Department of Physiology and Biophysics, MetroHealth, Cleveland, OH 44109, USA.
Structure. 2012 Jan 11;20(1):41-55. doi: 10.1016/j.str.2011.11.013.
The sterile alpha motif (SAM) for protein-protein interactions is encountered in over 200 proteins, but the structural basis for its interactions is just becoming clear. Here we solved the structure of the EphA2-SHIP2 SAM:SAM heterodimeric complex by use of NMR restraints from chemical shift perturbations, NOE and RDC experiments. Specific contacts between the protein surfaces differ significantly from a previous model and other SAM:SAM complexes. Molecular dynamics and docking simulations indicate fluctuations in the complex toward alternate, higher energy conformations. The interface suggests that EphA family members bind to SHIP2 SAM, whereas EphB members may not; correspondingly, we demonstrate binding of EphA1, but not of EphB2, to SHIP2. A variant of EphB2 SAM was designed that binds SHIP2. Functional characterization of a mutant EphA2 compromised in SHIP2 binding reveals two previously unrecognized functions of SHIP2 in suppressing ligand-induced activation of EphA2 and in promoting receptor coordinated chemotactic cell migration.
蛋白-蛋白相互作用的无菌α基序（SAM）存在于 200 多种蛋白质中，但它的相互作用结构基础才刚刚开始显现。在这里，我们通过使用来自化学位移扰动、NOE 和 RDC 实验的 NMR 约束，解决了 EphA2-SHIP2 SAM：SAM 异源二聚体复合物的结构。蛋白质表面之间的特定接触与之前的模型和其他 SAM：SAM 复合物有很大的不同。分子动力学和对接模拟表明，复合物会向替代的、能量更高的构象发生波动。该界面表明 EphA 家族成员与 SHIP2 SAM 结合，而 EphB 成员可能不会；相应地，我们证明 EphA1 与 SHIP2 结合，但 EphB2 不与 SHIP2 结合。设计了 EphB2 SAM 的变体，它与 SHIP2 结合。对 EphA2 中结合 SHIP2 能力受损的突变体的功能表征揭示了 SHIP2 在抑制配体诱导的 EphA2 激活和促进受体协调的趋化细胞迁移中的两个以前未被认识的功能。
