The broad purpose of this research program is to determine the fundamental relationships between the structures of active sites in metalloproteins and function. This collaborative supplement application builds on the existing research efforts in Hydrogen Bonding Cavity Motifs about Metal Ions (2 Ro1 GM050781-21) by offering a new approach that combines both synthetic and biological chemistries with molecular biology to create artificial metalloproteins that control the microenvironments (secondary coordination sphere) surrounding metal ions. Protein hosts streptavidin and avidin serve as new binding sites for synthetic metal complexes: these proteins do not normally bind metal ions but have an unusually high affinity for biotin (Ka ~ 1013 M-1). This specific binding will be used to direct biotinylated synthetic metal complexes to specific locations within the proteins. The protein hosts will control the microenvironments around the metal complexes through non-covalent interactions, particularly hydrogen bonds (H-bonds). The strength of this integrated approach is the ability to independently tune the properties of the artificial metal cofactors (through chemical methods) and the hosts (through molecular biology methods) to readily provide information on essential structure-function relationships. The combined chemical and genetic (chemogenetic) approach allows access to a diverse group of artificial metalloproteins that can directly address questions on how active site structures create specific H-bonding networks about metal ions. Our approach allows for the confinements of two distinct metal complexes at fixed (but close) locations within the proteins, as the secondary coordination sphere is systematically modulated. We can thus explore how differences in metal-metal distances and H-bonding networks affect dioxygen binding and activation, including detecting high-energy transients that are often difficult to observe. Long-term goals include developing structure function relationships in metal-assisted oxidative catalysis. Metalloproteins perform functions not yet achieved in other types of systems, including artificial metalloproteins. Our hypothesis is that the lack of control of the secondary coordination sphere is a major obstacle to desired functions. Results from structural biology show that non-covalent interactions within the secondary coordination spheres of metalloproteins are instrumental in regulating function. Therefore the function and dysfunction of health-related metalloproteins can be understood in the context of changes in their microenvironments. It is still unclear, even in biomolecules, how non-covalent interactions are able to influence metal-mediated processes. Investigations into these effects require basic structural, functional, and mechanistic studies in which the effects of individual components can be analyzed separately. We propose a new chemogenetic approach whereby site-specific modulations in structure of the protein host and synthetic metal complex can be readily accomplished, in order to establish correlations with function? these types of studies will lead to fundamental insights into biochemical processes. Ultimately, this research will provide insights into the properties of biological catalysts and lead to new classes of artificial catalysts that incorporate the exquisite control of reactivity characteristic of metalloenzymes.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
3R01GM050781-21S1
Application #
8662429
Study Section
Program Officer
Anderson, Vernon
Project Start
1994-04-01
Project End
2015-12-31
Budget Start
2013-01-01
Budget End
2013-12-31
Support Year
21
Fiscal Year
2013
Total Cost
$43,329
Indirect Cost
$13,329
Name
University of California Irvine
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
046705849
City
Irvine
State
CA
Country
United States
Zip Code
92697
Cook, Sarah A; Ziller, Joseph W; Borovik, A S (2014) Iron(II) complexes supported by sulfonamido tripodal ligands: endogenous versus exogenous substrate oxidation. Inorg Chem 53:11029-35
Sickerman, Nathaniel S; Peterson, Sonja M; Ziller, Joseph W et al. (2014) Synthesis, structure and reactivity of Fe(II/III)-NH3 complexes bearing a tripodal sulfonamido ligand. Chem Commun (Camb) 50:2515-7
Usharani, Dandamudi; Lacy, David C; Borovik, A S et al. (2013) Dichotomous hydrogen atom transfer vs proton-coupled electron transfer during activation of X-H bonds (X = C, N, O) by nonheme iron-oxo complexes of variable basicity. J Am Chem Soc 135:17090-104
Park, Young Jun; Cook, Sarah A; Sickerman, Nathaniel S et al. (2013) Heterobimetallic Complexes with M(III)-(*-OH)-M(II) Cores (M(III) = Fe, Mn, Ga; M(II) = Ca, Sr, and Ba): Structural, Kinetic, and Redox Properties. Chem Sci 4:717-726
Cook, Sarah A; Borovik, A S (2013) Inorganic chemistry: Deconstructing water oxidation. Nat Chem 5:259-60
Gupta, Rupal; Taguchi, Taketo; Borovik, A S et al. (2013) Characterization of monomeric Mn(II/III/IV)-hydroxo complexes from X- and Q-band dual mode electron paramagnetic resonance (EPR) spectroscopy. Inorg Chem 52:12568-75
Sano, Yohei; Weitz, Andrew C; Ziller, Joseph W et al. (2013) Unsymmetrical bimetallic complexes with M(II)-(*-OH)-M(III) cores (M(II)M(III) = Fe(II)Fe(III), Mn(II)Fe(III), Mn(II)Mn(III)): structural, magnetic, and redox properties. Inorg Chem 52:10229-31
Park, Young Jun; Ziller, Joseph W; Borovik, A S (2011) The effects of redox-inactive metal ions on the activation of dioxygen: isolation and characterization of a heterobimetallic complex containing a Mn(III)-(?-OH)-Ca(II) core. J Am Chem Soc 133:9258-61
Stone, Kari L; Borovik, A S (2009) Lessons from nature: unraveling biological CH bond activation. Curr Opin Chem Biol 13:114-8
Parsell, Trenton H; Yang, Meng-Yin; Borovik, A S (2009) C-H bond cleavage with reductants: re-investigating the reactivity of monomeric Mn(III/IV)-oxo complexes and the role of oxo ligand basicity. J Am Chem Soc 131:2762-3

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