[3H]anisomycin binding to eukaryotic ribosomes

Abstract

Anisomycin, a well-known inhibitor of eukaryotic ribosomes' peptidyl-transferase activity, specifically binds to the 60 S ribosome subunit. Quantitative studies on [3H]anisomycin binding to yeast and human tonsil ribosomes have shown that a maximum of one molecule of the antibiotic is bound per ribosome in both cases. There is a single type of binding to 60 S subunits but ribosomes themselves are not homogeneous with respect to [3H]anisomycin binding, since the interaction between antibiotic and ribosome occurs with two different affinities. Only ribosomes having the higher type of affinity for [3H]anisomycin are active in catalysing peptide bond formation, as tested in both the puromycin and the fragment reaction assays. Affinity of [3H]anisomycin for ribosomes is higher at 0 °C than at 30 °C. Affinity is decreased in the presence of ethanol. The acetate group in the 3′ position of the pyrrolidine ring of anisomycin is important for the anisomycin-ribosome interaction since deacetylanisomycin appears to have a mode of action similar to anisomycin but has an affinity for the ribosome that is 350 times smaller. The effect of certain peptidyl-transferase inhibitors has been tested on [3H]anisomycin binding to ribosomes. Using either yeast or human tonsil ribosomes a number of sesquiterpene antibiotics of the trichodermin group (trichodermin, trichodennol, fusarenon X and trichothecin) totally block [3H]anisomycin binding whereas puromycin and verrucarin A only partially inhibit the [3H]anisomycin interaction with ribosomes. Gougerotin, blasticidin S and actinobolin have no effect. Tenuazonic acid and sparsomycin inhibit [3H]anisomycin binding to ribosomes but the degree of inhibition differs between yeast and human tonsil ribosomes. © 1974.