X-ray Crystallography and Biophysical Characterization of
Soluble and Membrane Proteins

Our research investigates the three-dimensional structure and molecular mechanism of membrane proteins central to health and disease using crystallographic methods. Membrane proteins constitute roughly a third of cellular proteins, but our understanding of their three-dimensional structure and function has lagged due to technical difficulties in their expression, purification, and crystallization. We seek to answer questions relating to the structural rearrangements in membrane proteins that accompany and facilitate signal transmission across the cell membrane and the importance of oligomerization and multi-molecular complex formation in the function of integral and peripheral membrane proteins. We primarily are investigating proteins that mediate host-pathogen interactions involving the human immune system by employing X-ray crystallography to determine high-resolution structures of virulence factors from pathogenic bacteria.  We are studying effectors that transform benign environmental bacteria into dangerous human pathogens. Our efforts have recently focused on a fascinating class of deliverable membrane proteins called pore-forming toxins. These factors are secreted as soluble proteins, but assemble into oligomeric transmembrane pores that kill host target cells. By solving toxin structures in water-soluble and fully assembled integral membrane states, we seek details about the mechanism and specificity of these agents against human cells. This information will not only provide insight into the pathology of opportunistic human pathogens, but also aid in the engineering of pore-forming toxins for a host of therapeutic and biotechnological applications. These studies seek to delineate the structural underpinnings that allow membrane proteins to accomplish a wide range of important cellular functions.