Puromycin

Puromycin enters the vacant A site without the involvement of EF-Tu. It is a substrate for peptidyl transferase through its amino group forming peptidyl puromycin. Peptidyl puromycin is not anchored to the A site, and dissociates from the ribosome, resulting in premature chain termination. About 50% of ribosomes react with puromycin – those with vacant A sites.