Elucidating allosteric signal disruption in PBP2a: impact of N146K/E150K mutations on ceftaroline resistance in methicillin-resistant Staphylococcus aureus

Ceftaroline (CFT) effectively combats methicillin-resistant Staphylococcus aureus (MRSA) by binding to the allosteric site on penicillin-binding protein 2a (PBP2a) and activating allosteric signals that remotely open the active pocket. However, the widespread clinical use of CFT has led to specific mutations, such as N146K/E150K, at the PBP2a allosteric site, which confers resistance to CFT in MRSA by disrupting the transmission of allosteric signals. Herein, computational simulations were employed to elucidate how the mutations disrupt the transmission of allosteric signals, thereby enhancing the resistance of MRSA to CFT. Specifically, the mutations alter the salt bridge network and electrostatic environment, resulting in a dynamic setting and decreased binding affinity of CFT within the allosteric pocket. Additionally, dynamical network analysis and the identification of allosteric pathways revealed that the reduced binding affinity diminishes the propagation of allosteric signals to the active site. Further evaluations demonstrated that this diminished signaling reduces the openness of the active pocket in the mutant systems, with "gatekeeper" residues and functional loops remaining partially closed. Redocking experiments confirmed that mutations lead to decreased docking scores and unfavorable docking poses for CFT within the active pocket. These findings highlight the complex interactions between structural changes induced by mutations and antibiotic resistance, providing crucial insights for developing new therapeutic strategies against MRSA resistance.