Stimulation by Aminoglycosidic Antibiotics of DNA-directed Protein Synthesis

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Abstract
The incorporation of 14C-amino acid into protein by DNA was markedly increased by the presence of kanamycin and neomycin in a cell-free system from E. coli. Less stimulation was observed with streptomycin. Kasugamycin did not significantly affect the amino acid incorporation by DNA. 3H-Thymidine-labeled heat-denatured E. coli DNA was found to attach to the ribosomes by sucrose density gradient centrifugation and neomycin did not affect the attachment of DNA to the ribosomes. The binding of sRNA labeled with 14C-phenylalanine, 14C-serine, or 14C-amino acids mixture to DNA-ribosome complex was investigated by the sucrose density gradient centrifugation and the Millipore filter method. Kanamycin, neomycin, or streptomycin was observed to stimulate the binding of aminoacyl-sRNA, whereas kasugamycin did not significantly affect the binding. Kasugamycin inhibited neomycin-stimu-lated binding of aminoacyl-sRNA to the ribosomes with DNA. The grade of stimulation of the binding was less than but parallel to that of the amino acid incorporation. The stimulation by neomycin of the amino acid incorporation and the binding of aminoacyl-sRNA to the ribosomes with DNA were much reduced, when the ribosomes were obtained from neomycin-resistant E. coli. However, they were significantly enhanced by kanamycin or streptomycin. The significance of the antibiotic-stimulated binding of aminoacyl-sRNA to the ribosomes for the antibiotic-stimulated, DNA-directed protein synthesis is discussed.

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