The affinity of imipenem (N-formimidoylthienamycin) for the penicillin-binding proteins of Staphylococcus aureus--binding and release.

Penicillin-binding proteins 1, 2 and 3 in Staphylococcus aureus were found to possess common properties. All have very strong affinities for both benzylpenicillin and imipenem (N-formimidoylthienamycin), and all have an activity which releases bound imipenem, but not bound benzylpenicillin. Lower molecular weight penicillin-binding protein 4, which has a rather weak affinity for benzylpenicillin and also weak penicillinase activity showed an extraordinarily high affinity for imipenem but no antibiotic-releasing activity.