. The goal of this proposal is to understand how dioxygen is activated by biological diiron centers in metabolically critical transformations. Nonheme diiron proteins and enzymes perform a variety of essential functions involving dioxygen, including dioxygen transport (hemerythrin), DMA biosynthesis (ribonucleotide reductase), iron storage (ferritin), and oxidations of organic substrates (methane monooxygenase, fatty acid desaturases, alkane and arene hydroxylases, myo-inositol oxygenase, deoxyhypusine hydroxylase). In general, dioxygen activation is proposed to entail a common mechanism involving diiron(lll)-peroxo intermediates and high-valent iron-oxo species derived therefrom. The project goal will be accomplished using a combination of biomimetic and spectroscopic approaches. Building on past accomplishments in modeling structural and spectroscopic properties of such sites, it is proposed to synthesize precursor complexes of tripodal ligands, to react them with O2 or peroxides, and to characterize the metastable intermediates derived therefrom. Of great interest are intermediates such as O2 adducts of diiron(ll) complexes (either iron(ll)iron(lll)-superoxo or diiron(lll)-peroxo species), and species with Fe(lll-)Fe(-IV) and Fe(-IV)Fe(-lV) oxidation states. These complexes will be characterized by X-ray crystallography whenever possible and by a variety of techniques such as NMR, EPR, UV-vis-NIR, Raman, Mossbauer, electrospray mass spectrometry, electrochemistry, and EXAFS. Both stopped-flow and conventional kinetic methods will be used to characterize their mechanisms of formation and decomposition. The oxidative reactivities of these transient complexes towards a range of substrates will be investigated and compared with those of enzyme active sites. Also to be synthesized are complexes that can serve as precedents for the novel oxygen activation mechanism recently proposed for myo-inositol oxygenase entailing an iron(ll)iron(lll) center that binds O2 and a diiron(lll)-superoxo species that acts as the initial oxidant. Parallel to these efforts, our spectroscopic expertise will be applied to elucidating the diiron site structures of methane monooxygenase intermediates and deoxyhypusine hydroxylase. Relevance. Nonheme diiron enzymes perform a variety of metabolically critical functions that require dioxygen activation. Understanding how these enzymes work can lead to the development of new drug strategies for treating some human diseases. For example, myo-inositol oxygenase may be connected to the many complications associated with diabetes mellitus, while deoxyhypusine hydroxylase is required for the formation of mature eukaryotic elongation factor 5a that is essential for cell proliferation and may thus serve as the target for anti-tumor or anti-HIV therapy.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM038767-23
Application #
7791435
Study Section
Macromolecular Structure and Function A Study Section (MSFA)
Program Officer
Anderson, Vernon
Project Start
1999-04-01
Project End
2011-03-31
Budget Start
2010-04-01
Budget End
2011-03-31
Support Year
23
Fiscal Year
2010
Total Cost
$282,960
Indirect Cost
Name
University of Minnesota Twin Cities
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
555917996
City
Minneapolis
State
MN
Country
United States
Zip Code
55455
Castillo, Rebeca G; Banerjee, Rahul; Allpress, Caleb J et al. (2017) High-Energy-Resolution Fluorescence-Detected X-ray Absorption of the Q Intermediate of Soluble Methane Monooxygenase. J Am Chem Soc 139:18024-18033
Komor, Anna J; Rivard, Brent S; Fan, Ruixi et al. (2017) CmlI N-Oxygenase Catalyzes the Final Three Steps in Chloramphenicol Biosynthesis without Dissociation of Intermediates. Biochemistry 56:4940-4950
Jasniewski, Andrew J; Komor, Anna J; Lipscomb, John D et al. (2017) Unprecedented (?-1,1-Peroxo)diferric Structure for the Ambiphilic Orange Peroxo Intermediate of the Nonheme N-Oxygenase CmlI. J Am Chem Soc 139:10472-10485
Khenkin, Alexander M; Vedichi, Madhu; Shimon, Linda J W et al. (2017) Hydrogen-Atom Transfer Oxidation with H2O2 Catalyzed by [FeII(1,2-bis(2,2'-bipyridyl-6-yl)ethane(H2O)2]2+: Likely Involvement of a (?-Hydroxo)(?-1,2-peroxo)diiron(III) Intermediate. Isr J Chem 57:990-998
Zhou, Ang; Prakash, Jai; Rohde, Gregory T et al. (2017) The Two Faces of Tetramethylcyclam in Iron Chemistry: Distinct Fe-O-M Complexes Derived from [FeIV(Oanti/syn)(TMC)]2+ Isomers. Inorg Chem 56:518-527
Draksharapu, Apparao; Rasheed, Waqas; Klein, Johannes E M N et al. (2017) Facile and Reversible Formation of Iron(III)-Oxo-Cerium(IV) Adducts from Nonheme Oxoiron(IV) Complexes and Cerium(III). Angew Chem Int Ed Engl 56:9091-9095
Komor, Anna J; Rivard, Brent S; Fan, Ruixi et al. (2016) Mechanism for Six-Electron Aryl-N-Oxygenation by the Non-Heme Diiron Enzyme CmlI. J Am Chem Soc 138:7411-21
Jasniewski, Andrew J; Engstrom, Lisa M; Vu, Van V et al. (2016) X-ray absorption spectroscopic characterization of the diferric-peroxo intermediate of human deoxyhypusine hydroxylase in the presence of its substrate eIF5a. J Biol Inorg Chem 21:605-18
Jasniewski, Andrew J; Knoot, Cory J; Lipscomb, John D et al. (2016) A Carboxylate Shift Regulates Dioxygen Activation by the Diiron Nonheme ?-Hydroxylase CmlA upon Binding of a Substrate-Loaded Nonribosomal Peptide Synthetase. Biochemistry 55:5818-5831
Ye, Shengfa; Xue, Genqiang; Krivokapic, Itana et al. (2015) Magnetic circular dichroism and computational study of mononuclear and dinuclear iron(IV) complexes. Chem Sci 6:2909-2921

Showing the most recent 10 out of 57 publications