Penicillin-binding protein in Acinetobacter (PBP (specifically, PBP1A, PBP1B, PBP2, PBP3, PBP7/8 in *Acinetobacter baumannii*))

Penicillin-binding proteins (PBPs) in Acinetobacter, notably in *Acinetobacter baumannii*, are a family of essential enzymes located in the bacterial inner membrane responsible for the final stages of assembling and restructuring peptidoglycan, the major component of the bacterial cell wall[6][7]. PBPs possess transglycosylase and transpeptidase activities, allowing them to polymerize glycan chains and cross-link peptide subunits, thus conferring structural integrity and shape to the cell[1][2][3]. There are multiple PBPs in Acinetobacter, including PBP1A, PBP1B, PBP2, PBP3, and PBP7/8, each with specialized functions in growth, division, and morphology[7][4]. PBPs are the direct molecular targets of β-lactam antibiotics (including penicillins, cephalosporins, and carbapenems), which irreversibly acylate their active-site serine, blocking cell wall synthesis and leading to bacterial cell death[1][6]. Modifications in PBPs—such as mutational changes or altered expression—are key mechanisms behind β-lactam and carbapenem resistance in *A. baumannii*, a major clinical challenge because of the resulting multidrug resistance[6][7]. Some PBPs, like PBP2, possess unique structural features (such as zinc-binding sites) important for their stability and function; these sites may serve as new points for drug targeting[3]. PBPs also play indirect roles in resistance to non-β-lactam drugs (e.g., colistin) by interacting with other envelope components, highlighting their integrated role in cell envelope biology[5]. As such, PBPs in Acinetobacter are validated and important therapeutic targets for combating antibiotic-resistant infections[1][4][6].

Other names

PBPsabPBP2 (for *Acinetobacter baumannii* PBP2)PBP1A (ponA/mrcA)PBP1B (mrcB)PBP2 (pbpA/mrdA)PBP3 (ftsI)PBP7/8 (pbpG)

Inhibition of peptidoglycan cross-linking leading to cell lysis (by β-lactam antibiotics) Direct binding and inactivation by β-lactams at their active-site serine Altered or reduced affinity leads to antibiotic resistance