Front view and top view of the TM domains of the sweet receptor, showcasing the relative positions of the TM helices. Numerical labels denote helices TM1-TM7; circled labels mark the helices that potentially mediate inter-subunit interactions. The TM6 helices of the two subunits of the sweet receptor are ~6 A apart at their closest point (between the Calpha atoms of residue A782 in TAS1R2 and A783 in TAS1R3); the TM6 of TAS1R2 and TM5 of TAS1R3 are ~7 A at their closest point (between the Calpha atoms of residues T763 in TAS1R2 and F749 in TAS1R3).
