Effect of Tetracycline on Puromycin-Induced Polysome Degradation: Influence of Magnesium and Polyamines

Puromycin-induced polysome degradation has been shown to require G factor, guanosine 5'-triphosphate, and the presence of a ribosome release factor (Hirashima and Kaji, 1972, 1973). Tetracycline, which does not inhibit formation of peptidyl-puromycin (Gottesman, 1967; Sarkar and Thach, 1968) nor the guanosine 5'-triphosphate hydrolysis mediated by elongation factor Tu (Ono et al., 1969), inhibits polysome degradation. The tetracycline inhibition requires Mg(2+) at concentrations above 8 mM, which are inhibitory to protein synthesis in vitro. At concentrations of Mg(2+) below 8 mM, polysome degradation is insensitive to tetracycline, but not to fusidic acid. Addition of spermidine, but not of other polyamines, enables the tetracycline inhibition to occur at concentrations of Mg(2+) as low as 2 mM. The inhibition by tetracycline and by fusidic acid suggests that ribosome movement may be essential for the function of ribosome release factor, or that these antibiotics may directly affect its action.