Crystal structural analysis of protein-protein interactions drastically destabilized by a single mutation
Crystal structural analysis of protein-protein interactions drastically destabilized by a single mutation
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DOI：
10.1110/ps.073322508
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发表时间：
2008-06-01
期刊：
影响因子：
8
通讯作者：
Ito, Nobutoshi
中科院分区：
文献类型：
--
作者：
Urakubo, Yoshiaki;Ikura, Teikichi;Ito, Nobutoshi
Barnase(Bn)和barstar(Bs)的复合体被广泛研究为蛋白质-蛋白质相互作用的定量分析模型，但单个突变(bs Asp39->；Ala)显著破坏了该复合体的稳定性，对应于结合自由能变化7.7kcal.mol(-1)。然而，目前还没有结构性信息来解释这种严重的不稳定。在本研究中，我们通过X射线结晶学确定了1.58埃分辨率的突变络合物的结构。该复合体在整体结构和界面结构上与野生型复合体相似，但界面处水分子介导的氢键网络明显不同。几个水分子填满了由突变造成的空腔，从而导致界面上的水合水分子重新排列。水分子被重新分布成通道状的结构，该结构穿透到复合体中。此外，分子动力学模拟表明，该突变增加了水分子在界面上的流动性。由于在bN和bs的其他突变复合体中没有观察到水化作用的如此剧烈的变化，相互作用的显著不稳定可能是由于水合水分子的这种通道状结构。
The complex of barnase (bn) and barstar (bs), which has been widely studied as a model for quantitative analysis of protein-protein interactions, is significantly destabilized by a single mutation, namely, bs Asp39 -> Ala, which corresponds to a change of 7.7 kcal.mol(-1) in the free energy of binding. However, there has been no structural information available to explain such a drastic destabilization. In the present study, we determined the structure of the mutant complex at 1.58 angstrom resolution by X-ray crystallography. The complex was similar to the wild-type complex in terms of overall and interface structures; however, the hydrogen bond network mediated by water molecules at the interface was significantly different. Several water molecules filled the cavity created by the mutation and consequently caused rearrangement of the hydrated water molecules at the interface. The water molecules were redistributed into a channel-like structure that penetrated into the complex. Furthermore, molecular dynamics simulations showed that the mutation increased the mobility of water molecules at the interface. Since such a drastic change in hydration was not observed in other mutant complexes of bn and bs, the significant destabilization of the interaction may be due to this channel-like structure of hydrated water molecules.