Action Mechanism of Mikamycins. III Further Studies on the Site of Action of Mikamycins

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It has been shown by detailed studies of several workers that such antibiotics as chloramphenicol^1,2), tetracycline¹³⁾, puromycin³⁾ and streptomycin⁴⁾ inhibit protein synthesis and that the site of action of these antibiotics are in transfer of amino acid from soluble RNA to protein in the pathway of protein synthesis. In the previous paper⁵⁾, mikamycins were reported to inhibit the incorporation of ¹⁴C-leucine into protein without effect on the incorporation into RNA. From the result, it was suggested that the actual site of action of mikamycins might be also located in the step of transfer of amino acid from soluble RNA to protein.

In the present study, to investigate this problem, the soluble and ribosomal fraction were separated from the cells of Staphylococcus aureus and Micrococcus lysodeikticus after the incubation with ¹⁴C-amino acid mixture or >¹⁴C-leucine in the presence or absence of mikamycins. From both fractions the RNA and protein fractions were prepared and the incorporation of amino acid into these fractions were studied. Effect of mikamycins on the synthesis of RNA and protein was comparably studied.