The Pharmacology and Signaling of Bitter, Sweet, and Umami Taste Sensing

The human T1R2-T1R3 sweet receptor. The functional receptor is a heterodimer composed of a T1R2 and a T1R3 class C GPCR. Binding for most sweet ligands occurs on the T1R2 unit. Sugars may interact with the large N termini of both T1R2 and T1R3, whereas the sweet protein brazzein binds to a cysteine-rich region of the T1R3 N terminus. Cyclamate and the sweet-taste inhibitor lactisole bind to the transmembrane-spanning domains of T1R3.