Modeling Sweet Protein-Receptor Interactions

描述（由申请人提供）：甜蛋白-受体相互作用建模本研究提案的目标是了解甜蛋白和甜味受体（STR）之间相互作用的性质。STR是T1 R2和T1 R3的异源二聚体，T1 R3是来自C家族的G蛋白偶联受体（GPCR）。越来越多的证据表明，STR对不同的甜味剂具有多个配体结合位点。虽然目前还没有STR的晶体结构，但可以基于适当的模板开发STR的同源性模型。维纳斯捕蝇器模块（VFTM）和富含半胱氨酸的结构域（CRD）可以基于代谢型谷氨酸受体（mGluR）的晶体结构来建模。T1 R2和T1 R3的跨膜结构域（TMD）可以基于牛视紫红质的晶体结构来建模。我们已经成功地使用甜味受体的同源模型，甜味配体与受体的分子对接，以及受体的定点诱变来识别甜味受体的潜在配体结合位点。我们的研究表明，hT 1 R2的VFTM是甜味剂甜菊糖和纽甜的结合位点，而hT 1 R3的TMD是甜味剂甜蜜素和甜味抑制剂lactisole的结合位点。最近的嵌合体和突变研究表明，STR的VFTM和CRD都参与甜蛋白-受体相互作用。为了研究甜蛋白与STR的相互作用，我们建议构建与甜蛋白复合的VFTM-CRD模型。mGluR-I/II的VFTM-CRD的晶体结构最近被解析，这为我们提供了一个理想的模板来开发STR的VFTM-CRD的同源性模型。在这里，我们建议开发几个VFTM-CRD的STR同源性模型，这代表不同的构象状态，基于mGluR模板的晶体结构。改进的STR的VFTM-CRD模型将用于通过布朗动力学（BD）模拟来对接甜蛋白，以了解甜蛋白-受体相互作用。结合定点突变实验和BD对接模拟，我们将确定潜在的复合物的VFTM-CRD的STR与甜蛋白。预测的复合物模型将通过诱变研究进行测试，以评估预测的成功。这些研究将有助于更好地理解STR的功能机制。公共卫生相关性：肥胖和糖尿病在发达国家已达到流行病的程度。用低热量或无热量的甜味剂代替糖可能会有好处。为了设计更有效的甜味剂，在分子水平上理解甜味受体的功能是很重要的.

DESCRIPTION (provided by applicant): Modeling Sweet Protein-Receptor Interactions The goal of this research proposal is to understand the nature of the interactions between sweet proteins and sweet taste receptor (STR). STR is a heterodimer of T1R2 and T1R3, which is a G protein-coupled receptor (GPCRs) from Family C. Growing evidence shows that STR has multiple ligand binding sites for different sweeteners. Although no crystal structure of STR is available at this time, homology models of STR can be developed based on the appropriate templates. The Venus Flytrap Module (VFTM) and Cysteine Rich Domain (CRD) can be modeled based on the crystal structures of metabotropic glutamate receptors (mGluRs). Transmembrane Domain (TMD) of T1R2 and T1R3 can be modeled based on the crystal structure of bovine rhodopsin. We have successfully used homology models of the sweet taste receptors, molecular docking of sweet ligands to the receptors, and site-directed mutagenesis of the receptors to identify potential ligand binding sites of the sweet taste receptor. Our studies show that the VFTM of hT1R2 is the binding site for sweeteners aspartame and neotame, while the TMD of hT1R3 is the binding site for the sweetener cyclamate and the sweet inhibitor lactisole. Recent chimera and mutagenesis studies show that both the VFTM and CRD of STR are involved in sweet protein-receptor interactions. To investigate the interactions of sweet proteins with STR we propose to construct models of the VFTM-CRD in complex with sweet proteins. The crystal structures of the VFTM-CRD of mGluR-I/II, which were resolved recently, provide us an ideal template to develop homology models for the VFTM-CRD of STR. Here we propose to develop several VFTM-CRD of STR homology models, which represent different conformational states, based on the crystal structures of mGluR templates. The refined VFTM-CRD models of STR will be used for docking the sweet proteins by Brownian Dynamics (BD) simulations to understand sweet protein-receptor interactions. In combination with site-directed point mutational experiments and BD docking simulations, we will identify potential complexes of the VFTM-CRD of STR with sweet proteins. The predicted complexes models will be tested via mutagenesis studies to assess the success of the predictions. These studies should lead to a better understanding the function mechanism of STR. PUBLIC HEALTH RELEVANCE: Obesity and diabetes have reached epidemic proportions in developedsocieties. Replacing sugar with low-or non-caloric sweeteners may be of benefit. To design moreeffective sweeteners it is important to understand at the molecularlevel how the sweet taste receptor functions.