Since no ribosomal protein has been found to be responsible for tetracycline binding to the ribosome, and no ribosomal protein mutants conferring tetracycline resistance to ribosomes have been detected, it is strongly believed that the antibiotic specifically interacts with a structural element of 16S ribosomal RNA. According to the results of foot-printing experiments (Noller et al., 1990), tetracycline protects A892 located in the side loop of the hairpin occupying position at the interdomain junction of the 16S RNA (see Fig. 6.1). The same base is specifically protected also by the A-site-bound tRNA (but not P-site-bound tRNA). Among ribosomal proteins, protein S7 seems to be the nearest neighbour of the tetracycline-binding site.

Figure 10.9. Streptomycin.

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