The overall goal of this proposal is to understand how dioxygen is activated by biological diiron centers to carry out metabolically critical transformations. Nonheme diiron enzymes perform a variety of dioxygen-dependent essential functions, including the biosynthesis of DNA (ribonucleotide reductase), iron storage (ferritin), and the hydroxylation of organic substrates (methane monooxygenase, arene hydroxylases, deoxyhypusine hydroxylase). In general, dioxygen activation is proposed to entail a common mechanism involving diiron(III)- peroxo intermediates. Important project goals are to understand how the diiron(III)-peroxo intermediates are converted to corresponding high-valent iron-oxo species that very likely act as the key oxidants for substrate transformation and to describe the structural, electronic, and reactivity properties of the high-valent intermediates. These goals will be accomplished by both biochemical and biomimetic approaches. The biochemical effort will primarily focus on human deoxyhypusine hydroxylase, an enzyme that hydroxylates a deoxyhypusine residue on eukaryotic initiation factor 5A to generate a mature form that is required for eukaryotic cell proliferation and implicated in HIV-1 transcription initiation. This enzyme has a diiron active site and is isolated in an unusually stable diiron(III)-peroxo form that is nevertheless capable of substrate hydroxylation. The diiron active site will be investigated by a combination of biochemical and spectroscopic techniques to gain insight into its mode of action. The biomimetic effort will focus on generating and trapping metastable species that relate to diiron(III)-peroxo and high-valent iron intermediates observed in the redox cycles of the nonheme diiron enzymes. Of particular interest are complexes with unusual Fe(III)-O-Fe(IV) and Fe(IV)-O-Fe(IV) units, motifs associated with the oxidizing species formed during enzyme catalysis. These novel complexes will be characterized by a variety of spectroscopic techniques to determine their structures and electronic properties. Corresponding complexes with Fe(III)-O-Mn(IV) and Fe(IV)-O-Mn(IV) units will also be synthesized to model high-valent intermediates associated with the recently discovered ribonucleotide reductase (RNR) with a FeMn active site (instead of a diiron site) from the parasite Chlamydia trachomatis. Understanding the difference in the reactivity properties of high-valent FeFe and FeMn complexes may contribute to the development of better methods for treating infections from such human pathogens. Nonheme diiron enzymes perform a variety of metabolically critical functions that require O2. For example, ribonucleotide reductase is a key enzyme that controls DNA biosynthesis, while deoxyhypusine hydroxylase is required for the formation of mature eukaryotic initiation factor 5a that is essential for cell proliferation. Understanding how these enzymes work can lead to the development of new drug strategies for treating cancer, AIDS, and infections of human pathogens like chlamydiae.

Public Health Relevance

Nonheme diiron enzymes perform a variety of metabolically critical functions that require O2. For example, ribonucleotide reductase is a key enzyme that controls DNA biosynthesis, while deoxyhypusine hydroxylase is required for the formation of mature eukaryotic initiation factor 5a that is essential for cell proliferation. Understanding how these enzymes work can lead to the development of new drug strategies for treating cancer, AIDS, and infections of human pathogens like chlamydiae.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM038767-26
Application #
8447043
Study Section
Macromolecular Structure and Function A Study Section (MSFA)
Program Officer
Anderson, Vernon
Project Start
1999-04-01
Project End
2015-03-31
Budget Start
2013-04-01
Budget End
2014-03-31
Support Year
26
Fiscal Year
2013
Total Cost
$300,915
Indirect Cost
$88,615
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
Zhou, Ang; Crossland, Patrick M; Draksharapu, Apparao et al. (2018) Oxoiron(IV) complexes as synthons for the assembly of heterobimetallic centers such as the Fe/Mn active site of Class Ic ribonucleotide reductases. J Biol Inorg Chem 23:155-165
Jasniewski, Andrew J; Que Jr, Lawrence (2018) Dioxygen Activation by Nonheme Diiron Enzymes: Diverse Dioxygen Adducts, High-Valent Intermediates, and Related Model Complexes. Chem Rev 118:2554-2592
Magherusan, Adriana M; Zhou, Ang; Farquhar, Erik R et al. (2018) Mimicking Class?I?b Mn2 -Ribonucleotide Reductase: A MnII2 Complex and Its Reaction with Superoxide. Angew Chem Int Ed Engl 57:918-922
Kal, Subhasree; Draksharapu, Apparao; Que Jr, Lawrence (2018) Sc3+ (or HClO4) Activation of a Nonheme FeIII-OOH Intermediate for the Rapid Hydroxylation of Cyclohexane and Benzene. J Am Chem Soc 140:5798-5804
Fan, Ruixi; Serrano-Plana, Joan; Oloo, Williamson N et al. (2018) Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV-Oxo Intermediate. J Am Chem Soc 140:3916-3928
Komor, Anna J; Jasniewski, Andrew J; Que, Lawrence et al. (2018) Diiron monooxygenases in natural product biosynthesis. Nat Prod Rep 35:646-659
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
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
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

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