Severity of the streptomycin resistance and streptomycin dependence phenotypes of ribosomal protein S12 of Thermus thermophilus depends on the identity of highly conserved amino acid residues

The structural basis for the streptomycin dependence phenotype of ribosomal protein S12 mutants is poorly understood. Here we describe the application of site-directed mutagenesis and gene replacement of Thermus thermophilus rpsL to assess the importance of side chain identity and tertiary interactions as phenotypic determinants of drug-dependent mutants.