Vince J. LiCata

Lewis S. Flowers Professor
Brij Mohan Distinguished Professor
Ph.D., Johns Hopkins University, 1990
Protein structure, function, and stability; extremophilic proteins, protein-DNA interactions.

licata@lsu.edu


LiCata Lab Homepage


Our laboratory studies proteins: most particularly protein-DNA and protein-ligand interactions, protein folding and stability, and protein structure and conformation in solution. Our work is primarily focused on the Type I DNA polymerases from Thermus aquaticus (Taq/Klentaq) and E. coli (Pol I/Klenow). The DNA polymerases from E. coli and T. aquaticus are a homologous mesophilic-thermophilic pair of proteins. Their molecular structures and basic catalytic functions are highly homologous, yet the Taq enzyme works near the boiling point of water, while the E. coli enzyme is irreversibly destroyed by exposure to 50oC. We directly and comparatively examine the DNA binding, protein folding, and global structural characteristics of these two species of DNA polymerases with the goal of delineating the exact differences and similarities between the two proteins in order to understand what features are necessary to achieve high temperature stability and activity for a DNA polymerase. These studies include characterizations of DNA binding using fluorescence anisotropy and titration calorimetry, characterizations of stability using thermal and chemical denaturation methods, and characterization of structural and conformational changes using small angle X-ray scattering, and analytical ultracentrifugation. We are also utilizing site-directed mutagenesis and directed evolution to elucidate the detailed structural features differentiating the two species of polymerase.

We also examine similar questions in other protein systems, including the mammalian adipocyte lipid binding protein (ALBP), and aspartate transcarbamylase. ALBP is found in high concentrations in adipose cells and macrophages, and has been strongly implicated in the development of Type 2 diabetes, obesity, and atherosclerosis. Our laboratory is studying the stability and lipid binding properties of ALBP, with emphasis on the control of these processes by protein surface electrostatics and environmental (solution) conditions. E. coli aspartate transcarbamylase (ATCase) is one of the most extensively studied enzymes in biochemistry. It has served, and continues to serve in our laboratory as a benchmark for different studies, particularly our analytical ultracentrifugation and small angle X-ray scattering structural studies.


Selected Recent Publications

Datta, K., Wowor, A.J., Richard, A.J., and LiCata, V.J., 2006, Temperature dependence and thermodynamics of Klenow polymerase binding to primed-template DNA, Biophys. J. 90: 1739-1751.

Richard, A.J., Liu, C.C., Klinger, A.L., Todd, M.J., Mezzasalma, T.M., and LiCata, V.J., 2006, Thermal stability landscape for Klenow DNA polymerase as a function of pH and salt concentration, Biochem. et. Biophys. Acta. 1764: 1546-1552.

LiCata, V.J., and Wowor, A.J., 2008, Applications of Fluorescence Anisotropy to the Study of Protein-DNA Interactions, Methods in Cell Biology, Vol. 84, 243-262.

Liu, C.-C., Richard, A.J., Datta, K., and LiCata, V.J., 2008, Temperature variable heat capacity effects in protein-DNA interactions, Biophys. J. 94: 3258-3265.

Liu, C.-C., Yang, Y., and LiCata, V.J., Origins of the thermostability of Taq DNA polymerase: entropy and denatured state size, submitted.

Datta, K., Johnson, N.P., LiCata, V.J., and von Hippel, P.H., Local conformations and competitive binding affinities of single- and double-stranded primer-template DNA at the polymerization and editing active sites of DNA polymerases, submitted.

 

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