Using Structural Studies to Investigate the Relationships Between Enzymes and Ligands.

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My research is focused on using protein structures to understand how molecules recognize each other in biological systems. My lab has established its reputation by using structural studies to enhance understanding of the interactions between enzymes and their substrates. This allows us to predict the effects that changes in the interactions will have on enzymes. Combining crystallography with enzymology, computational studies, and other biophysical techniques, we can characterize the ways that ligands interact with proteins. We have the long-term goal of using this information to develop compounds that can affect enzyme processes and to understand the evolution of enzyme systems. We are using the thioredoxin system as a model system for studying protein-protein interactions. The thioredoxin system is a critical system in oxidative stress. Our studies have increased our understanding of the interactions between thioredoxin (Trx) and thioredoxin reductase (TrxR). We predict that we can design peptides that exhibit specificity towards TrxR or Trx. Structural studies, enzymology, and other techniques to monitor protein-peptide binding (eg ITC and SPR) will help improve peptide binding. Understanding the evolution of enzyme structure-function relationships remains a key focus of my lab. We will continue to use the thioredoxin system to continue to study the way Trx and TrxR interact under extreme conditions. We have chosen this system because the chemistry is very well characterized, the Trx system is ubiquitous and oxidative stress is of great scientific interest. Using crystallography and enzymology we will further characterize the interactions of the thioredoxin system of extremophiles. A full understanding of the interactions that determine the recognition and binding of the TrxR/Trx complex will offer insights into other protein-protein interactions. Our work also involves understanding how small molecules are recognized by enzymes and how this binding affects enzyme behavior. Dihydrodipicolinate synthase(DHDPS) is regulated by lysine at an allosteric site. We have determined structures of DHDPS in the presence and absence of substrates and inhibitors, to study how the allosteric inhibition of this enzyme occurs. Our hypothesis is that inhibitor-induced changes in flexibility are responsible for the loss in activity. We will use bioinformatics, enzymology, and molecular dynamic studies to target specific amino acids to probe the flexible/rigid regions in controlling allosteric inhibition. These studies will greatly increase our knowledge in how flexibility changes affect the behavior of enzymes. Our access to state-of-the-art facilities, including the CVS, the SSSC, and the PCCF located at the University of Saskatchewan enables us to be leaders in studying protein structure-function relationships and over the next five years we will continue to investigate novel systems to address important questions about protein:ligand interactions.