Extended Data Fig. 3: Structural features of TAS2R14 coupled with G_i1 and G_gust.

a-j, Representative atomic model-fitted EM map for the structure of TAS2R14–G_i1–scFv16 (a-e), and TAS2R14–G_gust–scFv16 (f-j), respectively. Cholesterol and cmpd28.1 which are shown as model-fitted EM maps were observed in the orthosteric pocket and allosteric site, respectively (b,g). Cmpd28.1 in the allosteric site interacts with Hα5 of Gα_i1 (c) and Gα_gust (h). No interactions were observed between ICL1 and Gβ1 in both complexes (d,i). e, W124 of ICL2 forms a hydrogen bond with R32 of αN of Gα in TAS2R14–G_i1–scFv16. The distances between R125 of ICL2 and E28 of αN of Gα in TAS2R14–G_gust–scFv16 is 9 Å indicated by a red arrow. j, E28 of αN of Gα_gust forms a hydrogen bond and an ionic interaction with W124 and R125 of ICL2, respectively. k, Two orthogonal views aligned onto the receptors between TAS2R14–G_gust–scFv16 and TAS2R14–G_i1–scFv16. Black dashed lines indicate two HαN helices distant by 8.5 Å. Models are presented as cylinders for clarity. l-n, Structural comparison of TAS2R14–G_gust with reported structure TAS2R46-miniG_s/gust (PDB 7XP6). This comparison highlights TMs 4, 5, and 7 (l), as well as 6 (m). n, Conserved residue W^3.32 (red circle) of TAS2R14 in the orthosteric pocket is located in the same position as TAS2R46. Cholesterol and strychnine are shown as yellow and purple sticks, respectively. o-r, Structural comparison between TAS2R14–G_i1 and class A GPCR β2AR–G_s (PDB 3SN6) to highlight the conserved motifs in class A GPCRs which are CWxP (o), PIF (p), DRY (q), and NPxxY (r) motif. A large movement of TMs of TAS2R14–G_i1 is shown in the black arrows. A yellow dashed line indicates an interaction between H276^7.49 of TAS2R14–G_i1 and cmpd28.1 (r). s,t Interactions formed between the residues N24^1.50 and S277^7.50 (s) as well as W98^3.41 and P190^5.50 (t).