Streptomycin Resistance and Ribosomal Proteins: Amino Acid Substitutions in the str Protein of One Streptomycin-Resistant Mutant of Escherichia coli K12 after Mutagenesis with Ethyl Methanesulfonate
One streptomycin-resistant mutant of Escherichia coli K12 was selected after treatment with ethyl methanesulfonate. Comparison of tryptic peptide maps was used to investigate chemical changes in the str protein, S12. Two changes could be detected, which, from the comparison of the total amino acid composition, appear to result from the replacement of one tyrosine by one phenylalanine residue, and of one valine by one alanine residue. The observed amino acid substitutions differ from those found in protein S12 of previously investigated streptomycin-resistant mutants.