Fusidic acid-dependent ribosomal complexes protect Escherichia coli ribosomes from the action of the type 1 ribosome-inactivating protein crotin 2.

The type 1 ribosome-inactivating protein crotin 2 depurinated Escherichia coli ribosomes which, upon treatment of the isolated rRNA with acid aniline, released a fragment of around 240 nucleotides whose 5'-end sequence was 5'-GAGGACCGGAGUGGAC-3'. The formation of fusidic acid-dependent ribosomal complexes completely prevented release of the fragment. Ribosomes from crotin 2-pretreated fusidic acid complexes were insensitive to acid aniline. They released the RNA fragment only after a second treatment with crotin 2 and acid aniline whereas unprotected ribosomes released the fragment directly after acid aniline.