Unfolding intermediate of a multidomain protein, calmodulin, in urea as revealed by small‐angle X‐ray scattering

FEBS Letters

Yoshino, Hidenori²  Matsufuji, Tomohiro¹  Jinbo, Yuji¹  Izumi, Yoshinobu¹  Yokouchi, Tsuyoshi¹ 

[1] Graduate Program of Human Sensing and Functional Sensor Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jo-nan, Yonezawa 992-8510, Japan;Department of Chemistry, Sapporo Medical University, S-1, W-17, Chuo-ku, Sapporo 060-0061, Japan

关键词: Calmodulin;    Calcium binding;    Peptide binding;    Urea denaturation;    Small-angle X-ray scattering;    Unfolding intermediate;   

DOI  :  10.1016/S0014-5793(03)00907-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The denaturation of calmodulin (CaM) induced by urea has been studied by small-angle X-ray scattering, which is a direct way to evaluate the shape changes in a protein molecule. In the absence of Ca²⁺, the radii of gyration (R _g) of CaM are 20.8±0.3 Å in the native state and about 34±1.0 Å in the unfolded state. The transition curve derived from Kratky plots indicates a bimodal transition via a stable unfolding intermediate around 2.5 M urea. In the presence of Ca²⁺ and in the presence of both Ca²⁺ and a target peptide, the R _g values are 21.5±0.3 and 18.1±0.3 Å in the native state and 26.7±0.4 and 24.9±0.4 Å at 9 M urea, respectively. The results indicate that a stable unfolding intermediate still persists in 9 M urea. The present results suggest that the shape of unfolding intermediates is an asymmetric dumbbell-like structure, one in the folded and one in the unfolded state.

【 授权许可】

Unknown