The serotonin-gated 5-HT3 receptor is a ligand-gated ion channel. Its location at the synapse in the central and peripheral nervous system has rendered it a prime pharmacological target, for example, for antiemetic drugs that bind with high affinity to the neurotransmitter binding site and prevent the opening of the channel. Advances in structural biology techniques have led to a surge of disclosed three-dimensional receptor structures; however, solving ligand-bound high-resolution 5-HT3 receptor structures has not been achieved to date. Ligand binding poses in the orthosteric binding site have been largely predicted from mutagenesis and docking studies. We report the synthesis of a series of photo-cross-linking compounds whose structures are based on the clinically used antiemetic drug granisetron (Kytril). These displaced [3H]granisetron from the orthosteric binding site with low nanomolar affinities and showed specific photo-cross-linking with the human 5-HT3 receptor. Detailed analysis by protein-MS/MS identified a residue (Met-228) near the tip of binding loop C as the covalent modification site.

中文翻译：

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使用光交联拮抗剂绘制人 5-HT3 受体的正构结合位点。

5-羟色胺门控 5-HT3 受体是一种配体门控离子通道。它位于中枢和周围神经系统的突触处，使其成为主要的药理学靶点，例如，用于以高亲和力结合神经递质结合位点并阻止通道打开的止吐药物。结构生物学技术的进步导致公开的三维受体结构激增；然而，迄今为止尚未实现解决配体结合的高分辨率 5-HT3 受体结构。正构结合位点中的配体结合位点已在很大程度上从诱变和对接研究中预测。我们报告了一系列光交联化合物的合成，其结构基于临床使用的止吐药格拉司琼 (Kytril)。这些以低纳摩尔亲和力从正构结合位点置换的[3H]格拉司琼并显示出与人5-HT3受体的特异性光交联。通过蛋白质-MS/MS 进行的详细分析确定了结合环 C 尖端附近的一个残基 (Met-228) 作为共价修饰位点。