Effects of emetine on the specific association of T-2 toxin with mammalian cells.

The effects of emetine on the association of T-2 toxin with Chinese hamster ovary cells were examined. T-2 toxin-cell association at both 4 degrees C and 37 degrees C was reduced by up to 90% after preincubation of cells with emetine. Emetine-induced reduction in T-2 toxin-cell association was time-, temperature-, and concentration-dependent. A 4-min preincubation with emetine at physiological temperature was required to develop the maximum inhibitory effect. After brief exposures (< or = 5 min), emetine's inhibitory effects on toxin-cell association were reversible. However, after longer exposure periods to emetine (60 min), toxin-cell association was irreversibly blocked. The addition of emetine to cells prebound with toxin resulted in dissociation at a rate 2 to 3 times slower than a competitive chase with nonlabeled toxin. Emetine did not compete directly for T-2 toxin binding to its receptor on isolated, purified, run-off ribosomes. However, the binding of toxin to purified ribosomes prepared from cells preincubated with emetine was markedly reduced. Scatchard analysis indicated that emetine's inhibitory effects on T-2 toxin-cell association were mediated through mixed allosteric and competitive types of inhibition at specific, intracellular, T-2 toxin ribosomal binding sites.