The cytotoxins alpha-sarcin and ricin retain their specificity when tested on a synthetic oligoribonucleotide (35-mer) that mimics a region of 28 S ribosomal ribonucleic acid.
An oligoribonucleotide (35-mer) that mimics the alpha-sarcin and the ricin region of eukaryotic 28 S rRNA was transcribed in vitro from a synthetic template with T7 RNA polymerase and was used to test whether the specificity of the hydrolysis by the toxins was retained. alpha-Sarcin, at a low concentration, cleaved a single phosphodiester bond on the 3' side of a guanosine residue in the synthetic oligomer that corresponds to G-4325 in 28 S rRNA, the site of action of the toxin in intact ribosomes. At a high concentration of alpha-sarcin, the substrate (35-mer) was hydrolyzed after each of its purines. alpha-Sarcin was without an effect on a synthetic RNA (20-mer) that reproduces the near universal sequence of nucleotides in the loop, but lacks the stem, of the toxin's domain. Thus, the specificity of the attack of alpha-sarcin on a precise region of 28 S rRNA appears to be contingent on the sequence of the nucleotides and the structure of the domain. Ricin depurinated a nucleotide in the synthetic oligomer (35-mer), and in the presence of aniline the phosphoribose backbone was cleaved at a position that conforms to A-4324 in 28 S rRNA, the site of action of the toxin in vivo.
Endo
Y
Y
Department of Biochemistry, Yamanashi Medical School, Japan.
Chan
Y L
YL
Lin
A
A
Tsurugi
K
K
Wool
I G
IG
D001483:Base Sequence; D001665:Binding Sites; D004722:Endoribonucleases; D005656:Fungal Proteins / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D009843:Oligoribonucleotides / Q000138:chemical synthesis / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism*; D012339:RNA, Ribosomal, 28S / Q000378:metabolism*; D012276:Ricin / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D005656:Fungal Proteins; D009843:Oligoribonucleotides; D012335:RNA, Ribosomal; D012339:RNA, Ribosomal, 28S; C014801:alpha-sarcin; D012276:Ricin; D004722:Endoribonucleases