Effect of different mutations in ribosomal protein S5 of Escherichia coli on translational fidelity.

The effect of three different types of mutations in ribosomal protein S5 of Escherichia coli on translational fidelity has been studied. Two of them, namely that conferring resistance to spectinomycin and that selected for partial suppression of a temperature-sensitive analyl-tRNA synthetase mutation, do not exhibit ribosomal ambiguity in the in vivo and in vitro test system employed. In contrast, mutations in ribosomal protein S5 selected for suppression of streptomycin dependence mutations are able to derestrict the restriction of translational ambiguity imposed by str A mutations, though to different degrees depending on the type of mutation. Mutants in which streptomycin dependence is suppressed by an alteration in protein S5 are more restrictive than mutants resistant to streptomycin. Again, the extent of restriction depends on the type of the str Ad allele. mutations in ribosomal protein S5 can act as ram mutations like mutations in protein S4. The part of the S5 polypeptide involved in control of translational fidelity is different from regions altered in spectinomycin resistant strains and in the alanyl-tRNA synthetase suppressor mutant.