Mechanisms in protein synthesis XII. sites of action of showdomycin in a cell-free polyphenylalanine synthesizing system from human lymphatic tissue: Ribosomes and elongation factor TF II

Abstract

Inhibition of polyphenylalanine synthesis by showdomycin was found in a human cell-free system. Preincubation of elongation factor TF II with showdomycin, and subsequent removal of excess antibiotic resulted in almost complete inactivation of the factor, as assayed in polyphenylalanine synthesis. Ribosomes treated and tested in the same way were only partially (∼50%) inactivated. TF I and ribosomal peptidyl transferase were virtually not affected by showdomycin. Further experiments showed that this antibiotic inhibits non-enzymatic and enzymatic phenylalanyl-tRNA binding to ribosomes, besides its effects on translocation.