Title
Tryptophan tryptophylquinone biosynthesis: A radical approach to posttranslational modification
Abbreviated Journal Title
BBA-Proteins Proteomics
Keywords
Cytochrome; Electron transfer; Ferryl intermediate; Heme; MauG; Methylamine dehydrogenase; ELECTRON-TRANSFER COMPLEX; CYTOCHROME-C PEROXIDASE; METHYLAMINE; DEHYDROGENASE; PARACOCCUS-DENITRIFICANS; CRYSTAL-STRUCTURE; MAUG; AMICYANIN; PROTEIN; COFACTOR; MUTAGENESIS; Biochemistry & Molecular Biology; Biophysics
Abstract
Protein-derived cofactors are formed by irreversible covalent posttranslational modification of amino acid residues. An example is tryptophan tryptophylquinone (TTQ) found in the enzyme methylamine dehydrogenase (MADH). TTQ biosynthesis requires the cross-linking of the indole rings of two Trp residues and the insertion of two oxygen atoms onto adjacent carbons of one of the indole rings. The diheme enzyme MauG catalyzes the completion of TTQ within a precursor protein of MADH. The preMADH substrate contains a single hydroxyl group on one of the tryptophans and no crosslink. MauG catalyzes a six-electron oxidation that completes TTQ assembly and generates fully active MADH. These oxidation reactions proceed via a high valent bis-Fe(IV) state in which one heme is present as Fe(IV)=O and the other is Fe(IV) with both axial heme ligands provided by amino acid side chains. The crystal structure of MauG in complex with preMADH revealed that catalysis does not involve direct contact between the hemes of MauG and the protein substrate. Rather it is accomplished through long-range electron transfer, which presumably generates radical intermediates. Kinetic, spectrophotometric, and site-directed mutagenesis studies are beginning to elucidate how the MauG protein controls the reactivity of the hemes and mediates the long range electron/radical transfer required for catalysis. This article is part of a Special Issue entitled: Radical SAM enzymes and Radical Enzymology. (C) 2012 Elsevier B.V. All rights reserved.
Journal Title
Biochimica Et Biophysica Acta-Proteins and Proteomics
Volume
1824
Issue/Number
11
Publication Date
1-1-2012
Document Type
Review
Language
English
First Page
1299
Last Page
1305
WOS Identifier
ISSN
1570-9639
Recommended Citation
"Tryptophan tryptophylquinone biosynthesis: A radical approach to posttranslational modification" (2012). Faculty Bibliography 2010s. 2464.
https://stars.library.ucf.edu/facultybib2010/2464
Comments
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