Chemoproteomics unveils the antibacterial mechanism of silver ions: inhibiting peptidoglycan synthesis via targeting Mur family proteins in Staphylococcus aureus.

Silver ions (Ag+) have long been employed as natural antimicrobial agents, yet their precise mechanism of action remains unclear. In this study, we show that Ag+ displays strong antibacterial activity against Staphylococcus aureus (S. aureus), including methicillin-resistant strains (MRSA). Using chemoproteomic analysis, we identified MurB, MurC, and MurD as direct coordinate covalent targets of Ag+ in S. aureus, with binding occurring at cysteine residues Cys224, Cys368, and Cys221, respectively. This interaction leads to a reduction in MurB and MurD expression and inhibits MurC enzymatic activity, ultimately disrupting peptidoglycan synthesis and compromising bacterial cell wall integrity. Consequently, Ag+ treatment results in bacterial membrane leakage, altered membrane potential, and inhibited biofilm formation. Additionally, Ag+ reduces bacterial adhesion and invasion, alleviating the inflammatory response in host cells. Notably, Ag+ exhibits a low resistance frequency compared to conventional antibiotics, underscoring its potential as an effective antimicrobial agent. Its distinct mechanism of action and reduced likelihood of resistance development indicate that it may serve not only as an effective therapeutic strategy, but also as a probe for elucidating the mechanism of bacterial peptidoglycan biosynthesis. These results offer new insights for the development of antibiotics targeting Mur family proteins.