Antibiotic action of puromycin. Puromycin resembles the aminoacyl terminus of an aminoacyl-tRNA. Its amino group joins the carboxyl group of the growing polypeptide chain to form peptidyl-puromycin that dissociates from the ribosome. Peptidyl-puromycin is stable because puromycin has an amide (shown in red) rather than an ester linkage.