Department of Biological Chemistry, University of California, 615 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.
Department of Chemistry, Umeå University, Umeå, 901 87, Sweden.
Adv Sci (Weinh). 2024 Oct;11(40):e2406494. doi: 10.1002/advs.202406494. Epub 2024 Sep 3.
Oxybutynin (Ditropan), a widely distributed muscarinic antagonist for treating the overactive bladder, has been awaiting a definitive crystal structure for ≈50 years due to the sample and technique limitations. Past reports used powder X-ray diffraction (PXRD) to shed light on the possible packing of the molecule however their model showed some inconsistencies when compared with the 2D chemical structure. These are largely attributed to X-ray-induced photoreduction. Here microcrystal electron diffraction (MicroED) is used to successfully unveil the experimental 3D structure of oxybutynin hydrochloride showing marked improvement over the reported PXRD structure. Using the improved model, molecular docking is applied to investigate the binding mechanism between M muscarinic receptor (MR) and (R)-oxybutynin, revealing essential contacts/residues and conformational changes within the protein pocket. A possible universal conformation is proposed for MR antagonists, which is valuable for future drug development and optimization. This study underscores the immense potential of MicroED as a complementary technique for elucidating unknown pharmaceutical structures, as well as for protein-drug interactions.
奥昔布宁（Ditropan）是一种广泛分布的毒蕈碱拮抗剂，用于治疗膀胱过度活动症，由于样品和技术限制，大约 50 年来一直等待其明确的晶体结构。过去的报告使用粉末 X 射线衍射（PXRD）来阐明分子的可能堆积方式，但与二维化学结构相比，其模型显示出一些不一致。这些主要归因于 X 射线诱导的光还原。在这里，微晶体电子衍射（MicroED）被用于成功揭示盐酸奥昔布宁的实验 3D 结构，与报道的 PXRD 结构相比有了显著的改进。使用改进的模型，进行分子对接以研究 M 毒蕈碱受体（MR）和（R）-奥昔布宁之间的结合机制，揭示了蛋白质口袋内的重要接触/残基和构象变化。提出了一种可能的通用构象，用于 MR 拮抗剂，这对于未来的药物开发和优化具有重要价值。这项研究强调了 MicroED 作为阐明未知药物结构以及蛋白质-药物相互作用的补充技术的巨大潜力。
