The structure of sweet taste receptor (STR), a heterodimer of class C G-protein coupled receptors comprising T1R2 and T1R3 molecules, is still undetermined. In this study, a new enhanced model of the receptor is introduced based on the most recent templates. The improvement, stability, and reliability of the model are discussed in details. Each domain of the protein, i.e., VFTM, CR, and TMD, were separately constructed by hybrid-model construction methods and then assembled to build whole monomers. Overall, 680 ns molecular dynamics simulation was performed for the individual domains, the whole monomers and the heterodimer form of the VFTM orthosteric binding site. The latter’s structure obtained from 200 ns simulation was docked with aspartame; among various binding sites suggested by FTMAP server, the experimentally suggested binding domain in T1R2 was retrieved. Local three-dimensional structures and helices spans were evaluated and showed acceptable accordance with the template structures and secondary structure predictions. Individual domains and whole monomer structures were found stable and reliable to be used. In conclusion, several validations have shown reliability of the new and enhanced models for further molecular modeling studies on structure and function of STR and C GPCRs.

中文翻译：

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介绍一种新的甜味受体模型，一种C类G蛋白偶联受体（C GPCR）。

甜味受体（STR）是C类G蛋白偶联受体的异二聚体，包含T1R2和T1R3分子，其结构尚未确定。在这项研究中，基于最新模板引入了新的受体增强模型。详细讨论了模型的改进，稳定性和可靠性。通过混合模型构建方法分别构建蛋白质的每个结构域，即VFTM，CR和TMD，然后组装以构建完整的单体。总体而言，对VFTM正构结合位点的单个结构域，整个单体和异二聚体形式进行了680 ns的分子动力学模拟。通过200 ns模拟获得的后者的结构与阿斯巴甜对接；在FTMAP服务器建议的各种绑定站点中，实验中提示了T1R2中的结合域。局部三维结构和螺旋跨度进行了评估，并根据模板结构和二级结构预测显示了可接受的范围。发现单个域和整个单体结构是稳定和可靠的。总之，一些验证表明新模型和增强模型的可靠性，可用于对STR和C GPCR的结构和功能进行进一步的分子建模研究。