Effect of dihydrostreptomycin on protein synthesis in whole cells and in cell-free extracts of a streptomycin-dependent strain of Escherichia coli B.

The effect of dihydrostreptomycin on the incorporation of amino acids into protein in antibiotic-deprived cells of a streptomycin-dependent strain of Escherichia coli B has been compared with its effect on protein synthesis in extracts from cells of the same strain. Stimulation of phenylalanine incorporation into protein in whole cells occurred within 5 min of addition of dihydrostreptomycin to a deprived culture and was maximal at an antibiotic concentration of 20 mug/ml. Stimulation of protein synthesis in cell-free extracts from antibiotic-deprived cells was maximal at a dihydrostreptomycin concentration of 10 mug/ml in systems programmed with f2-ribonucleic acid and poly AGU, whereas extracts from cells grown on nonlimiting concentrations of dihydrostreptomycin were unaffected by the addition of antibiotic. These results indicate that protein synthesis is an antibiotic-requiring process in streptomycin-dependent E. coli B.