Inhibition of Protein Biosynthesis in Escherichia coli B by Tri‐l‐ornithine

Triornithine completely inhibited growth of Escherichia coli B in the minimal liquid medium M63. The di‐, tetra‐ and pentapeptides showed no effect on the growth of the bacterium. Triornithine, when added to a bacterial culture, inhibited the incorporation of ¹⁴C‐labeled amino acids into the protein fraction, but did not suppress the incorporation of [³H]uridine and [³H]thymidine. The tripeptide inhibited translation of the induced β‐galactosidase mRNA and also inhibited the synthesis of alkaline phosphatase initiated by derepression. Triornithine had no effect on the reaction in vitro of T4‐DNA‐directed RNA synthesis. Incubation of E. coli B cells with triornithine impaired the protein biosynthetic system of the treated cells in vitro. By this treatment the biological activity of the ribosomal fraction is impaired within the bacterial cell. Triornithine, even at a high concentration, did not inhibit in vitro the polypeptide synthesis in a cell‐free system.