Denatured states of ribonuclease A have compact dimensions and residual secondary structure.
Using small-angle X-ray scattering and Fourier transform infrared spectroscopy, we have determined that the thermally denatured state of native ribonuclease A is on average a compact structure having residual secondary structure. Under strongly reducing conditions, the protein further unfolds into a looser structure with larger dimensions but still retains a comparable amount of secondary structure. The dimensions of the thermally and chemically denatured states of the reduced protein are different but both are more compact than is predicted for a random coil of the same length. These results demonstrate that thermal denaturation in ribonuclease A is not a simple two-state transition from a native to a completely disordered random coil state.
Sosnick
T R
TR
Life Sciences Division, Los Alamos National Laboratory, New Mexico 87545.
Trewhella
J
J
D000818:Animals; D002417:Cattle; D005583:Fourier Analysis; D007700:Kinetics; D011487:Protein Conformation; D011489:Protein Denaturation; D012259:Ribonuclease, Pancreatic / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics; D014961:X-Ray Diffraction
D012259:Ribonuclease, Pancreatic