The human T1R family taste receptors include hT1R1, 2, and 3. The T1Rs belong to class-C G protein coupled receptors, and each Class-C GPCR consists of a large N-terminal extracellular domain and a C-terminal 7-transmembrane domain. It is generally known that hT1R1 and hT1R3 form a heteromeric receptor that modulates umami taste transduction and which recognizes umami tastants, while hT1R2 and hT1R3 form a heteromeric receptor that modulates sweet taste transduction and which recognizes sweet tastants. Therefore it is known that the umami taste receptor (hT1R1/hT1R3) and the sweet taste receptor (hT1R2/hT1R3) share a common subunit hT1R3.