Increasing the potency of a cytotoxin with an arginine graft

Protein Eng Des Sel. 2007 Oct;20(10):505-9. doi: 10.1093/protein/gzm051. Epub 2007 Oct 22.


Variants and homologs of bovine pancreatic ribonuclease (RNase A) can exhibit cytotoxic activity. This toxicity relies on cellular internalization of the enzyme. Residues Glu49 and Asp53 form an anionic patch on the surface of RNase A. We find that replacing these two residues with arginine does not affect catalytic activity or affinity for the cytosolic ribonuclease inhibitor (RI) protein. This 'arginine graft' does, however, increase toxicity towards human cancer cells. Appending a nonaarginine domain to this cationic variant results in an additional increase in cytotoxicity, providing one of the most cytotoxic known variants of RNase A. These findings correlate the potency of a ribonuclease with its deliverance of ribonucleolytic activity to the cytosol, and indicate a rational means to enhance the efficacy of ribonucleases and other cytotoxic proteins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Amino Acids, Acidic / chemistry
  • Animals
  • Arginine / genetics
  • Arginine / metabolism*
  • Binding Sites
  • Cations / chemistry
  • Cattle
  • Cell Line
  • Cytotoxins / chemistry*
  • Cytotoxins / genetics
  • Cytotoxins / metabolism
  • Cytotoxins / toxicity*
  • Databases, Protein
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Kinetics
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Permeability
  • Protein Structure, Quaternary
  • Proteins / chemistry
  • Recombinant Proteins
  • Ribonuclease, Pancreatic / antagonists & inhibitors
  • Ribonuclease, Pancreatic / chemistry*
  • Ribonuclease, Pancreatic / genetics
  • Ribonuclease, Pancreatic / metabolism*


  • Amino Acids, Acidic
  • Cations
  • Cytotoxins
  • Intracellular Signaling Peptides and Proteins
  • Proteins
  • Recombinant Proteins
  • ribonuclease inhibitor, porcine
  • Arginine
  • Ribonuclease, Pancreatic