The mechanism of action of barley toxin: a type 1 ribosome-inactivating protein with RNA N-glycosidase activity.
In a previous report (Endo, Y. and Tsurugi, K. (1987) J. Biol. Chem. 262, 8128-8130) it was shown that the RNA N-glycosidase activity of ricin A-chain was responsible for the ability of this protein to inactivate eukaryotic ribosomes. The objective of the present study was to determine whether a similar mechanism was used by a ribosome-inactivating protein from pearled barley (barley toxin). Rat liver ribosomes were incubated either with ricin A-chain or barley toxin, and the rRNA was extracted and treated with acidic aniline to hydrolyze phosphodiester bonds rendered susceptible by removal of a purine or pyrimidine base. Evaluation of the rRNA by polyacrylamide/agarose electrophoresis disclosed two 28 S rRNA-derived fragments which differed in size from those generated by untreated (control) ribosomes. Sequencing of the smaller of these fragments confirmed that - as is the case for ricin A-chain - the aniline-sensitive site in barley toxin-treated ribosomes was between A and G in 28 S rRNA. We conclude that barley toxin inactivates ribosomes via a mechanism identical to that of ricin A-chain: enzymatic hydrolysis of the N-glycosidic bond at A of 28 S rRNA.
Endo
Y
Y
Department of Biochemistry, Yamanashi Medical College, Japan.
Tsurugi
K
K
Ebert
R F
RF
D000818:Animals; D001467:Hordeum; D008099:Liver / Q000378:metabolism; D008970:Molecular Weight; D009699:N-Glycosyl Hydrolases / Q000302:isolation & purification* / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism*; D012339:RNA, Ribosomal, 28S / Q000378:metabolism*; D051381:Rats; D054788:Ribosome Inactivating Proteins; D012270:Ribosomes / Q000187:drug effects* / Q000378:metabolism; D014118:Toxins, Biological / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology
D012335:RNA, Ribosomal; D012339:RNA, Ribosomal, 28S; D014118:Toxins, Biological; D009699:N-Glycosyl Hydrolases; D054788:Ribosome Inactivating Proteins