The use of residual dipolar coupling in concert with backbone relaxation rates to identify conformational exchange by NMR
The use of residual dipolar coupling in concert with backbone relaxation rates to identify conformational exchange by NMR
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DOI：
10.1021/ja990062t
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发表时间：
1999-05-05
影响因子：
15
通讯作者：
Tjandra, N
中科院分区：
文献类型：
--
作者：
de Alba, E;Baber, JL;Tjandra, N
在液晶存在下，大分子的轻微排列可以测量偶极耦合，否则这些偶极耦合将被分子的快速旋转扩散平均掉。偶极耦合提供了重要和独特的结构信息。1虽然排列的机制尚不清楚，但已有研究表明，中性脂形成的液晶双细胞2，3通过与大分子的空间相互作用而诱导排列。4这种机理只能依赖于大分子的形状。由于分子形状也控制着转动扩散，我们认为取向和转动扩散张量可能具有相似的取向。这两个张量在任何其他方面都不具有可比性，也就是说，它们的大小通常是不相关的。对于非各向同性扩散体，T1/T2比与键矢相对于扩散张量主轴系统的取向有关。5通过检查Lee等人建议的局部扩散常数的表达式，6很明显，该参数和偶极耦合相对于它们各自张量中的键方向的依赖是相似的。因此，如果我们关于取向和扩散张量之间的相似性的假设被证明是正确的，那么T1/T2比和偶极耦合之间的良好相关性是可望的。在本文报告的工作中，发现了这两个参数之间的显著相关性。此外，还表明这种相关性可以用于识别骨架发生构象交换的残基。用三种蛋白质，人泛素、hnRNP K的C-末端结构域(Kh3)和人G-α相互作用蛋白(GAIP)的实验数据说明了该方法的适用性。异核驰豫数据已被用来揭示内部动力学，7-10和表征大分子的各向异性旋转扩散参数。6、11、12当旋转扩散各向异性有利时，异核T1/T2比甚至可以提供重要的结构信息
The slight alignment of a macromolecule in the presence of liquid crystal allows the measurement of dipolar couplings which otherwise would be averaged out by fast rotational diffusion of the molecule. Dipolar couplings provide important and unique structural information. 1 Although the mechanism of alignment is still not clear, it has been suggested that the liquid crystal bicelles2, 3 formed by neutral lipids induce alignment through steric interactions with the macromolecules. 4 This type of mechanism can only be dependent on the shape of the macromolecule. Since the molecular shape also governs the rotational diffusion, we suggest that the alignment and the rotational diffusion tensors may have similar orientations. The two tensors would not be comparable in any other way, that is, their magnitudes in general would be uncorrelated. For nonisotropic diffusors T1/T2 ratios are related to the orientation of the bond vector with respect to the principal axis system of the diffusion tensor. 5 By examining the expression of the local diffusion constants suggested by Lee et al., 6 it becomes apparent that the dependence of this parameter and the dipolar coupling with respect to bond orientation in their respective tensors is similar. Therefore, should our hypothesis concerning the similarity between the orientations of the alignment and diffusion tensors prove true, a good correlation between T1/T2 ratios and dipolar couplings is expected. In the work reported herein a respectable correlation between these two parameters is found. Furthermore, it is also shown that this correlation can be used to identify residues whose backbones undergo conformational exchange. The applicability of this approach is illustrated using experimental data for three proteins, human ubiquitin, C-terminal domain of hnRNP K (KH3), and human G-alpha interacting protein (GAIP).Heteronuclear relaxation data has been used to reveal internal dynamics, 7-10 and to characterize the anisotropic rotational diffusion parameters of macromolecules. 6, 11, 12 When the rotational diffusion anisotropy is favorable, the heteronuclear T1/T2 ratios can even provide important structural information in the form of