Bacterial penicillin-binding protein (PBP)

Bacterial penicillin-binding proteins (PBPs) are a group of enzymes essential for the synthesis and maintenance of the bacterial cell wall. They catalyze the transglycosylation and transpeptidation reactions necessary for cross-linking peptidoglycan strands, providing the cell with mechanical strength and shape (UniProt, 2024). PBPs are categorized into high-molecular-weight and low-molecular-weight classes based on their domain structure and specific enzymatic roles in cell division and elongation (PubMed, 2022). These proteins serve as the primary molecular targets for beta-lactam antibiotics, such as flucloxacillin, which act as substrate analogs to inhibit cell wall assembly. Flucloxacillin specifically targets PBPs in Gram-positive bacteria, including penicillinase-producing Staphylococcus aureus, by forming a stable covalent bond with the enzyme's active site (StatPearls, 2023). This inhibition leads to the accumulation of peptidoglycan precursors and triggers autolytic enzymes, ultimately resulting in bacterial cell lysis and death. Clinical resistance often arises through the acquisition of alternative PBPs, like PBP2a, which have low affinity for most beta-lactam drugs (NIH, 2021). Consequently, PBPs remain a focal point for antibiotic research and the development of next-generation antimicrobial therapies.

Other names

Penicillin-binding proteinsPBPsDD-transpeptidaseD-alanyl-D-alanine carboxypeptidasePeptidoglycan glycosyltransferaseMurein transpeptidase

Flucloxacillin and other beta-lactam antibiotics act as structural analogs of the D-alanyl-D-alanine terminus of peptidoglycan precursors. They bind covalently to the active site of penicillin-binding proteins (PBPs), irreversibly inhibiting the transpeptidation reaction required for cross-linking peptidoglycan chains. This disruption weakens the bacterial cell wall, leading to osmotic lysis and cell death (StatPearls, 2023; PubChem, 2024).