The Role of Conformational Dynamics of Beta-Lactamases in Conferring Antibiotic Resistance

The discovery of antibiotics was one of the greatest medical discoveries of the 20^th century. Infectious diseases were rampant prior to the discovery of antibiotics, which resulted in high morbidity and mortality rates. In fact, prior to the antibiotic revolution, the average life expectancy at birth in the United States was a mere 47 years. In comparison, today the average life expectancy at birth is 78 years, and the leading causes of death are no longer infectious diseases, but rather are due to non-communicable diseases such as cardiovascular disease and cancer. Antibiotics have been tremendously successful in increasing the quality and duration of human life, but we are currently in the midst of a health crisis threatening to take us back to the pre-antibiotic days. The rapid rise of antibiotic resistance coupled with the lack of novel antibiotics is therefore an immediate health concern.

β-Lactams are a class of antibiotics often referred to as broad-spectrum drugs because of their effectiveness in treating infections from multiple pathogens. The mechanism of action of these drugs is to inhibit Penicillin Binding Proteins (PBPs), which are necessary for bacterial cell wall synthesis. Antibiotic resistance towards β-lactams is often promoted via the production of β-lactamases that have the capability to hydrolyze the β-lactams, rendering them ineffective against their drug targets.

The focus of the research in this thesis is to further our understanding of how β-lactamases are evolving to provide resistance to β-lactams, with a specific focus on resistance towards carbapenems or “drugs of last resort”.X-Ray crystallography studies have been of utmost importance in unraveling how β-lactamases hydrolyze β-lactam substrates. The work in this thesis compliments the static view of β-lactamases given by X-ray crystallography with a dynamic perspective of β-lactamase activity given by the Nuclear Magnetic Resonance (NMR) studies presented here. NMR is well-suited for the study of β-lactamase activity because it is a non-invasive technique, reveals site-specific structural and dynamics information, and it can be utilized to study both the enzyme and substrate. By understanding the conformational dynamics of β-lactamases, we can potentially design novel, potent inhibitors to combat antibiotic resistance.