Zhou J M, Fan Y X, Kihara H, Kimura K, Amemiya Y
National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Beijing, PR China.
FEBS Lett. 1998 Jul 3;430(3):275-7. doi: 10.1016/s0014-5793(98)00639-5.
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.
通过同步辐射小角X射线散射研究了具有完整二硫键的核糖核酸酶A和还原型核糖核酸酶A的紧密程度。Rg值和Kratky图表明，在8 M尿素中，未还原的核糖核酸酶A保持紧密形状，Rg值约为17.3 Å。还原型核糖核酸酶A更为伸展，在含有20 mM二硫苏糖醇（DTT）、pH 8.1的50 mM Tris-HCl缓冲液中，其Rg值约为20 Å。在高浓度变性剂存在下，观察到还原型核糖核酸酶A进一步伸展，这表明还原型核糖核酸酶A更为伸展，既不是无规卷曲状态[A. Noppert等人，《欧洲生物化学学会联合会快报》380 (1996) 179 - 182]，也不是紧密变性状态[T.R. Sosnick和J. Trewhella，《生物化学》31 (1992) 8329 - 8335]。在高浓度尿素存在下，四个二硫键使核糖核酸酶A保持紧密状态。
