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The mode of action of Shiga toxin on peptide elongation of eukaryotic protein synthesis.

ABSTRACT: The effect of Shiga toxin, from Shigella dysenteriae 1, on the component reactions of peptide elongation were investigated. Enzymic binding of [3H]phenylalanine-tRNA to reticulocyte ribosomes was inhibited by 50% at 7 nM toxin. Elongation factor 1 (eEF-1)-dependent GTPase activity was also inhibited. Both reactions were not restored by addition of excess eEF-1 protein. In contrast, toxin concentrations of 200 nM were required to inhibit by 50% the elongation factor 2 (eEF-2)-dependent translocation of aminoacyl-tRNA on ribosomes. Addition of excess eEF-2 restored translocation activity. The eEF-2-dependent GTPase activity was unaffected at toxin concentrations below 100 nM, and Shiga-toxin concentrations of up to 1,000 nM did not affect either GTP.eEF-2.ribosome complex-formation or peptidyltransferase activity. Thus Shiga toxin closely resembles alpha-sarcin in action, both being primary inhibitors of eEF-1-dependent reactions. In contrast, the 60 S ribosome inactivators ricin and phytolaccin are primary inhibitors of eEF-2-dependent reactions of peptide elongation.

SUBMITTER: Obrig TG

PROVIDER: S-EPMC1147989 | biostudies-other | 1987 Jun

REPOSITORIES: biostudies-other

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