Heme and Protein Radical-Mediated Remote Enzyme Catalysis Project Description Understanding how an enzyme specifically oxidizes a protein substrate that is much larger than the enzyme itself will illuminate the mechanism by which proteins mature through enzyme-mediated posttranslational modifications. Given the interconnectedness of protein posttranslational modification, metabolic chemistry, and diseases, the question of how enzymes preserve specificity for large protein substrates is fundamental to enzymology. We are studying the long-range remote enzyme catalysis mechanism required for the biogenesis of a protein-derived tryptophan tryptophylquinone (TTQ) cofactor. TTQ is the catalytic center of methylamine dehydrogenase. This proposal seeks to determine the chemical properties of two reactive intermediates, an unprecedented bis-FeIV state of a di-heme enzyme MauG and a novel tryptophan-based di-radical in the substrate protein preMADH. Both are critical catalytic intermediates that occur sequentially in the catalytic cycle of TTQ biogenesis. Characterization of these key intermediates will lead to comprehension of the TTQ biogenesis mechanism, which in turn will provide insight into long-range enzyme-mediated remote oxidative and oxygenation chemical modification strategies. These studies will begin with examining the nature of the electronic interactions between the two hemes and the chemical reactivity, stability, and spectroscopic signature of the high-valent bis-FeIV state of MauG. Then, we will follow up with spectroscopic, structural, and theoretical characterizations of the tryptophan-based di-radical intermediate in the substrate protein to elucidate the coupling nature of the di-radical species and the proton release mechanism necessary for cross-linking and subsequent oxidation reactions.

Public Health Relevance

Free radicals and reactive oxygen species are double-edged swords. On one hand, they are the primary culprits for non-specific oxidative damage to cell components, leading to oxidative stress, aging, and mitochondrial disease states. On the other hand, many critical metabolic events depend on protein-based free radicals and reactive oxygen species that are produced and consumed in a controlled manner. The proposed research will elucidate how an iron-dependent enzyme generates protein-based radicals in a tightly controlled manner to produce cofactors necessary for sustaining life.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM108988-01A1
Application #
8761645
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Barski, Oleg
Project Start
2014-08-01
Project End
2018-03-31
Budget Start
2014-08-01
Budget End
2015-03-31
Support Year
1
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Georgia State University
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
City
Atlanta
State
GA
Country
United States
Zip Code
30302
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Shin, Inchul; Ambler, Brett R; Wherritt, Daniel et al. (2018) Stepwise O-Atom Transfer in Heme-Based Tryptophan Dioxygenase: Role of Substrate Ammonium in Epoxide Ring Opening. J Am Chem Soc 140:4372-4379
Davis, Ian; Yang, Yu; Wherritt, Daniel et al. (2018) Reassignment of the human aldehyde dehydrogenase ALDH8A1 (ALDH12) to the kynurenine pathway in tryptophan catabolism. J Biol Chem 293:9594-9603
Wang, Yifan; Griffith, Wendell P; Li, Jiasong et al. (2018) Cofactor Biogenesis in Cysteamine Dioxygenase: C-F Bond Cleavage with Genetically Incorporated Unnatural Tyrosine. Angew Chem Int Ed Engl 57:8149-8153
Yang, Yu; Liu, Fange; Liu, Aimin (2018) Adapting to oxygen: 3-Hydroxyanthrinilate 3,4-dioxygenase employs loop dynamics to accommodate two substrates with disparate polarities. J Biol Chem 293:10415-10424
Davis, Ian; Koto, Teruaki; Liu, Aimin (2018) Radical Trapping Study of the Relaxation of bis-Fe(IV) MauG. React Oxyg Species (Apex) 5:46-55
Davis, Ian; Koto, Teruaki; Terrell, James R et al. (2018) High-Frequency/High-Field Electron Paramagnetic Resonance and Theoretical Studies of Tryptophan-Based Radicals. J Phys Chem A 122:3170-3176
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Wang, Yifan; Li, Jiasong; Liu, Aimin (2017) Oxygen activation by mononuclear nonheme iron dioxygenases involved in the degradation of aromatics. J Biol Inorg Chem 22:395-405
Fielding, Andrew J; Dornevil, Kednerlin; Ma, Li et al. (2017) Probing Ligand Exchange in the P450 Enzyme CYP121 from Mycobacterium tuberculosis: Dynamic Equilibrium of the Distal Heme Ligand as a Function of pH and Temperature. J Am Chem Soc 139:17484-17499

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