Microscopic origins of entropy, heat capacity and the glass transition in proteins
Microscopic origins of entropy, heat capacity and the glass transition in proteins
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DOI：
10.1038/35078119
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发表时间：
2001-05-24
期刊：
影响因子：
64.8
通讯作者：
Wand, AJ
中科院分区：
文献类型：
--
作者：
Lee, AL;Wand, AJ
内部运动对于蛋白质折叠 (1)、通过产生的残余熵实现蛋白质稳定性 (2) 以及蛋白质功能 (1,3-7) 至关重要。尽管蛋白质大分子的内部运动很重要，但其精确性质仍然是个谜。在这里，我们报告了使用位点特异性氘核磁共振弛豫方法对钙调蛋白-肽复合物中含甲基侧链的快速动力学的温度依赖性的调查。运动幅度具有明显的异质谱，并分为三个截然不同的类别。在单一温度下研究的其他蛋白质往往会发生类似的分离。此外，钙调蛋白复合物中动力学热激活程度的巨大变化表明残余熵的异质分布，从而揭示了蛋白质热容量的微观起源。这些观察结果还为蛋白质的低温“玻璃化转变”提供了意想不到的解释。正是这种转变归因于负责生物活性的蛋白质运动模式的创建(5-7)。
Internal motion is central to protein folding(1), to protein stability through the resulting residual entropy(2), and to protein function(1,3-7). Despite its importance, the precise nature of the internal motions of protein macromolecules remains a mystery. Here we report a survey of the temperature dependence of the fast dynamics of methyl-bearing side chains in a calmodulin-peptide complex using site-specific deuterium NMR relaxation methods. The amplitudes of motion had a markedly heterogeneous spectrum and segregated into three largely distinct classes. Other proteins studied at single temperatures tend to segregate similarly. Furthermore, a large variability in the degree of thermal activation of the dynamics in the calmodulin complex indicates a heterogeneous distribution of residual entropy and hence reveals the microscopic origins of heat capacity in proteins. These observations also point to an unexpected explanation for the low-temperature 'glass transition' of proteins. It is this transition that has been ascribed to the creation of protein motional modes that are responsible for biological activity(5-7).