Kinetics of Ligand Interaction, Substrate Turnover and Oxime Reactivation in Cholinesterases
Skaggs School of Pharmacy and Pharmaceutical Sciences
University of Zagreb, Zagreb, Croatia
Dr. Radić is a graduate of the University of Zagreb in Croatia where he started his research in acetylcholinesterase (AChE) reaction kinetics under mentorship of late Dr. Elsa Reiner, one of founding contributors in the field of cholinesterases. His interests in molecular structure of AChE brought him to UC San Diego where as a post-doc in the Palmer Taylor group he contributed to functional mapping of the AChE molecule using site directed mutagenesis and defined structural domains and amino acid residues critical for catalytic activity and ligand interaction. He proposed common, simplified kinetic scheme and equation to describe acetylcholine (ACh) turnover by both AChE and its structurally and functionally close relative butyrylcholinesterase (BChE) that included both substrate inhibition of AChE and substrate activation of BChE, two prominent forms of deviation from Michaelis-Menten kinetics. Dr. Radić developed intrinsic tryptophan fluorescence-based assays for in vitro monitoring of time resolved and equilibrium-based interactions of cholinergic ligands with native nicotinic acetylcholine receptor ligand binding domain surrogates, ACh binding proteins (AChBPs), as well as with AChE and BChE. This assay proved essential in functional characterization of one of tightest known, small molecule femtomolar inhibitors of AChE developed in collaboration with Dr. Barry Sharpless of The Scripps Research Institute in La Jolla (TSRI). Dr. Radić led and leads, as a PI, NIH funded national and international collaborative projects with researchers from TSRI, Oak Ridge National Laboratory (Dr. Andrey Kovalevsky), University of Utah at Salt Lake City (Dr. Donald Blumenthal), The Ohio State University (Dr. Xiaolin Cheng), UC San Diego (Dr. Carlo Ballatore), New York Structural Biology Center (Dr. Jonah Cheung), Institute for Medical Research and Occupational Health in Zagreb, Croatia (Dr. Zrinka Kovarik), University of Hradec Kralovy, Czech Republic (Dr. Kamil Kuča), University Hospital Hradec Kralovy (Dr. Ondrej Soukup and Dr. Jan Korabecny), towards development of novel, improved oxime reactivators of OP-AChE and OP-BChE conjugates, both in vitro and in vivo.
Education: B.Sc., M.Sc. and Ph.D. in Chemistry and in Biochemistry from University of Zagreb, Croatia.
Awards and Honors: 2016 Spiridion Brusina Medal; IREX Graduate Student Fellow and Fulbright and Fogarty Postdoctoral Research Fellow at UCSD, La Jolla. Fulbright fellow host.
Leadership Experience: Treasurer, Croatian Society of Biochemistry and Molecular Biology (1990).
- Manipulations of Drug-Macromolecule Structural Interactions (SSPPS elective)
- Visualization of macromolecules and their interactions with drugs in 3D (WARR 87);
- Enzymes: Kinetics and Reaction Mechanisms, (graduate course at University of Zagreb)
- Led development of a new course of "smart" bis-oxime antidotes against OP intoxication.
- Outlined joint simplified kinetic scheme and model for substrate turnover by AChE and BChE.
- Developed intrinsic tryptophan based assay for in vitro characterization of ligand interaction with AChBP, AChE and BChE.
- Described allosteric modulation of oxime reactivation of OP-BChE conjugates as a basis for development of a new class of small molecule measures to counteract OP poisoning and improve associated therapy.
- Luedtke S et al. (2021). Backbone Conformation Shifts in X-ray Structures of Human Acetylcholinesterase upon Covalent Organophosphate Inhibition. Crystals 11: 1270.
- Gerlits O et al. (2021). Room temperature crystallography of human acetylcholinesterase bound to a substrate analogue 4K-TMA: Towards a neutron structure. Curr. Res. Struct. Biol. 3: 206-215.
- Blumenthal D et al. (2021). Covalent inhibition of hAChE by organophosphates causes homodimer dissociation through long-range allosteric effects. J. Biol. Chem. 297: 101007.
Drug discovery for therapy of OP intoxication.