Figure 6. Schematic representation of peptidoglycan biosynthesis and mechanisms of vancomycin action (A) and resistance (B).
Panel A depicts normal peptidoglycan production and shows that binding of the antibiotic to the terminal D-Ala-D-Ala of the peptidoglycan precursors prevents transpeptidation and transglycosylation, interrupting cell wall synthesis and resulting in bacterial death. Panel B shows the change in peptidoglycan synthesis produced by the expression of the vanA gene cluster. Change of the terminal dipeptide from D-Ala-D-Ala to D-Ala-D-Lac markedly reduces the binding of vancomycin to the peptidoglycan target permitting cell wall synthesis to continue.