This is a domain of seven transmembrane regions that forms the C-terminus of some subclass 3 G-coupled-protein receptors. It is often associated with a downstream cysteine-rich linker domain, NCD3G Pfam:PF07562, which is the human sweet-taste receptor, and the N-terminal domain, ANF_receptor Pfam:PF01094. The seven TM regions assemble in such a way as to produce a docking pocket into which such molecules as cyclamate and lactisole have been found to bind and consequently confer the taste of sweetness [1].

1: Identification of the cyclamate interaction site within the transmembrane domain of the human sweet taste receptor subunit T1R3. Jiang P, Cui M, Zhao B, Snyder LA, Benard LM, Osman R, Max M, Margolskee RF; J Biol Chem. 2005;280:34296-34305. PMID:16076846