Multiple effects of kanamycin on translational accuracy

We have studied the effects of kanamycin on the accuracy of translation in vitro by wild-type and mutant ribosomes from Escherichia coli. Kanamycin stimulates the leucine missense error of poly(U) translation by wild-type, Ram, and streptomycin-resistant ribosomes in characteristic ways; in particular, the streptomycin-resistant ribosomes are significantly less error-prone than wild-type or Ram ribosomes at all concentrations of the antibiotic. Kinetic analysis of the effects of kanamycin on the translational accuracy of wild-type ribosomes reveals a different concentration dependence for the perturbation of the initial selectivity and for the proofreading. Furthermore, the initial selectivity of streptomycin-resistant ribosomes is not affected by kanamycin; the drug enhances only the error of proofreading by this mutant ribosome. We suggest that the multiple effects of kanamycin on the errors of translation are due to separate effects at different ribosomal sites.