Teneurins are ancient cell-cell adhesion receptors that are vital for brain development and synapse organisation. They originated in early metazoan evolution through a horizontal gene transfer event when a bacterial YD-repeat toxin fused to a eukaryotic receptor. We present X-ray crystallography and cryo-EM structures of two Teneurins, revealing a ~200 kDa extracellular super-fold in which eight sub-domains form an intricate structure centred on a spiralling YD-repeat shell. An alternatively spliced loop, which is implicated in homophilic Teneurin interaction and specificity, is exposed and thus poised for interaction. The N-terminal side of the shell is 'plugged' via a fibronectin-plug domain combination, which defines a new class of YD proteins. Unexpectedly, we find that these proteins are widespread amongst modern bacteria, suggesting early metazoan receptor evolution from a distinct class of proteins, which today includes both bacterial proteins and eukaryotic Teneurins.

中文翻译：

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Teneurin 粘附受体的结构揭示了细胞间相互作用的古老折叠。

Teneurins 是古老的细胞-细胞粘附受体，对大脑发育和突触组织至关重要。当细菌 YD 重复毒素与真核受体融合时，它们起源于通过水平基因转移事件的早期后生动物进化。我们展示了两个 Teneurin 的 X 射线晶体学和冷冻电镜结构，揭示了一个约 200 kDa 的细胞外超折叠，其中八个子域形成一个以螺旋 YD 重复壳为中心的复杂结构。与嗜同性 Teneurin 相互作用和特异性有关的选择性剪接环被暴露并因此准备进行相互作用。壳的 N 端侧通过纤连蛋白-插头结构域组合“插入”，定义了一类新的 YD 蛋白。出乎意料的是，我们发现这些蛋白质广泛存在于现代细菌中，