Irreversible Inactivation of Ribosomes by Antibiotics

Summary

The peptide bond-forming activity (as measured by the puromycin reaction) of ribosomes (E. coli) charged with poly (U) and Ac-phe-tRNA at the P-site, is abolished irreversibly by spiramycin (10⁻⁵M). The rate of this inactivation is decreased by chloramphenicol (3 × 10⁻⁶M) or lincomycin (10⁻⁵M) but it is not affected by gougerotin (9 × 10⁻⁵M). In contrast to spiramycin, sparsomycin (10⁻⁷M) decreases irreversibly the activity of the ribosomal complex but does not abolish it. On the assumption that the antibiotics remain bound to the modified ribosome, these results may mean that, in contrast to previous proposals, sparsomycin and puromycin do not bind to overlapping sites whereas spiramycin and puromycin may bind to overlapping sites.