Unfolding of dimeric creatine kinase in urea and guanidine hydrochloride as measured using small angle X‐ray scattering with synchrotron radiation

FEBS Letters

Fan, Ying-Xin³  Kimura, Kazumoto²  Zhou, Jun-Mei³  Kihara, Hiroshi⁴  Amemiya, Yoshiyuki¹ 

[1] Faculty of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan;Division of Medical Electronics, Dokkyo University School of Medicine, Mibu, Tochigi 321-02, Japan;National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Beijing 100101, China;Physics Laboratory, Kansai Medical University, Uyamahigashi, Hirakata, Osaka 573, Japan

关键词: Creatine kinase;    Protein unfolding;    Small angle X-ray scattering;    Dissociation;    Association;    SAXS;    small angle X-ray scattering;    CK;    creatine kinase;    GuHCl;    guanidine hydrochloride;    MG;    molten globule;   

DOI  :  10.1016/S0014-5793(97)01120-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The denaturation of dimeric creatine kinase (CK) induced by urea and guanidine hydrochloride (GuHCl) has been studied by small angle X-ray scattering (SAXS), which is a direct way to measure the changes in the overall dimensions of a protein molecule. The radii of gyration (R _g) of CK are 29±0.4 Å in the native state and 46±1.5 Å in the unfolded state in either 8 M urea or 3 M GuHCl. The transition curves of urea denaturation derived from the R _g values and the zero angle intensity (I(0)) are similar to that from intrinsic fluorescence, indicating that the changes in the molecular shape, the tertiary structure and the dissociation of the subunits proceed simultaneously. In the case of GuHCl-induced denaturation, the dramatic increases both in R _g and in I(0) in 0.3–0.5 M GuHCl suggest clearly that soluble aggregates form at low GuHCl concentrations. The aggregates dissociate and the molecule unfolds at higher GuHCl concentrations. The results suggest that the mechanisms of CK denaturation in urea and in GuHCl are somewhat different and the intermediate in GuHCl denaturation can much more easily form soluble aggregates.

【 授权许可】

Unknown