Studies on the Action of Tetracycline and Puromycin

By means of a convenient method for separating phenylalanyl puromycin from diphenylalanyl puromycin, it was found that, upon reaction with puromycin, phenylalanyl transfer RNA bound to ribosomes at 5 to 6 mm Mg++ yields phenylalanyl puromycin exclusively while phenylalanyltRNA bound at 13 mm Mg++ yields diphenylalanyl puromycin as well as phenylalanyl puromycin. Tetracycline inhibited mostly the binding of phenylalanyl-tRNA to the acceptor site, but the binding to the donor site may be inhibited at 13 mm Mg++. Puromycin reaction of phenylalanyl-tRNA bound to the donor site was inhibited by the presence of N-acetylphenylalanyl-tRNA at the acceptor site.