Live Poster Session: Zoom Link
Thursday, July 30th 1:15-2:30pm EDT
Abstract: Heptosyltransferase I (HepI) dynamics are critical to successful addition of a heptose moiety to lipopolysaccharides, a component of the Gram-negative bacterial cell membrane. Without this addition, a truncated lipopolysaccharide is synthesized, and survival of bacteria treated with hydrophobic antibiotics decreases. Previous investigations, including tryptophan fluorescence studies, and molecular dynamics (MD) simulations, indicate that HepI undergoes a large-scale closing motion upon substrate binding. MD simulations characterizing enzyme interconversion between open and closed states identified negatively correlated motions between residues in flexible active site loops, and residues in the C-terminal domain. Mutagenesis of amino acids hypothesized to modulate chain flexibility within the C-terminal loops, increased HepI enzymatic efficiency, indicating that these dynamic regions play a role in the formation of the Michaelis complex. However, simulated dynamics of these mutants have not yet been studied. Root mean-square deviation, root mean-square fluctuation, and dynamic cross correlational analyses were performed and revealed that, with one exception, mutagenesis of these residues modified correlated motion between the N- and C-terminal domains, and eliminated the strong negatively correlated motions within the N-terminal domain. The findings support previous kinetic and simulation data indicating the importance of the dynamic modes of HepI, and contribute to the growing body of work seeking to characterize this enzyme with a view to increasing bacterial antibiotic sensitivity.
Vaishnaw_Exploring-Simulated-Molecular-Dynamics-Between-Heptosyltransferase-I-Domains-Maya-VaishnawLive Poster Session: Zoom Link
Thursday, July 30th 1:15-2:30pm EDT