Experimental and Theoretical Studies of Charge-Charge Interactions in Proteins

Pennsylvania State Univ University Park, University Park PA

Investigators

Abstract

Understanding the mechanisms of stabilization of protein structure represents one of the major aspects of the protein folding problem. The contributions of various short-range interactions, such as hydrogen bonding, the hydrophobic effect, and configurational entropy, to protein stability have been well documented. However, it is becoming more and more evident that the long-range electrostatic interactions between charged protein groups are also important contributors to protein structure and stability. The proposed work has an overall goal to explore the relation between the charge-charge interactions on the protein surface and the protein stability by engineering a thermostable protein by redesigning the charge-charge interactions on the protein surface, and analyzing the optimized charge-charge interactions. The theoretical part of the work is based on the calculation of the charge-charge interactions in proteins using Tanford-Kirkwood approach with Bashford-Karplus approximation (TK-BK procedure). The experimental measurement of the stabilities of the protein variants designed using TK-BK predictions will be done using differential scanning calorimetry, or using chemical (urea) induced denaturation monitored by the changes in the circular dichroism or fluorescence intensity properties. The fundamental importance of this research is that using a combination of theoretical calculations and experimental measurements the relationship between charge-charge interactions and the protein stability will be explored. From the practical point this research will provide the foundation for the design of proteins stable at extreme temperatures. This will benefit the industrial use of proteins where thermostability of enzymes is in many cases the largest obstacle.