Penicillin-Binding Protein Transpeptidase Active Site (PBP Transpeptidase Active Site)

The transpeptidase domain within Penicillin-Binding Proteins (PBPs) is responsible for catalyzing the cross-linking of peptidoglycan chains, providing structural integrity to the bacterial cell wall. The active site, characterized by conserved motifs (SxxK, SxN, KTGT) and key residues (e.g., Ser294, Lys333, Asp447), is the primary target for β-lactam antibiotics. These antibiotics inhibit activity by covalently binding to the active-site serine, mimicking the natural substrate (D-Ala-D-Ala) and forming a stable acyl-enzyme complex, thus blocking cell wall synthesis and leading to bacterial death. Resistance can arise through mutations or low-affinity PBP variants.

Irreversible inhibition of transpeptidase activity via covalent binding to the active site serine residue, preventing peptidoglycan cross-linking.