Farrow N A, Zhang O, Forman-Kay J D, Kay L E
Protein Engineering Network Centres of Excellence, Department of Medical Genetics, University of Toronto, Ontario, Canada.
Biochemistry. 1997 Mar 4;36(9):2390-402. doi: 10.1021/bi962548h.
Measurements of 15N NMR relaxation parameters have been used to characterize the backbone dynamics of folded and denatured states of the N-terminal SH3 domain from the adapter protein drk, in high salt or guanidinium chloride, respectively. Values of the spectral density function evaluated at a number of frequencies are compared. The levels of backbone dynamics in the folded protein show little variation across the molecule and are of similar magnitude to those determined previously for the folded state of the protein in exchange with an unfolded state at low salt concentrations [Farrow et al. (1995) Biochemistry 34, 868-878]. The denatured state of the domain exhibits both more extensive and more heterogeneous dynamics than the folded state. In particular the profile of the spectral density function evaluated at zero-frequency for the unfolded state of the domain indicates that residues in the middle of the protein sequence are considerably less mobile than those at the termini. These data suggest that the molecule is not behaving as an extended polymer and that concerted motions of the central portions of the molecule are occurring, consistent with a reasonably compact conformation in this region. The backbone dynamics of the folded and unfolded states were studied at two temperatures. The level of high-frequency motions in the folded molecule is largely unaffected by changes in temperature, whereas an increase in temperature results in increased high-frequency motion in the unfolded state.
分别在高盐或氯化胍条件下，利用15N核磁共振弛豫参数测量来表征衔接蛋白drk的N端SH3结构域折叠态和变性态的主链动力学。比较了在多个频率下评估的光谱密度函数值。折叠蛋白中主链动力学水平在整个分子中变化不大，其幅度与先前在低盐浓度下蛋白质折叠态与未折叠态交换时测定的幅度相似[Farrow等人（1995年），《生物化学》34卷，868 - 878页]。该结构域的变性态比折叠态表现出更广泛和更不均匀的动力学。特别是，在该结构域未折叠态零频率下评估的光谱密度函数曲线表明，蛋白质序列中部的残基比末端的残基移动性明显更低。这些数据表明，该分子的行为不像伸展的聚合物，并且分子中部存在协同运动，这与该区域合理紧凑的构象一致。在两个温度下研究了折叠态和未折叠态的主链动力学。折叠分子中高频运动的水平在很大程度上不受温度变化的影响，而温度升高会导致未折叠态中高频运动增加。
