The compactness of ribonuclease A and reduced ribonuclease A.
The compactness of ribonuclease A with intact disulfide bonds and reduced ribonuclease A was investigated by synchrotron small-angle X-ray scattering. The Rg values and the Kratky plots showed that non-reduced ribonuclease A maintain a compact shape with a Rg value of about 17.3 A in 8 M urea. The reduced ribonuclease A is more expanded, its Rg value is about 20 A in 50 mM Tris-HCl buffer at pH 8.1 containing 20 mM DTT. Further expansions of reduced ribonuclease A were observed in the presence of high concentrations of denaturants, indicating that reduced ribonuclease A is more expanded and is in neither a random coil [A. Noppert et al., FEBS Lett. 380 (1996) 179-182] nor a compact denatured state [T.R. Sosnick and J. Trewhella, Biochemistry 31 (1992) 8329-8335]. The four disulfide bonds keep ribonuclease A in a compact state in the presence of high concentrations of urea.
National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Beijing, PR China. zhoujm@sun5.ibp.ac.cn
J M
JM
Zhou
Y X
YX
Fan
H
H
Kihara
K
K
Kimura
Y
Y
Amemiya
D000818:Animals; D002417:Cattle; D004220:Disulfides / Q000737:chemistry*; D010084:Oxidation-Reduction; D011489:Protein Denaturation; D012259:Ribonuclease, Pancreatic / Q000737:chemistry*; D012542:Scattering, Radiation; D017356:Synchrotrons; D014508:Urea
D004220:Disulfides; D014508:Urea; D012259:Ribonuclease, Pancreatic