Non-specific depurination activity of saporin-S6, a ribosome-inactivating protein, under acidic conditions

Biol Chem. 2000 Aug;381(8):769-72. doi: 10.1515/BC.2000.098.

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / metabolism*
  • Animals
  • Binding Sites
  • Deoxyribonucleases / chemistry
  • Deoxyribonucleases / metabolism
  • Dose-Response Relationship, Drug
  • Electrophoresis, Agar Gel
  • Hydrogen-Ion Concentration
  • Immunotoxins*
  • Kinetics
  • Molecular Mimicry
  • N-Glycosyl Hydrolases*
  • Oligoribonucleotides / chemistry
  • Oligoribonucleotides / metabolism
  • Plant Proteins / chemistry
  • Plant Proteins / metabolism*
  • RNA, Ribosomal, 28S / chemistry
  • Rats
  • Ribosome Inactivating Proteins, Type 1
  • Saporins
  • Substrate Specificity

Substances

  • Immunotoxins
  • Oligoribonucleotides
  • Plant Proteins
  • RNA, Ribosomal, 28S
  • Ribosome Inactivating Proteins, Type 1
  • Deoxyribonucleases
  • N-Glycosyl Hydrolases
  • Saporins
  • Adenine