Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
Nat Commun. 2019 Jun 5;10(1):2452. doi: 10.1038/s41467-019-10279-w.
3-β-hydroxysteroid-Δ, Δ-isomerase, known as Emopamil-Binding Protein (EBP), is an endoplasmic reticulum membrane protein involved in cholesterol biosynthesis, autophagy, oligodendrocyte formation. The mutation on EBP can cause Conradi-Hunermann syndrome, an inborn error. Interestingly, EBP binds an abundance of structurally diverse pharmacologically active compounds, causing drug resistance. Here, we report two crystal structures of human EBP, one in complex with the anti-breast cancer drug tamoxifen and the other in complex with the cholesterol biosynthesis inhibitor U18666A. EBP adopts an unreported fold involving five transmembrane-helices (TMs) that creates a membrane cavity presenting a pharmacological binding site that accommodates multiple different ligands. The compounds exploit their positively-charged amine group to mimic the carbocationic sterol intermediate. Mutagenesis studies on specific residues abolish the isomerase activity and decrease the multidrug binding capacity. This work reveals the catalytic mechanism of EBP-mediated isomerization in cholesterol biosynthesis and how this protein may act as a multi-drug binder.
3-β-羟甾醇-Δ, Δ-异构酶，又称为 Emopamil 结合蛋白（EBP），是一种内质网膜蛋白，参与胆固醇生物合成、自噬、少突胶质细胞形成。EBP 的突变可导致先天性遗传疾病 Conradi-Hunermann 综合征。有趣的是，EBP 结合了大量结构多样的具有药理活性的化合物，导致药物耐药性。在这里，我们报告了两种人 EBP 的晶体结构，一种与抗乳腺癌药物他莫昔芬结合，另一种与胆固醇生物合成抑制剂 U18666A 结合。EBP 采用一种未被报道的折叠方式，涉及五个跨膜螺旋（TMs），形成一个膜腔，呈现一个药理学结合位点，可容纳多种不同的配体。这些化合物利用其带正电荷的氨基来模拟碳正离子固醇中间体。对特定残基的突变会使异构酶活性丧失，并降低多药物结合能力。这项工作揭示了 EBP 介导的胆固醇生物合成中异构化的催化机制，以及这种蛋白质如何作为多药物结合蛋白发挥作用。
