Genetic code and streptomycin: Their relation to ribosomal subunits

Abstract

The following combinations of synthetic polynucleotide and aminoacyl-sRNA caused binding of the aminoacyl-sRNA to the 30-S ribosomal subunits in the absence of 50-S ribosomal subunits: leucyl-sRNA (poly (U 8, A, C), poly (U 8, G, C), poly (U 4, G), poly (U 4, A), poly (U)), seryl-sRNA (poly (U 8, A, C), poly (U 8, G, C)), isoleucyl-sRNA (poly (U 4, A), poly (U 8, A, C), valyl-sRNA (poly (U 4, G), poly (U 8, G, C)), tyrosyl-sRNA (poly (U 8, A, C)), lysyl-sRNA (poly (A 3, G)). Streptomycin does not stimulate the binding of isoleucyl-sRNA to 30-S subunit-template complex, while it stimulates the binding of isoleucyl-sRNA to ribosome-template complex. When ribosomes were dissociated into their subunits and the subunits were reassociated by raising the concentration of Mg 2+, streptomycin did not stimulate the binding of isoleucyl-sRNA to these reassociated ribosomes in the presence of poly (U), poly (U 4, A), or poly (U 8, A, C). The incorporation of [ 14C]isoleucine into hot trichloroacetic acid-insoluble material in the presence of these synthetic polynucleotides and 2·10 −2 M Mg 2+ by the reassociated ribosomes was greater than that by the non-treated ribosomes. Streptomycin did not influence the incorporation of isoleucine into polypeptide by reassociated ribosomes under the direction of poly (U 4, A), while it stimulated the incorporation by non-treated ribosomes under the same conditions.