Understanding the Behaviors of Soluble Penicillin-Binding Proteins 5 And 6 in Escherichia coli

Abstract

Escherichia coli (E. coli) has four known DD-carboxypeptidases (DD-CPases), namely penicillin-binding protein (PBP) 4, 5, 6, and DacD, and are thought to restrict the unwanted crosslink formation between the nascent peptidoglycan strands. So far, the in vivo functions of these enzymes are mostly unknown, except for PBP 5, which helps maintain cell shape. In spite of high degree of identity, PBP 6 is unable to imitate the shape maintaining activity of PBP 5. A 20 amino acids (aa) segment near to the KTG motif forms the morphology maintenance domain (MMD) in PBP 5 and the replacement of the corresponding amino acids of PBP 6 with that of PBP 5 MMD restores normal morphology in E. coli.