MECHANISM OF AGONISM-ANTAGONISM OF SWEET TASTE RECEPTORS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 本方案的目标是建立人类甜味受体跨膜(TM)结构域中激动剂和拮抗剂可能结合位点的分子模型，人T1R2(HT1R2)和hT1R3的异源二聚体属于G蛋白偶联受体家族。最近牛视紫质的晶体结构为构建GPCRs模型提供了机会，这些模型已被证明是这些受体选择性和活性的可靠预测因子。我们假设：1.激动剂和拮抗剂结合在同一个TM口袋中；2.通过结合，激动剂诱导特定的构象变化导致激活，并被拮抗剂结合所阻断。我们将通过计算分子对接确定人工甜味剂(如甜蜜素)和抑制剂(如乳糖醇)受体中的结合口袋，并通过诱变研究测试其有效性。实验证实的模型将用于对占用和未占用的受体进行分子动力学模拟，以加深对甜味反应激活和抑制机制的分子基础的理解。从模拟中推断出的机制将通过突变来测试，这些突变旨在产生一个具有结构性活性的受体。这些研究将有助于更好地了解受体的功能，并将为设计新型甜味调节剂提供基础。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goal of the current proposal is to develop molecular models of possible binding sites for agonists and antagonists within the transmembrane (TM) domain of the human sweet taste receptor, the heterodimer of human T1R2 (hT1R2) and hT1R3, which belongs to the G protein coupled receptor family. Recent crystal structures of bovine rhodopsin provide an opportunity to construct models of GPCRs that have been shown to be reliable predictors of selectivity and of activity in these receptors. We hypothesize that: 1. Agonists and antagonists bind in the same TM pocket; and 2. Through binding, agonists induce specific conformational changes that lead to activation and are blocked by the binding of antagonists. We will identify the binding pockets in the receptor for artificial sweeteners, (e.g., cyclamate) and inhibitors, (e.g., lactisole) by computational molecular docking and test their validity via mutagenesis studies. The experimentally confirmed models will be used to conduct molecular dynamics simulations on occupied and unoccupied receptors to develop an understanding of the molecular basis for activation and inhibition mechanisms of the sweet taste response. The mechanisms inferred from simulations will be tested by mutations designed to produce a constitutively active receptor. These studies should lead to a better understanding of receptor function and will provide the basis for design of novel sweet taste modulators.