Studies on the Mode of Action of Pactamycin

Abstract

Pactamycin inhibits the synthesis of protein in microorganisms and in mammalian cells. The mode of action was studied in Bacillus subtilis. Pactamycin in low doses stimulates the synthesis of RNA. The amount of sRNA in the treated cells can increase up to threefold, the amount of ribosomal RNA up to twofold, when compared with the corresponding controls. In ribosomal fractions, isolated from pactamycin treated B. subtilis, the relative concentration of 100S particles is markedly decreased depending on the dose and time of incubation. The 70S ribosomes loose their property to form the 100S dimer. These ribosomal fractions are much less active in cell free synthesis of polyphenylalanine than the corresponding controls. The acceptor activity of tRNA was not affected when enzyme fractions from pactamycin treated B. subtilis were used. Pactamycin interferes with the synthesis of protein at the ribosomal level. Probably the antibiotic differs in its mode of action from chloramphenicol and puromycin.