Elucidation of Substrate Binding to Photolyase from Sulfolobus solfataricus Using Isothermal Titration Calorimetry

DNA photolyase is a DNA repair enzyme commonly found across the kingdom of life. Binding studies for the hyperthermophilic photolyase derived from Sulfolobus solfataricus (SsPL) may serve to illuminate how DNA photolyase can adapt over a large temperature range. In the first section of this study, the thermodynamics of substrate binding for SsPL in a choline chloride buffer were determined using isothermal titration calorimetry. Using the Counter-Ion Condensation Concept as a model, ionic strength studies were performed to separate the binding interactions into electrostatic, and nonelectrostatic components. The electrostatic interactions do not appear to make a significant contribution to the thermodynamic binding parameters. The second part of this study will be a review of how the sugar trehalose contributes to stabilization of proteins, such as photolyase, at high temperatures. The experimental set up for binding studies involving SsPL in trehalose will be included, and preliminary binding data will be obtained. The trehalose review will serve as an introduction to forthcoming binding studies involving SsPL in the presence of trehalose