Visualization of transient encounter complexes in protein-protein association
Visualization of transient encounter complexes in protein-protein association
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DOI：
10.1038/nature05201
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发表时间：
2006-11-16
期刊：
影响因子：
64.8
通讯作者：
Clore, G. Marius
中科院分区：
文献类型：
--
作者：
Tang, Chun;Iwahara, Junji;Clore, G. Marius
关于许多蛋白质-蛋白质缔合的动力学数据已经为初始形成的预平衡遭遇复合物（pre-equilibrium encounter complex）提供了证据，该复合物随后松弛为最终的立体特异性复合物（1）。定点诱变（2 - 4）和布朗动力学模拟（5 - 7）已经表明，缔合速率可以通过直接相互作用表面外部的电荷分布的扰动来调节。此外，通过非特异性结合的速率增强可以通过维数的降低（8）或短程、非特异性吸引势的存在（9）来发生。在这里，使用顺磁弛豫增强，我们直接证明了存在和可视化的一个合奏的瞬态，非特异性的遭遇复合物的平衡条件下，一个相对较弱的蛋白质-蛋白质复合物之间的氨基末端结构域的酶I和磷酸化载体蛋白HPr的分布。无论是单独的立体特异性复合物（10）还是任何单一的替代构象都不能完全解释分子间顺磁弛豫增强数据。对顺磁弛豫增强数据的约束刚体模拟退火细化使我们能够获得非特异性相遇复合物系综的原子概率分布图，该系综与相互作用蛋白质上的静电表面势定性相关。对于另外两种蛋白质-蛋白质复合物也给出了类似的定性结果。
Kinetic data on a number of protein - protein associations have provided evidence for the initial formation of a pre- equilibrium encounter complex that subsequently relaxes to the final stereospecific complex (1). Site- directed mutagenesis(2 - 4) and brownian dynamics simulations(5 - 7) have suggested that the rate of association can be modulated by perturbations in charge distribution outside the direct interaction surfaces. Furthermore, rate enhancement through non- specific binding may occur by either a reduction in dimensionality(8) or the presence of a short- range, non- specific attractive potential(9). Here, using paramagnetic relaxation enhancement, we directly demonstrate the existence and visualize the distribution of an ensemble of transient, non- specific encounter complexes under equilibrium conditions for a relatively weak protein - protein complex between the amino- terminal domain of enzyme I and the phosphocarrier protein HPr. Neither the stereospecific complex(10) alone nor any single alternative conformation can account fully for the intermolecular paramagnetic relaxation enhancement data. Restrained rigid- body simulated annealing refinement against the paramagnetic relaxation enhancement data enables us to obtain an atomic probability distribution map of the non- specific encounter complex ensemble that qualitatively correlates with the electrostatic surface potentials on the interacting proteins. Qualitatively similar results are presented for two other protein - protein complexes.