title: Shiga toxin, Shiga-like toxin II variant, and ricin are all single-site RNA N-glycosidases of 28 S RNA when microinjected into Xenopus oocytes.
abstract: Ricin, Shiga toxin, and Shiga-like toxin II (SLT-II, Vero toxin 2) exhibit an RNA N-glycosidase activity which specifically removes a single base near the 3' end of 28 S rRNA in isolated rat liver ribosomes and deproteinized 28 S rRNA (Endo Y., Mitsui, K., Motizuki, M., & Tsurugi, K. (1987) J. Biol. Chem. 262, 5908-5912; Endo Y. & Tsurugi, K. (1987) J. Biol. Chem. 262, 8128-8130, Endo, Y., Tsurugi, K., Yutsudo, T., Takeda, Y., Ogasawara, K. & Igarashi, K. (1988) Eur. J. Biochem. 171, 45-50). These workers identified the single base removed, A-4324, by examining a 28 S rRNA degradation product which was generated by contaminating ribonucleases associated with the ribosomes. To determine whether this N-glycosidase activity applies in living cells, we microinjected ricin into Xenopus oocytes. We also microinjected Shiga toxin and a variant of Shiga-like toxin II (SLT-IIv). All three toxins specifically removed A-3732, located 378 nucleotides from the 3' end of 28 S rRNA. This base is analogous to the site observed in rat 28 S rRNA for ricin, Shiga toxin, and SLT-II. Purified, glycosylated, ricin A chain contains this RNA N-glycosidase activity in oocytes. We also demonstrated that the nonglycosylated A subunit of recombinant ricin exhibits this RNA N-glycosidase activity when injected into Xenopus oocytes. Ricin, Shiga toxin, and SLT-IIv also caused a rapid decline in oocyte protein synthesis for nonsecretory proteins.
authors.affiliation: Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
authors.forename: S K
authors.initials: SK
authors.lastname: Saxena
authors.forename: A D
authors.initials: AD
authors.lastname: O'Brien
authors.forename: E J
authors.initials: EJ
authors.lastname: Ackerman
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000008:administration & dosage / Q000378:metabolism*; D001483:Base Sequence; D003603:Cytotoxins / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology; D005260:Female; D008845:Microinjections; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism*; D012339:RNA, Ribosomal, 28S / Q000378:metabolism*; D054788:Ribosome Inactivating Proteins; D012276:Ricin / Q000008:administration & dosage / Q000378:metabolism*; D022641:Shiga Toxin 2; D022603:Shiga Toxins; D013379:Substrate Specificity; D014981:Xenopus
chemical_list: D001427:Bacterial Toxins; D003603:Cytotoxins; D012335:RNA, Ribosomal; D012339:RNA, Ribosomal, 28S; D022641:Shiga Toxin 2; D022603:Shiga Toxins; D012276:Ricin; D009699:N-Glycosyl Hydrolases; D054788:Ribosome Inactivating Proteins