Fig. 3: Comparison of Gα_i1 and its nucleotide-binding pocket across conformational states preceding GDP release.

a, Overlay of Gα_i subunit structures across receptor-free GDP–Gα_i1β₁γ₂ (PDB ID 1GP2), latent, engaged, unlatched and primed states. b, Contact map highlighting interactions of Gα_i residues with GDPβS across the five observed states. Contacts were determined by LigPlot⁺ (ref. ⁵³) and the number of contacts is colour coded for the respective state and residue (light red 0 to dark blue more than 7 interactions per residue with GDP). Boxes (solid) in the first row represent backbone interactions. Boxes (solid) in the second row represent side-chain interactions. Boxes (dashed) in the third row represent hydrogen bonds (H bonds): only the total numbers of hydrogen bonds are shown in the centre. c, Overview of the hydrophobic core of Gα_i, including α5 helix, α1 and α3, highlighting conformational changes across transition from latent to engaged state. Specifically, the translation of the α5 helix towards the receptor core, and a partial retraction of the TCAT loop. d, Overview of the hydrophobic core of Gαi, including α5 helix, TCAT loop, α1 and α3, highlighting conformational changes across three conformational states (engaged, unlatched, primed), and most importantly translation and rotation of α5, resulting in retraction of the TCAT loop, and rearrangement of β6. e, αF transition and α1 movement across latent, engaged and primed states, required for GDP release. f, Successive change in relative angle between Gα and Gβ subunits. g, Comparison of SwI, P loop and SwIII across states. h, Nucleotide-binding pocket, highlighting rearrangements of E43 and R178 from a closed ‘seatbelt’ conformation in GDP–Gα_i1β₁γ₂ (PDB ID 1GP2) to latent state. i, Nucleotide-binding pocket, highlighting R178 protruding towards Mg²⁺ binding pocket in the engaged state, compared with GTP-bound Gα_i1 (PDB ID 1GIL). j, α1, TCAT and P loop transitions towards the nucleotide-free state.