Localization of Sensitivity to Kanamycin and Streptomycin in 30s Ribosomal Proteins of Escherichia Coli

The localization in ribosomes of sensitivity to kanamycin was investigated and compared with that to streptomycin, using ribosomes from a mutant of Escherichia coli resistant to both these antibiotics. It was demonstrated that the sensitivity to both antibiotics was located in the 30S subunit. The 30S subunit was fractionated into a 23S core and split proteins 30, and the 23S core was split further into core proteins 30 and 16S ribosomal RNA. It was found that the sensitivity to kanamycin as well as to streptomycin resided in proteins of the 23S core. To identify the responsible component, 30S ribosomal proteins from the parent strain and from a kanamycin-resistant mutant were labelled differently, and co-chromatographed through carboxymethylcellulose column. Only one component (P10) was observed to appear inconsistently in the elution profile, and it was therefore assumed to be the component that determined the sensitivity to kanamycin. This assumption was confirmed by examining the inhibition by kanamycin in poly U-directed incorporation of phenylalanine with 30S subunits reconstituted in different combinations between P10 and the other components from the two origins. This component and the component controlling sensitivity to streptomycin were identical. It was observed that the reconstituted ribosomes containing P10 from either resistant mutant were resistant to both antibiotics, and P10 protein in both mutants was altered.