All of the following statements about penicillin-binding proteins are true EXCEPT :

Beta-lactam antibiotics act by inhibiting the cross-linking of peptidoglycan chains in the bacterial cell wall. This action is carried out by transpeptidase enzyme. Transpeptidases and similar enzymes involved in cross-linking are called penicillin-binding proteins (PBPs). All beta-lactam antibiotics bind to PBPs and inhibit cell wall synthesis. The drugs in p-lactam category are: Penicillin Cephalosporins Carbapenems e.g imipenem Monobactam e.g. aztreonam Mutation in PBPs is an important cause of methicillin resistance in Staphylococcus aureus. Vancomycin does not bind to PBPs but acts by inhibiting transglycosylase.