Structural Biology/Biochemistry Seminar
Tuesday, April 1, 2014
Kasha Laboratory, Room 112
“Engineering Enzymatic Pericyclic Reactions.”
Dept. of Molecular Biosciences
University of Kansas
Host: Dr. Brian Miller
Structural and functional analysis of enzymes associated with iron uptake.
Pseudomonas aeruginosa is a ubiquitous, gram-negative bacterium that resides primarily in soil and water. Because of its prevalence in the environment, P. aeruginosa is a potentially dangerous opportunistic pathogen that is a common cause of infections in susceptible hosts, including burn patients, cancer patients undergoing chemotherapy, AIDS patients, those with immune deficiencies, and cystic fibrosis (CF) patients. P. aeruginosa is highly resistant to most antibiotics and therapeutics. The ability of these bacteria to develop antibiotic resistance is especially problematic for CF patients, which suffer from chronic infections, leading to debilitating lung damage and early mortality.
Iron is an essential element for almost all microorganisms, including P. aeruginosa. Because Fe(III) is very insoluble and frequently biologically inaccessible, many species of bacteria have developed elaborate systems to scavenge iron from their environment, including the human host where all the cellular iron is bound to proteins such as transferrin, lactoferrin, or hemoglobin. Siderophores are low molecular weight iron chelators produced by bacteria to scavenge iron from these low iron environments, and are frequently required for virulence. To survive and colonize human tissues, the bacteria must synthesize, secrete, and selectively take up the iron-loaded form of the siderophore. In the case of P. aeruginosa infections in CF patients, the siderophores remove iron from iron-containing proteins and enzymes of the lungs.
We are working to understand the biosynthesis of both siderophores produced by P. aeruginosa: pyochelin and pyoverdin. We propose that inhibitors to both pathways will be required, probably as a cocktail drug, for effective antibiotic therapy for P. aeruginosa infections. A detailed mechanistic understanding of enzyme targets is required for drug discovery in order to develop mechanistically tuned high-throughput screens and to further a rational basis for drug design. We use a highly integrated approach to inhibitor design, including kinetic analyses, mutagenesis, and x-ray crystallography