edu/facultybib2010/4010
Comments
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