Homology-based model of the extracellular domain of the taste receptor T1R3
The extracellular ligand binding domain of the sweet receptor T1R3 has been homology-modeled on the basis of the crystal structure of the metabotropic glutamate receptor (mGluR1). The region of the model that corresponds to the ligand binding site of mGluR1 has numerous polar and charged side-chains, consistent with expectations for a site that would respond to poly hydroxy compounds such as mono- and disaccharides. Docking studies show that proposed active conformations of the high-potency sweeteners neotame, superaspartame, and SC-45647 could interact favorably in this binding site, forming ion pairs or ionic hydrogen bonds with His-163, Glu-318, and His-407, in addition to hydrophobic interactions with numerous nonpolar side-chains.