About

Interests

Biochemistry, Bio-Organic Chemistry, Medicinal Chemistry

Education

• BS. Chemistry and BA Biology, University of Toledo, Ohio, 1988
• PhD, The Pennsylvania State University, University Park, 1995
• Postdoctoral Research Associate, The Pennsylvania State University, University Park, 1995-1998

Research

We are interested in investigating and characterizing the reaction mechanism of metabolic enzymes essential for cellular functions such as protein turnover. These studies utilize techniques in molecular cloning and mutagenesis, basic organic synthesis, bioconjugation, protein purification, protein chemistry and enzyme kinetics. Results generated by in vitro studies are ancipitated to augment the in vivo characterization of the target enzyme to provide insight into the dynamics of its molecular mechanism in the cell. Ultimately, we hope to provide information that will contribute to a molecular understanding of diseases caused by defective metabolic enzymes.

Our current target enzyme is a serine protease (Lon) that requires ATP hydrolysis for protein degradation. Lon functions to regulate cellular protein turnover and is found in both eukaryotic and prokaryotic cells. In eukaryotes, Lon has an additional role in maintaining the functional integrity of mitochondria. Therefore, an understanding of Lon at the molecular and chemical level will significantly contribute to the understanding of certain mitochondria-related disease such as ocular myopathy as well as the development of anti-microbial agents using Lon as the target.

In our studies, we utilize the Escherichia coli system as a model system to investigate the reaction mechnaism of Lon. The proteolytic mechanism of Lon is being elucidated by steady-state enzyme kinetic methodologies, while the proteolytic and ATPase active sites are being mapped by bioconjugation and chemical modification techniques. In addition, structure and function correlation studies will be addressed by site-directed mutagenesis, and a cell-based assay will be used to assess the effect of various mutations on the in vivo function of Lon. Mechanistic information deduced from these studies will benefit further research efforts into unraveling the complex amino acid network linking proteolysis with ATP hydrolysis.

Selected Publications

• D. Vineyard, J. Patterson-Ward and I. Lee, “Single-turnover kinetic experiments confirm the existence of high- and low-affinity ATPase sites in Escherichia coli Lon Protease”, Biochemistry, in press (2006)
• X. Zhang, I. Lee, X. Zhou and A. J. Berdis, “Hydrophobicity, shape, and pi-electron contributions during translesion DNA synthesis”,JACS 128, 143-9 (2006)
• X. Zhang, I. Lee and A. J. Berdis, “A Potential Chemotherapeutic Strategy for the Selective Inhibition of Promutagenic DNA Synthesis by Nonnatural Nucleotides”, Biochemistry 44, 13111-10 (2005)
• X. Zhang, I. Lee and A. J. Berdis, “The use of nonnatural nucleotides to probe the contributions of shape complementarity and pi-electron surface area during DNA polymerization”, Biochemistry 44, 13101-10 (2005)
• D. Vineyard, J. Patterson, A. J. Berdis and I. Lee , “Monitoring the timing of ATP hydrolysis with activation of peptide cleavage in Lon by transient kinetics”, Biochemistry 44 , 1671-1682 (2005)
• I. Lee and A. J. Berdis, In Enzymes and Their Inhibitions: Drug Development ; H. J. Smith and C. Simon, Eds.; Chapter 2, Section 2: “Kinetics”, CRC Press LLC (2005)
• X. Zhang, I. Lee and A. J. Berdis, “Evaluating the Contributions of Desolvation and Base-Stacking During Translesion DNA Synthesis”,Organic & Biomolecular Chemistry 2, 1703-1711 (2004)
• T. Liu, B. Lu, I. Lee , G. Ondrovicoya, E. Kutejova and C. K. Suzuki, ” DNA and RNA binding by the mitochondrial Lon protease is regulated by nucleotide and protein substrates”, J Biol Chem. 279,13902-10 (2004)
• J. Patterson, D. Vineyard, J. Thomas-Wohlever, R. Behshad, M. Burke and I. Lee, “Correlation of an adenine-specific conformational change with the ATP-dependent peptidase activity of Escherichia coli Lon”, 43, 7432-42 (2004)
• B. Lu, T. Liu, J. A. Crosby, J. Thomas -Wohlever, I. Lee and C. K. Suzuki, “The ATP-Dependent Lon Protease of Mus Musculus is a DNA-binding protein that is functionally conserved between yeasts and mammals”, Gene 306, 45-55 (2003).
• J. Thomas-Wohlever and I. Lee, “Kinetic Characterization of the Peptidase Activity of Escherichia coli Lon Reveals the Mechanistic Similarities in ATP-dependent Hydrolysis of Peptide and Protein Substrates”, Biochem. 41, 9418-25 (2002)
• I. Lee and A. J. Berdis, “ATP-Dependent Degradtion of a Fluorescent lambda N Substrate-Mimic by Lon Protease.” Anal. Biochem.291,74-83 (2001)
• I. Lee, and S.J. Benkovic, “Catalytic Antibodies,”in Encyclopedia of Immunology (2nd ed.) (P.J. Delves and I.M. Roitt Eds.) Academic Press Ltd, London pp. 438-444 (1998).
• A. J. Berdis, I. Lee, J. K. Coward, C. Stephens, R. Wright, L. Schapiro and S. J. Benkovic, “A Cell-Cycle Regulated Adenine DNA Methyltransferase from Caulobacter crescentus Processively Methylates GANTC Sites on Hemimethylated DNA.”, Proc. Natl. Acad. Sci. (USA) 95, 2874 -2879 (1998)
• I. Lee, J. Stewart, W. Zhong and S. J. Benkovic, ” A Chemiluminescent Immunoassay for the Identification of Functional Single-Chain Antibodies.” Anal. Biochem. 230, 62-67 (1995)
• J. D. Stewart, I. Lee, B. A. Posner and S.J. Benkovic, ” The Expression of Properly-Folded Catalytic Antibodies in Escherichia coli.”Methods in Enzymol. 249, 507-519 (1995)
• C. Brummel, I. Lee, Y. Zhou, S. J. Benkovic and N. Winograd, “A Solution to the Address Problem of Combinatorial Libraries.” Science264, 399-402 (1994).

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