Open Collections

Bon, Christopher Giovanni

University of British Columbia

Staphylococcus aureus is a common pathogen that causes a widespread array of nosocomial and community infections, and whose pathogenicity and predisposition for developing a repertoire of antimicrobial resistances makes it of great clinical concern. The commonly used ß-lactam class of antibiotics target the penicillin-binding proteins (PBPs) of bacteria and inhibit proper bacterial cell wall synthesis to cause a cascade of effects that lead to cell death. S. aureus PBP1 is involved in building and septation of the bacterial cell wall during division and its presence is essential for survival of both antibiotic susceptible and resistant strains of S. aureus. PBP1 is the only S. aureus PBP that has yet to be comprehensively characterized, structurally or kinetically, in a ß-lactam inhibited form. Here, we present X-ray crystallographic data at 1.95-2.4 Å resolution for S. aureus PBP1 in its apo form as well as three acyl-enzyme structures for three classes of ß-lactam antibiotics: oxacillin, ertapenem and cephalexin for the penicillin, carbapenem, and cephalosporin classes respectively. PBP1 adopts the canonical domain folds of class b PBPs, with the active site located in a cleft in the transpeptidase domain that contains the three conserved motifs – SxxK, SxN, KTGT – necessary for catalysis. Our structural data suggests that the PBP1 active stie is accessible for substrate, with little conformational change in key structural elements required for its mechanistic action on ß-lactam inhibitors. Kinetic analysis via stopped flow and gel-based competition techniques further supports this ready acylation, with even the weakest preforming ß-lactams still having comparatively high reactivity for PBP1. Our structural and kinetic analyses shed insight into the ligand-PBP interactions that drive antibiotic efficacy against these historically critical antimicrobial targets and expands on current knowledge for potential future drug design for treatment against S. aureus infections.

Text

2024-07-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/80586

Biochemistry and Molecular Biology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/