Dalfopristin is an olefinic macrolactone that binds to the 50S subunit of the prokaryotic ribosome and interferes with the function of peptidyl transferase, thereby inactivating the donor and acceptor sites of the ribosome.
Unlike erythromycin-A (which interacts with bacterial 23S ribosomal RNA by contacts limited to hairpin 35 in domain II of the ribosomal RNA and to the peptidyl transferase loop in domain [V.sup.49]), telithromycin is not a true macrolide because the L-cladinose moiety at position C3 has been replaced by a keto group and by alkylaryl side chains at positions C11, C12.
Sites of interaction of streptogramin A and B antibiotics in the peptidyl transferase loop of 23S rRNA and the synergism of their inhibitory mechanisms.