@article {SMITHERS433, author = {DONALD SMITHERS and L. LEE BENNETT, JR. and ROBERT F. STRUCK}, title = {Inhibition of Protein Synthesis in Mammalian Cells by Actinobolin}, volume = {5}, number = {5}, pages = {433--445}, year = {1969}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {Actinobolin, an antibiotic with a broad spectrum of biological activity, has been studied with respect to its metabolic effects in mammalian cells. In mouse Adenocarcinoma 755 cells, both in vivo and in cell culture, actinobolin inhibited the synthesis of protein and DNA, but exerted a much smaller effect on the synthesis of RNA and had no effect on the synthesis of soluble purine derivatives. The rate and extent of uptake of [3H]actinobolin in cell cultures suggested passive diffusion across the cell membrane, with no subsequent covalent bonding to cellular constituents. In a cell-free system, containing washed ribosomes and 100,000 x g-pH 5 fractions from mouse Adenocarcinoma 755 cells grown in culture, actinobolin inhibited the incorporation of labeled amino acids in the presence of endogenous messenger or of polyuridylate. At higher concentrations actinobolin inhibited the incorporation of thymidylate into DNA in a crude DNA synthetase system. These results suggest that the primary metabolic effect of actinobolin in mammalian cells is on protein synthesis. In the cell-free system actinobolin (a) did not inhibit the formation of aminoacyl-tRNAs, (b) did not cause the release of peptides from previously charged ribosomes or prevent such release by puromycin, and (c) inhibited the binding of [14C]phenylalanyl-tRNA to the poly U-ribosome complex, but not the binding of poly U to ribosomes. These results show that actinobolin acts at a late stage of protein synthesis, perhaps by competing with aminoacyl-tRNAs. Such an action would be compatible with the fact that actinobolin contains an L-alanine moiety. ACKNOWLEDGMENTS We are indebted to Miss D. Adamson, Mrs. M. H. Vail, and Miss F. Chesnutt for provision of cell cultures, and to Mr. T. C. Herren and Mr. H. Finch for assays of radioisotopes.}, issn = {0026-895X}, URL = {https://molpharm.aspetjournals.org/content/5/5/433}, eprint = {https://molpharm.aspetjournals.org/content/5/5/433.full.pdf}, journal = {Molecular Pharmacology} }