A candidate taste receptor gene near a sweet taste locus

The mechanisms underlying sweet taste in mammals have been elusive. Althoug h numerous studies have implicated G proteins in sweet taste detection, the expected G protein-coupled receptors have not been found. Here we describe a candidate taste receptor gene, T1r3, that is located at or near the mous e Sac locus, a genetic locus that controls the detection of certain sweet t astants. T1R3 differs in amino acid sequence in mouse strains with differen t Sac phenotypes ('tasters' versus 'nontasters'). In addition, a perfect co rrelation exists between two different T1r3 alleles and Sac phenotypes in r ecombinant inbred mouse strains. The T1r3 gene is expressed in a subset of taste cells in circumvallate, foliate and fungiform taste papillae. In circ umvallate and foliate papillae, most T1r3-expressing cells also express a g ene encoding a related receptor, T1R2 raising the possibility that these ce lls recognize more than one ligand, or that the two receptors function as h eterodimers.