Tolman J R, Al-Hashimi H M, Kay L E, Prestegard J H
Protein Engineering Network Centers of Excellence, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
J Am Chem Soc. 2001 Feb 21;123(7):1416-24. doi: 10.1021/ja002500y.
The measurement of residual dipolar couplings in weakly aligned proteins can potentially provide unique information on their structure and dynamics in the solution state. The challenge is to extract the information of interest from the measurements, which normally reflect a convolution of the structural and dynamic properties. We discuss here a formalism which allows a first order separation of their effects, and thus, a simultaneous extraction of structural and motional parameters from residual dipolar coupling data. We introduce some terminology, namely a generalized degree of order, which is necessary for a meaningful discussion of the effects of motion on residual dipolar coupling measurements. We also illustrate this new methodology using an extensive set of residual dipolar coupling measurements made on (15)N,(13)C-labeled human ubiquitin solvated in a dilute bicelle solution. Our results support a solution structure of ubiquitin which on average agrees well with the X-ray structure (Vijay-Kumar, et al., J. Mol. Biol. 1987, 194, 531--544) for the protein core. However, the data are also consistent with a dynamic model of ubiquitin, exhibiting variable amplitudes, and anisotropy, of internal motions. This work suggests the possibility of primary use of residual dipolar couplings in characterizing both structure and anisotropic internal motions of proteins in the solution state.
测量弱对齐蛋白质中的剩余偶极耦合有可能提供有关其溶液状态下结构和动力学的独特信息。挑战在于从测量中提取感兴趣的信息，这些测量通常反映了结构和动力学性质的卷积。我们在此讨论一种形式主义，它允许对它们的效应进行一阶分离，从而从剩余偶极耦合数据中同时提取结构和运动参数。我们引入一些术语，即广义有序度，这对于有意义地讨论运动对剩余偶极耦合测量的影响是必要的。我们还使用在稀释双分子层溶液中溶剂化的（15）N，（13）C标记的人泛素上进行的大量剩余偶极耦合测量来说明这种新方法。我们的结果支持泛素的溶液结构，其平均与蛋白质核心的X射线结构（Vijay-Kumar等人，《分子生物学杂志》，1987年，194卷，531 - 544页）非常吻合。然而，数据也与泛素的动态模型一致，该模型表现出内部运动的可变幅度和各向异性。这项工作表明了在表征溶液状态下蛋白质的结构和各向异性内部运动时主要使用剩余偶极耦合的可能性。
