Independent Minds, Working Together

Dean Fraga

Biochemistry & Molecular Biology

Project Description: How do proteins evolve new functions?

This project combines biology and chemistry to answer questions concerning the evolution of protein structure and function. This project is part of a larger interdisciplinary collaboration between Dr. Dean Fraga in Biology and Drs. Paul Edmiston and Mark Snider in Chemistry. Together we are trying to understand the biochemical and evolutionary details of the phosphagen kinases, specifically creatine and arginine kinases. We use a combination of molecular biology, evolutionary methods, biochemistry, and physical chemistry to better understand how proteins acquire novel functions. Our current model system is the phosphagen kinase family.

Phosphagen kinases (PK) are highly conserved proteins that function in energy homeostasis by maintaining stable ATP concentrations during times of high demand, such as seen in nerve or muscle cells. In humans the relevant phosphagen kinase is creatine kinase, which uses creatine as its substrate for creating creatine phosphate, a high energy molecule. Other species use different phosphate accepting guanidine containing substrates such as arginine, or glycocyamine. In all cases the phosphagen is a form of stored energy that helps the cells respond quickly to replenish ATP levels when they are drawn down by metabolic demands.

Our goal with this project is to document a "molecular-fossil record' of transition states in protein evolutionary history. Specifically, how has the protein evolved such that there are forms that bind different substrates and others that are have different quaternary structures (such as monomers versus dimers). We are trying to determine how protein evolves from one state to another through mutations. A student working on this project would gain experience with molecular genetics (cloning and site-directed mutagenesis), protein purification, enzyme analysis, and physical biochemistry techniques (binding energy measurements through isothermal calorimetry (ITC)).