Three-state thermal unfolding of onconase

Biophys Chem. 2011 Dec;159(2-3):267-74. doi: 10.1016/j.bpc.2011.07.005. Epub 2011 Jul 24.


Onconase is a member of the ribonuclease A superfamily currently in phase IIIb clinical trials as a treatment for malign mesothelioma due to its cytotoxic activity selective against tumor-cells. In this work, we have studied the equilibrium thermal unfolding of onconase using a combination of several structural and biophysical techniques. Our results indicate that at least one significantly populated intermediate, which implies the exposure of hydrophobic surface and significant changes in the environment around Trp3, occurs during the equilibrium unfolding process of this protein. The intermediate begins to populate at about 30° below the global unfolding temperature, reaching a maximum population of nearly 60%, 10° below the global unfolding temperature.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amphibian Proteins / chemistry*
  • Animals
  • Antineoplastic Agents / chemistry*
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Unfolding*
  • Rana pipiens / metabolism*
  • Ribonucleases / chemistry*
  • Temperature


  • Amphibian Proteins
  • Antineoplastic Agents
  • Ribonucleases
  • ranpirnase