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. Interacts with RTP3 and RTP4. Expressed in subsets of taste receptor cells of the tongue and palate epithelium and exclusively in gustducin-positive cells. Expressed in the antrum and fundus (part of the stomach), duodenum and in gastric endocrine cells. Several bitter taste receptors are expressed in a single taste receptor cell. Belongs to the G-protein coupled receptor T2R family.