Tuberculosis (TB) exacts a significant, global toll on human health, accounting for more than nine million cases of clinical disease and 1.7 million deaths each year. Infections by the causative agent, Mycobacterium tuberculosis
are intractable, largely because the organism is not completely cleared by the immune system and persists in a latent state that can be reactivated. This is especially problematic in immunocompromised individuals such as those infected with HIV.
We are studying the molecular switches that trigger the changes in M. tuberculosis
that are suspected to lead to latency in collaboration with the laboratory of Dr. Robert Husson at Children's Hospital Boston/Harvard Medical School and Dr. Bryce Nickels at Rutgers University
is an important, emerging nosocomial pathogen in the United States. The transition from harmless colonization to disease is typically preceded by antimicrobial therapy, which presumably alters the balance of the intestinal flora, enabling C. difficile
to proliferate. One of the most perplexing aspects of the C. difficile
infectious cycle is its ability to survive antimicrobial therapy and transition from inert colonization to active infection. Clinical presentation of C. difficile
infection ranges from mild diarrhea to severe, debilitating complications including pseudomembranous colitis and toxic megacolon. Billions of health care dollars are spent on C. difficile
infection treatment in the United States annually, and costs are expected to escalate since the number of cases and severity of disease is steadily increasing. The emergence of the highly virulent BI/NAP1/027 (toxinotype III) strain accounts for some of this increase in severity and contributes to rising mortality rates. We are studying the molecular features that underlie C. difficile
pathogenesis and persistence after antibiotic exposure in collaboration with Dr. Thomas Kirn at UMDNJ-RWJMS
and Robert Wood Johnson University Hospital.
Despite serving essential roles in countless important biological processes ranging from receptor-mediated cell signaling to control of cell adhesion, our ability to fully understand the function of membrane proteins is severely hampered by their intrinsic biochemical properties and the low success rates for production using existing protein expression systems. Although structural analysis of proteins has traditionally served as an important complementary approach to classical genetic and biochemical methods for understanding protein function, membrane proteins have been profoundly intractable. In fact, although they constitute up to 30% of the total proteins encoded by genomes ranging from bacteria to humans, they represent less that 1% of the nearly 60,000 structures in the Protein Data Bank as of February 2010.
Specialized protein expression systems in bacteria and yeasts have been successfully implemented for efficient production of numerous soluble human, bacterial and eukaryotic proteins for use as biological reagents, as pharmaceuticals, as subunit vaccines or for structural analysis. Currently, bacterial expression systems are most commonly enlisted for structure studies using nuclear magnetic resonance (NMR) and X-ray crystallography. While the track record for expression of bacterial proteins using E. coli
-based expression systems has been impressive, the isolation of properly folded eukaryotic proteins (both soluble and membrane proteins) using these systems has been challenging, and there is significant room for improvement. We are designing and optimizing a novel protein expression system in order to enhance success rates for NMR structures from eukaryotic recombinant protein targets, including membrane proteins. The work is in collaboration with the laboratory of Gaetano Montelione at Rutgers University
, who is also the director of the Northeast Structural Genomics Consortium.