Multiple mechanisms of membrane anchoring of Escherichia coli penicillin-binding proteins

Abstract

The major penicillin-binding proteins (PBPs) of Escherichia coli play vital roles in cell wall biosynthesis and are located in the inner membrane. The high M r PBPs 1A, 1B, 2 and 3 are essential bifunctional transglycosylases/transpeptidases which are thought to be type II integral inner membrane proteins with their C-terminal enzymatic domains projecting into the periplasm. The low M r PBP4 is a DD-carboxypeptidase/endopeptidase, whereas PBPs 5 and are DD-carboxypeptidases. All three low M r , PBPs act in the modification of peptidoglycan to allow expansion of the sacculus and are thought to be periplasmic proteins attached with varying affinities to the inner membrane via C-terminal amphiphilic α-helices. It is possible that the PBPs and other inner membrane proteins form a peptidoglycan synthesizing complex to coordinate their activities.