The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Interdisciplinary Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, China.
Nat Commun. 2023 May 3;14(1):2529. doi: 10.1038/s41467-023-38290-2.
Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are two primary components of the eukaryotic membrane and play essential roles in the maintenance of membrane integrity, lipid droplet biogenesis, autophagosome formation, and lipoprotein formation and secretion. Choline/ethanolamine phosphotransferase 1 (CEPT1) catalyzes the last step of the biosynthesis of PC and PE in the Kennedy pathway by transferring the substituted phosphate group from CDP-choline/ethanolamine to diacylglycerol. Here, we present the cryo-EM structures of human CEPT1 and its complex with CDP-choline at resolutions of 3.7 Å and 3.8 Å, respectively. CEPT1 is a dimer with 10 transmembrane segments (TMs) in each protomer. TMs 1-6 constitute a conserved catalytic domain with an interior hydrophobic chamber accommodating a PC-like density. Structural observations and biochemical characterizations suggest that the hydrophobic chamber coordinates the acyl tails during the catalytic process. The PC-like density disappears in the structure of the complex with CDP-choline, suggesting a potential substrate-triggered product release mechanism.
磷脂酰胆碱（PC）和磷脂酰乙醇胺（PE）是真核细胞膜的两种主要成分，在维持膜完整性、脂滴生成、自噬体形成以及脂蛋白形成和分泌方面发挥着重要作用。胆碱/乙醇胺磷酸转移酶 1（CEPT1）通过将 CDP-胆碱/乙醇胺上的取代磷酸基团转移到二酰基甘油上来催化 Kennedy 途径中 PC 和 PE 的生物合成的最后一步。在这里，我们分别以 3.7Å 和 3.8Å 的分辨率呈现了人源 CEPT1 及其与 CDP-胆碱复合物的冷冻电镜结构。CEPT1 是一个二聚体，每个单体有 10 个跨膜片段（TMs）。TMs 1-6 构成一个保守的催化结构域，内部有一个疏水性腔容纳 PC 样密度。结构观察和生化特性表明，该疏水性腔在催化过程中协调酰基尾部。在与 CDP-胆碱的复合物结构中，PC 样密度消失，提示存在潜在的底物触发的产物释放机制。
