Taylor Jonathan D, Ababou Abdessamad, Fawaz Radwan R, Hobbs Christopher J, Williams Mark A, Ladbury John E
Department of Biochemistry and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, UK.
Proteins. 2008 Dec;73(4):929-40. doi: 10.1002/prot.22119.
SH2 domains provide fundamental recognition sites in tyrosine kinase-mediated signaling pathways which, when aberrant, give rise to disease states such as cancer, diabetes, and immune deficiency. Designing specific inhibitors that target the SH2 domain-binding site, however, have presented a major challenge. Despite well over a decade of intensive research, clinically useful SH2 domain inhibitors have yet to become available. A better understanding of the structural, dynamic, and thermodynamic contributions to ligand binding of individual SH2 domains will provide some insight as to whether inhibitor development is possible. We report the first high resolution solution structure of the apo-v-Src SH2 domain. This is accompanied by the analysis of backbone dynamics and pK(a) values within the apo- and peptide-bound states. Our results indicate that the phosphotyrosine (pY) pocket is tightly structured and hence not adaptable to exogenous ligands. On the other hand, the pocket which accommodates residues proximal and C-terminal of the pY (pY + 3) or so-called specificity determining region, is a large dynamic-binding surface. This appears to allow a high level of promiscuity in binding. Binding of a series of synthetic, phosphotyrosyl, peptidomimetic compounds designed to explore interactions in the pY + 3 pocket further demonstrates the ability of the SH2 domain to accommodate diverse ligands. The thermodynamic parameters of these interactions show dramatic enthalpy/entropy compensation. These data suggest that the v-Src SH2 domain does not have a highly specific secondary-binding site, which clearly presents a major hurdle to design selective inhibitors.
SH2结构域在酪氨酸激酶介导的信号通路中提供基本的识别位点，这些位点异常时会引发癌症、糖尿病和免疫缺陷等疾病状态。然而，设计靶向SH2结构域结合位点的特异性抑制剂一直是一项重大挑战。尽管经过了十多年的深入研究，但临床上有用的SH2结构域抑制剂仍未问世。更好地理解单个SH2结构域对配体结合的结构、动力学和热力学贡献，将有助于了解抑制剂开发是否可行。我们报道了无配体v-Src SH2结构域的首个高分辨率溶液结构。同时还分析了无配体状态和肽结合状态下的主链动力学和pK(a)值。我们的结果表明，磷酸酪氨酸（pY）口袋结构紧密，因此不适合结合外源性配体。另一方面，容纳pY近端和C末端残基（pY + 3）或所谓特异性决定区域的口袋是一个大的动态结合表面。这似乎允许在结合中具有高度的混杂性。一系列旨在进一步探索pY + 3口袋中相互作用的合成磷酸酪氨酸肽模拟化合物的结合，进一步证明了SH2结构域容纳多种配体的能力。这些相互作用的热力学参数显示出显著的焓/熵补偿。这些数据表明，v-Src SH2结构域没有高度特异性的二级结合位点，这显然是设计选择性抑制剂的一个主要障碍。
