Figure 2.

NMR studies of GPCR ternary complexes. (a) Complexes of tβ₁AR with an engineered Gs protein (mini-Gs) and G protein-mimicking nanobody, Nb80, compared by NMR. Schematics show β₁AR ternary complexes with an agonist and mini-Gs or nanobody NB80. (b) Superimposed [¹³C,¹H]-HMQC spectra of β₁AR in complex with an agonist and in ternary complexes with either mini-G_S or Nb80. (c) β₂AR-G protein interactions studied by reductive methylation of lysines. Lysines used as NMR probes are shown as orange solid spheres on the structure of the β₂AR-G_S complex (PDB 3SN6). (d) Expanded panels from [¹³C,¹H]-HSQC spectra of β₂AR highlighting chemical shift differences of K140between complexes with G_S and G_i, indicating involvement of ICL2 in differentiating G_S and G_i. (e) Phosphorylated β₂AR and β₂AR in complex with arrestin studied with ε−¹³CH₃-methionine labeling and segmental labeling. (f) Superimposed [¹⁵N,¹H]-HSQC spectra of β₂AR (black) and phosphorylated β₂AR (red) with segmentally-labeled C-terminus. Significant chemical shift changes are indicated with arrows. Panels a and b adapted from reference 17, c and d adapted from reference 19, and e and f adapted from reference 23, with permission.