Evenäs J, Tugarinov V, Skrynnikov N R, Goto N K, Muhandiram R, Kay L E
Protein Engineering Network Centres of Excellence, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
J Mol Biol. 2001 Jun 15;309(4):961-74. doi: 10.1006/jmbi.2001.4695.
Solution NMR studies on the physiologically relevant ligand-free and maltotriose-bound states of maltodextrin-binding protein (MBP) are presented. Together with existing data on MBP in complex with beta-cyclodextrin (non-physiological, inactive ligand), these new results provide valuable information on changes in local structure, dynamics and global fold that occur upon ligand binding to this two-domain protein. By measuring a large number of different one-bond residual dipolar couplings, the domain conformations, critical for biological function, were investigated for all three states of MBP. Structural models of the solution conformation of MBP in a number of different forms were generated from the experimental dipolar coupling data and X-ray crystal structures using a quasi-rigid-body domain orientation algorithm implemented in the structure calculation program CNS. Excellent agreement between relative domain orientations in ligand-free and maltotriose-bound solution conformations and the corresponding crystal structures is observed. These results are in contrast to those obtained for the MBP/beta-cyclodextrin complex where the solution state is found to be approximately 10 degrees more closed than the crystalline state. The present study highlights the utility of residual dipolar couplings for orienting protein domains or macromolecules with respect to each other.
本文介绍了对麦芽糖糊精结合蛋白（MBP）的生理相关无配体状态和麦芽三糖结合状态进行的溶液核磁共振研究。结合现有的MBP与β-环糊精（非生理、无活性配体）复合物的数据，这些新结果提供了关于配体结合到这种双结构域蛋白时局部结构、动力学和整体折叠变化的有价值信息。通过测量大量不同的一键残余偶极耦合，研究了MBP所有三种状态下对生物功能至关重要的结构域构象。使用结构计算程序CNS中实现的准刚体结构域取向算法，从实验偶极耦合数据和X射线晶体结构生成了多种不同形式的MBP溶液构象的结构模型。在无配体和麦芽三糖结合的溶液构象中的相对结构域取向与相应的晶体结构之间观察到了极好的一致性。这些结果与MBP/β-环糊精复合物的结果形成对比，在该复合物中，溶液状态比晶体状态大约封闭10度。本研究突出了残余偶极耦合在确定蛋白质结构域或大分子彼此之间取向方面的效用。
