Backbone dynamics of the natively unfolded pro-peptide of subtilisin by heteronuclear NMR relaxation studies
Backbone dynamics of the natively unfolded pro-peptide of subtilisin by heteronuclear NMR relaxation studies
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DOI：
10.1023/a:1011243116136
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发表时间：
2001-07-01
影响因子：
2.7
通讯作者：
Baum, J
中科院分区：
文献类型：
--
作者：
Buevich, AV;Shinde, UP;Baum, J
用N-15松弛实验研究了枯草杆菌菌素前体肽(PPS)在两种不同pH值(6.0和3.0)下自然展开的动力学特征。获得了不同场强下的N-15驰豫数据，并对谱密度映射、无模型方法和最近提出的Cole-Cole无模型(CC-MF)分析进行了详细的比较。与传统的无模型方法相比，CC-MF分析对未折叠PPS的N-15驰豫数据的磁场依赖性提供了更好的拟合，并表明R-2的起伏可以由关联时间在纳秒时间尺度上的分布来解释。从分析中得到一个新的参数epsilon，它代表了分布函数的宽度和特定位置纳秒时间尺度上动力学的不均匀。特别有趣的是，观察到epsilon对pH变化很敏感，PPS在酸性较弱的PHS上采样的纳秒时间尺度运动比在酸性较强的PHS上的分布更广。这些结果表明，在pH为6.0时，PPS经历了较高程度的关联运动，静电相互作用可能是在未折叠的PPS中诱导纳秒时间尺度上的关联运动的重要因素。
The dynamics of the natively unfolded form of the pro-peptide of subtilisin (PPS) have been characterized at two different pHs (6.0 and 3.0) by N-15 relaxation experiments. N-15 relaxation data is obtained at multiple field strengths and a detailed comparison of spectral density mapping, the model free approach and the recently proposed Cole-Cole model free (CC-MF) analysis is presented. The CC-MF analysis provides a better fit to the observed magnetic field dependence of N-15 relaxation data of unfolded PPS than conventional model free approaches and shows that fluctuations in R-2 may be accounted for by a distribution of correlation times on the nanosecond timescale. A new parameter epsilon derives from the analysis and represents the width of the distribution function and the heterogeneity of the dynamics on the nanosecond timescale at a particular site. Particularly interesting is the observation that epsilon is sensitive to pH changes and that PPS samples a wider distribution of nanosecond time scale motions at less acidic pHs than at more acidic pHs. These results suggest that PPS experiences a higher degree of correlated motion at pH 6.0 and that electrostatic interactions may be important for inducing correlated motions on the nanosecond timescale in unfolded PPS.