A streptomycin-resistant Escherichia coli mutant with ribosomes temperature-sensitive in the suppression of a nonsense codon

Cell free extracts from a streptomycin-resistant E. coli mutant which is also temperature-sensitive for Qβ phage were studied for suppression of a nonsense mutation at various temperatures. The streptomycin-resistant ribosomes of the mutant were found to be temperature-sensitive in suppression of an amber mutation in f2 phage coat protein while retaining the ability to synthesize proteins at an elevated temperature (42° C). The restriction of amber suppression at 42° C is assumed to be related to an alteration in the ribosomal protein S12 of the streptomycin-resistant mutant which also causes a change in its electrophoretic mobility.