Smith Alexander D, Page Brent D G, Collier Abby C, Coughtrie Michael W H
Faculty of Pharmaceutical Sciences, The University of British Columbia, 2405 Wesbrook Mall, Vancouver BC V6T 1Z3, Canada.
ACS Omega. 2020 Mar 20;5(12):6872-6887. doi: 10.1021/acsomega.0c00205. eCollection 2020 Mar 31.
The elimination of numerous endogenous compounds and xenobiotics via glucuronidation by uridine-5'-diphosphate glycosyltransferase enzymes (UGTs) is an essential process of the body's chemical defense system. UGTs have distinct but overlapping substrate preferences, but the molecular basis for their substrate specificity remains poorly understood. Three-dimensional protein structures can greatly enhance our understanding of the interactions between enzymes and their substrates, but because of the inherent difficulties in purifying and crystallizing integral endoplasmic reticulum membrane proteins, no complete mammalian UGT structure has yet been produced. To address this problem, we have created a homology model of UGT1A6 using I-TASSER to explore, in detail, the interactions of human UGT1A6 with its substrates. Ligands were docked into our model in the presence of the cosubstrate uridine-5'-diphosphate-glucuronic acid, interacting residues were examined, and poses were compared to those cocrystallized with various plant and bacterial glycosyltransferases (GTs). Our model structurally resembles other GTs, and docking experiments replicated many of the expected UGT-substrate interactions. Some bias toward the template structures' protein-substrate interactions and binding preferences was evident.
通过尿苷-5'-二磷酸糖基转移酶（UGTs）进行葡萄糖醛酸化作用来消除大量内源性化合物和外源性物质，是人体化学防御系统的一个重要过程。UGTs具有不同但重叠的底物偏好，但它们底物特异性的分子基础仍知之甚少。三维蛋白质结构能够极大地增进我们对酶与其底物之间相互作用的理解，然而由于纯化和结晶内质网整合膜蛋白存在固有的困难，目前尚未得到完整的哺乳动物UGT结构。为了解决这一问题，我们利用I-TASSER创建了UGT1A6的同源模型，以详细探究人UGT1A6与其底物的相互作用。在共底物尿苷-5'-二磷酸葡糖醛酸存在的情况下，将配体对接至我们的模型中，检查相互作用的残基，并将构象与那些与各种植物和细菌糖基转移酶（GTs）共结晶的构象进行比较。我们的模型在结构上类似于其他GTs，对接实验重现了许多预期的UGT-底物相互作用。对模板结构的蛋白质-底物相互作用和结合偏好存在一些明显的偏向。
