Inhibition of protein synthesis in reticulocyte lysates by trichodermin

Abstract

The effect of trichodermin as an inhibitor of eukaryotic protein synthesis was studied in a [rabbit] reticulocyte cell-free system. Trichodermin at a concentration of 25 .mu.g/ml inhibits total protein synthesis instantaneously and stabilizes polyribosome profiles. At a concentration of 0.25 .mu.g/ml the drug inhibits total protein synthesis by only 70-75% and allows 30-35% breakdown of the polyribosomes in the system. These effects were compared with those produced by 2 other drugs (pactamycin and anisomycin) examined under conditions identical with those used for trichodermin. At high concentration (25 .mu.g/ml) trichodermin inhibits elongation at the level of the peptidyl transferase catalytic center. At low concentration (0.25 .mu.g/ml) trichodermin inhibits peptide-bond formation at the initiation stage and inhibits elongation only secondarily, although at the lower concentration both inhibitory effects are incomplete. The results presented exclude any possibility that, under the conditions used here in vitro, trichodermin can act preferentially as an inhibitor of the termination step in protein synthesis.