title: Non-specific depurination activity of saporin-S6, a ribosome-inactivating protein, under acidic conditions.
abstract: Among five ribosome-inactivating proteins tested only saporin-S6 could efficiently release the adenine from adenosine 20 of the synthetic oligoribonucleotide (SRD RNA) mimic of the sarcin/ricin domain of rat 28S rRNA with a Km of 9 microM and a kcat of approximately 0.4 min(-1) at pH 7.6. The optimal pH for the depurination activity of saporin-S6 is 5.0. However, saporin-S6 lost its site-specificity of depurination on SRD RNA around the optimal pH. The non-specific depurination activity of saporin-S6 was dependent on the enzyme concentration and pH conditions. These results are valuable to understand the diversity and the depurination mechanism of ribosome-inactivating proteins.
authors.affiliation: Shanghai Institute of Biochemistry, Academia Sinica, China.
authors.forename: S
authors.initials: S
authors.lastname: Tang
authors.forename: R G
authors.initials: RG
authors.lastname: Hu
authors.forename: W Y
authors.initials: WY
authors.lastname: Liu
authors.forename: K C
authors.initials: KC
authors.lastname: Ruan
mesh_terms: D000225:Adenine / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D003851:Deoxyribonucleases / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004587:Electrophoresis, Agar Gel; D006863:Hydrogen-Ion Concentration; D000922:Immunotoxins; D007700:Kinetics; D018716:Molecular Mimicry; D009699:N-Glycosyl Hydrolases; D009843:Oligoribonucleotides / Q000737:chemistry / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D012339:RNA, Ribosomal, 28S / Q000737:chemistry; D051381:Rats; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins; D013379:Substrate Specificity
chemical_list: D000922:Immunotoxins; D009843:Oligoribonucleotides; D010940:Plant Proteins; D012339:RNA, Ribosomal, 28S; D054789:Ribosome Inactivating Proteins, Type 1; D003851:Deoxyribonucleases; D009699:N-Glycosyl Hydrolases; D000076985:Saporins; D000225:Adenine