The Hedgehog pathway is an essential cell‐signaling paradigm implicated in cancer tumorigenesis and the developmental disorder holoprosencephaly, making it an attractive target for therapeutic design. The N‐terminal domain of the Sonic Hedgehog protein (Shh‐N) is the essential signaling molecule in the Hedgehog pathway. In this role Shh‐N interacts with its cognate membrane receptor Patched, as well as the regulatory proteins HHIP and CDO, by utilizing interfaces harboring one or more divalent ions. Here, the crystal structure of human Shh‐N is presented at 1.43 Å resolution, representing a landmark in the characterization of this protein. The structure reveals that the conserved Zn²⁺‐binding site adopts an atypical octahedral coordination geometry, whereas an adjacent binding site, normally occupied by binuclear Ca²⁺, has been supplanted by a single octahedrally bound Mg²⁺. Both divalent sites are compared with those in previous Shh‐N structures, which demonstrates a significant degree of plasticity of the Shh‐N protein in terms of divalent ion binding. The presence of a high Mg²⁺ concentration in the crystallization medium appears to have influenced metal loading at both metal ion‐binding sites. These observations have technical and design implications for efforts focused on the development of inhibitors that target Shh‐N‐mediated protein–protein interactions.

中文翻译：

---

Sonic Hedgehog 蛋白与锌 (II) 和镁 (II) 复合物的结构揭示了与肽药物设计相关的离子配位可塑性。


Hedgehog 通路是一种重要的细胞信号传导范式，与癌症肿瘤发生和发育障碍前脑无裂畸形有关，使其成为治疗设计的一个有吸引力的目标。 Sonic Hedgehog 蛋白 (Shh-N) 的 N 末端结构域是 Hedgehog 通路中的重要信号分子。在这一角色中，Shh-N 通过利用含有一个或多个二价离子的界面与其同源膜受体 Patched 以及调节蛋白 HHIP 和 CDO 相互作用。在这里，人类 Shh-N 的晶体结构以 1.43 Å 的分辨率呈现，代表了该蛋白质表征的一个里程碑。该结构表明，保守的 Zn ²⁺结合位点采用非典型的八面体配位几何形状，而通常由双核 Ca ²⁺占据的相邻结合位点已被单个八面体结合的 Mg ²⁺取代。将两个二价位点与之前的Shh-N结构中的位点进行比较，这表明Shh-N蛋白在二价离子结合方面具有显着程度的可塑性。结晶介质中存在高浓度 Mg ²⁺似乎影响了两个金属离子结合位点的金属负载量。这些观察结果对于专注于开发针对 Shh-N 介导的蛋白质-蛋白质相互作用的抑制剂的努力具有技术和设计意义。