Glassy dynamics of protein methyl groups revealed by deuteron NMR.
Glassy dynamics of protein methyl groups revealed by deuteron NMR.
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氘核核磁共振揭示蛋白质甲基的玻璃态动力学。
DOI：
10.1021/jp311112j
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Vold,RobertL
中科院分区：
文献类型：
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作者：
Vugmeyster,Liliya;Ostrovsky,Dmitry;Penland,Kirsten;Hoatson,GinaL;Vold,RobertL
我们研究了在298和140 K之间的温度范围内，使用氘固态核磁共振纵向弛豫测量的鸡绒毛头部亚结构域（HP 36）的疏水核心中的关键甲基基团的位点特异性动力学。纵向磁化强度的弛豫在高温下是弱非指数（玻璃态）的，并且在低于约175 K时表现出更强的非指数性。此外，特征弛豫时间偏离简单的阿克里乌斯定律。我们解释这种行为通过存在的三个站点的甲基跳跃，这源于有点不同的甲基环境内的本地能源景观的活化能势垒的分布。甲基跃迁的活化能垒的分布宽度相当大，约为1.4 kJ/mol。我们的实验结果和建模允许在约175 K的表观变化的描述，而不调用一个特定的转变温度。对于核心中的大多数残基来说，高温下的弛豫行为表明景观亚态之间存在构象交换，我们的模型考虑了这一过程的动力学。观察到的动力学是相同的干燥和水合蛋白质。我们还研究了疏水核心内的F58 L突变对其中一个残基的动力学的影响，并观察到在高温下其构象交换速率常数显着增加。
We investigated site-specific dynamics of key methyl groups in the hydrophobic core of chicken villin headpiece subdomain (HP36) over the temperature range between 298 and 140 K using deuteron solid-state NMR longitudinal relaxation measurements. The relaxation of the longitudinal magnetization is weakly nonexponential (glassy) at high temperatures and exhibits a stronger degree of nonexponentiality below about 175 K. In addition, the characteristic relaxation times deviate from the simple Arrhenius law. We interpret this behavior via the existence of distribution of activation energy barriers for the three-site methyl jumps, which originates from somewhat different methyl environments within the local energy landscape. The width of the distribution of the activation barriers for methyl jumps is rather significant, about 1.4 kJ/mol. Our experimental results and modeling allow for the description of the apparent change at about 175 K without invoking a specific transition temperature. For most residues in the core, the relaxation behavior at high temperatures points to the existence of conformational exchange between the substates of the landscape, and our model takes into account the kinetics of this process. The observed dynamics are the same for dry and hydrated protein. We also looked at the effect of F58L mutation inside the hydrophobic core on the dynamics of one of the residues and observed a significant increase in its conformational exchange rate constant at high temperatures.