Cooperative control of translational fidelity by ribosomal proteins in Escherichia coli. II. Localization of amino acid replacements in proteins S5 and S12 altered in double mutants resistant to neamine.

Protein S5 and S12 were isolated from 30S ribosomal subunits of two E. coli mutants highly resistant to the antibiotic neamine, and of the parental strain. Proteinchemical analyses on these proteins led to the following results: a) In protein S5 the arginine residue in peptide T2 of the parental strain is replaced by glycine in one (nea 314) or serine in the other (nea 319) of the two mutants. b) In protein S12 The proline residue in peptide T15 of the parental strain is replaced by leucine in mutant nea 314 and by glutamine in mutant nea 319. Comparison of these results with those obtained in earlier studies on other mutants with altered ribosomal proteins revealed that the amino acid replacements in neamine resistant mutants and in "revertants" from streptomycin dependence occur at the same amino acid positions of proteins S5 and S12. Therefore it is likely that both types of mutants belong to the same class.