Comprised of 13-15 different proteins, the type II secretion system (T2SS) is one of at least seven unique secretions systems (T1SS - T6SS and T9SS) present in gram-negative bacteria. The T2SS mediates extracellular delivery of a variety of proteins conferring a survival advantage to pathogenic as well as environmental species. The T2SS has been identified in pathogens such as Vibrio cholerae, Pseudomonas aeruginosa, Legionella pneumophila, Escherichia coli O157, and more recently, Acinetobacter baumannii, where it is responsible for secretion of toxins and hydrolytic enzymes including proteases, lipases and carbohydrate-active enzymes. For our studies in the Sandkvist lab we use two different model systems: Vibrio cholerae, the causative agent of cholera, which is a life-threatening diarrheal disease endemic to many developing countries, and Acinetobacter baumannii, an opportunistic pathogen known for its persistence in hospital settings and multidrug resistance.
Structure and Function Analysis of the T2SS
One of the goals of our studies is to determine the architecture of the T2SS and the molecular mechanism of cargo sorting and secretion by this nanomachine. For this, we subject individual components as well as sub-complexes and cargo proteins to genetic, molecular, biochemical and structural characterization to define the interactions that drive secretion by the T2SS.
Proteomic and Activity Screens
The Sandkvist lab is also interested in determining the contribution of the T2SS to pathogenesis and environmental survival of V. cholerae and A. baumannii. Using a variety of proteomic techniques and enzyme activity screens we identify proteins that are specifically secreted via the T2SS during virulence-inducing conditions as well as during environmental growth conditions. The function of these proteins are then determined using in vivo and in vitro assays
High Throughput Screening Assays
To identify inhibitors of the T2SS, the Sandkvist lab is taking a high throughput small molecule screening approach followed by structure activity relationship analysis and optimization. This basic translational research will generate new tools to be used in studies of the mechanism of secretion. In addition, some of these inhibitory compounds may be developed into alternative therapies to combat antibiotic resistant infections caused by gram-negative species that depend on the T2SS for in vivo fitness and pathogenesis.