Bifunctional Penicillin-Binding Proteins: Focus on the Glycosyltransferase Domain and its Specific Inhibitor Moenomycin

Beta-lactams and glycopeptides antibiotics directed against enzymes involved in bacterial cell wall synthesis have generated bacterial resistance. Search for new antibiotic molecules is widely focused on bifunctional Penicillin-Binding Proteins (PBPs), with particular emphasis on their glycosyltransferase activity. This function catalyzes glycan chain polymerization of the cell wall peptidoglycan. This review summarizes recent results about biochemical characterization of bifunctional PBPs and enzymatic properties of the glycosyltransferase domain. Moenomycin, a well studied glycosyltransferase activity inhibitor has provided useful informations about lipid binding properties and about cellular role of bifunctional PBPs. These enzymes were shown to be a part of the multienzymatic complex involved in peptidoglycan biosynthesis. Furthermore, bifunctional PBPs are also present in the protein complex located at the site of septation during cell division. The glycosyltransferase domain of bifunctional PBPs remains unsufficently characterized: the structural analysis may lead to the development of novel antibacterials and to the understanding of the enzymatic properties, while genetic and cellular studies focused on bifunctional PBPs will provide a wealth of knowledge regarding cell growth and division.