Gustducin-coupled receptor implicated in the perception of bitter compounds in the oral cavity and the gastrointestinal tract. Signals through PLCB2 and the calcium-regulated cation channel TRPM5. Expressed in subsets of taste receptor cells of the tongue and palate epithelium and exclusively in gustducin-positive cells. Expressed in 15% taste bud cells in circumvallate and foliate papillae but only in 2% in fungiform papillae. Several bitter taste receptors are expressed in a single taste receptor cell. Belongs to the G-protein coupled receptor T2R family.