Pentaglycine cross-bridge in staphylococcal peptidoglycan

The **pentaglycine cross-bridge** is a distinctive structural feature of the peptidoglycan layer in staphylococcal species, particularly *Staphylococcus aureus*. It consists of five glycine residues (Gly₅) forming a bridge that covalently links the stem peptides of adjacent glycan chains, providing extensive cross-linking and mechanical strength to the bacterial cell wall[3][5][6]. Synthesis of this bridge depends on the sequential activity of the FemXAB protein family: FemX adds the first glycine, FemA and FemB add the remaining glycines[10]. The pentaglycine cross-bridge is essential for cell viability, cell shape maintenance, and resistance to osmotic lysis[3][5][10]. It serves as a docking site for certain bacteriolytic enzymes such as lysostaphin, which recognize and cleave this motif, leading to rapid cell death of staphylococci[1][4][7]. Disruption or loss of the pentaglycine bridge markedly weakens the cell wall, reduces methicillin resistance, impairs protein anchoring, and attenuates virulence[2][5][10]. Its specific presence in staphylococci makes the pentaglycine cross-bridge both a unique bacterial marker and a therapeutic target for new antistaphylococcal agents.

Other names

pentaglycine bridgeoligoglycine cross-bridgepentaglycine interpeptide bridgeGly₅ bridgepeptidoglycan interpeptide cross-link

Enzymatic cleavage (e.g., lysostaphin cleaves the pentaglycine bridge, causing rapid cell lysis); Inhibition of cross-bridge biosynthesis (FemXAB pathway enzymes are responsible for bridge assembly; inhibition is lethal); Antibiotic targeting (β-lactams and glycopeptides hinder peptidoglycan cross-linking and thus disrupt cell wall integrity)