Experimental and Theoretical Studies of Charge-Charge Interactions in Proteins

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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 overall goal of this project is to explore the relation between the charge-charge interactions on the protein surface and properties of proteins such as stability, solubility and enzymatic activity. The experimental work will be performed with several model proteins (ubiquitin, CspB, CDC42) that differ in three dimensional structure, size, and functional activity. The amino acid sequence of these proteins will be altered according to the theoretical predictions based on different models for calculation of charge-charge interactions. The consequences of these changes in terms of stability, solubility and enzymatic activity will be measured using a variety of biophysical methods. 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.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. This research will also have broad impact on the research and education infrastructure because training of graduate and undergraduate students is an intrinsic aspect of all of the experimental and theoretical work. The scientific concepts derived from this work will be incorporated into graduate courses that are offered by the PI.