Reduced-denatured ribonuclease A is not in a compact state.
Dynamic light scattering and circular dichroism experiments were performed to determine the compactness and residual secondary structure of reduced and by 6 M guanidine hydrochloride denatured ribonuclease A. We find that reduction of the four disulphide bonds by dithiothreitol at 20 degrees C leads to total unfolding and that a temperature increase has no further effect on the dimension. The Stokes' radius of ribonuclease A at 20 degrees C is R(s) = (1.90 +/- 0.04) nm (native) and R(s) = (3.14 +/- 0.06) nm (reduced-denatured). Furthermore, circular dichroism spectra do not indicate any residual secondary structure. We suggest that reduced-denatured Ribonuclease A has a random coil-like conformation and is not in a compact denatured state.
Nöppert
A
A
Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
Gast
K
K
Müller-Frohne
M
M
Zirwer
D
D
Damaschun
G
G
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D004229:Dithiothreitol / Q000494:pharmacology; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology; D008027:Light; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012259:Ribonuclease, Pancreatic / Q000737:chemistry*; D012542:Scattering, Radiation
D006146:Guanidines; D012259:Ribonuclease, Pancreatic; D019791:Guanidine; D004229:Dithiothreitol