Structural Characterization of the EphA4-Ephrin-B2 Complex Reveals New Features Enabling Eph-Ephrin Binding Promiscuity
Structural Characterization of the EphA4-Ephrin-B2 Complex Reveals New Features Enabling Eph-Ephrin Binding Promiscuity
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DOI：
10.1074/jbc.m109.064824
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发表时间：
2010-01-01
影响因子：
4.8
通讯作者：
Song, Jianxing
中科院分区：
文献类型：
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作者：
Qin, Haina;Noberini, Roberta;Song, Jianxing
EphA和EphB受体分别优先结合肝配蛋白A和肝配蛋白B配体，但EphA 4结合所有肝配蛋白的能力是例外的。在这里，我们报告的晶体结构的EphA 4配体结合域与肝配蛋白-B2，这代表了第一个结构的EphA-ephrin-B类间复合物的复合物。EphA 4配体结合通道中肝配蛋白-B2 G-H环的松散配合与相对弱的结合亲和力一致。EphA 4残基Gln（12）和Glu（14）与肝配蛋白-B2之间也存在额外的表面接触。Gln（12）和Glu（14）的突变不引起EphA 4的显著结构变化或其对肝配蛋白-A配体的亲和力的变化。然而，EphA 4突变体对肝配蛋白-B配体的亲和力降低了近10倍，表明表面接触对于类间而非类内肝配蛋白结合至关重要。因此，EphA 4使用不同的策略来结合肝配蛋白-A或肝配蛋白-B配体并实现结合混杂。NMR表征还表明Gln（12）和Glu（14）与肝配蛋白-B2的接触在整个EphA 4配体结合结构域中诱导动态变化。我们的研究结果揭示了EphA 4的显著配体结合混杂性的独特特征，并表明需要多种策略来有效地破坏不同的Eph-ephrin复合物。
EphA and EphB receptors preferentially bind ephrin-A and ephrin-B ligands, respectively, but EphA4 is exceptional for its ability to bind all ephrins. Here, we report the crystal structure of the EphA4 ligand-binding domain in complex with ephrin-B2, which represents the first structure of an EphA-ephrin-B interclass complex. A loose fit of the ephrin-B2 G-H loop in the EphA4 ligand-binding channel is consistent with a relatively weak binding affinity. Additional surface contacts also exist between EphA4 residues Gln(12) and Glu(14) and ephrin-B2. Mutation of Gln(12) and Glu(14) does not cause significant structural changes in EphA4 or changes in its affinity for ephrin-A ligands. However, the EphA4 mutant has similar to 10-fold reduced affinity for ephrin-B ligands, indicating that the surface contacts are critical for interclass but not intraclass ephrin binding. Thus, EphA4 uses different strategies to bind ephrin-A or ephrin-B ligands and achieve binding promiscuity. NMR characterization also suggests that the contacts of Gln(12) and Glu(14) with ephrin-B2 induce dynamic changes throughout the whole EphA4 ligand-binding domain. Our findings shed light on the distinctive features that enable the remarkable ligand binding promiscuity of EphA4 and suggest that diverse strategies are needed to effectively disrupt different Eph-ephrin complexes.