Streptothricin F, an inhibitor of protein synthesis with miscoding activity.

The effect of streptothricin F on macromolecular syntheses in intact cells and cell-free protein synthesis of E. coli was studied. The results indicate that protein synthesis is the primary site of inhibition by streptothricin F in growing E. coli cells. Cell-free polypeptide synthesis from E. coli directed by poly (U) was inhibited, while poly (A) and poly (C) directed polypeptide syntheses were both stimulated by the drug. Furthermore, streptothricin F caused misreading of translation of poly (U), poly (A) and poly (C) directed protein syntheses in E. coli systems. The extent of misreading by streptothricin F increases with increasing drug concentrations. The results are compared with those of other miscoding antibiotics. In rat liver extracts protein directed by poly (U) or endogenous mRNA was not inhibited.