Figure 3. Binding of the Gα α5 helix in GPCR-G protein complexes.

(A) Overview of a subset of GPCR-G protein complexes used for this analysis. For a complete list of the complexes used, see Figure 3—figure supplement 2. The complexes are shown from the cytoplasmic side, and the black pentagons connecting TM2-3-5-6-7 delineate the G protein-binding interface. Receptors are represented in ribbons with their TM helices numbered. (B) The red surfaces depict the contact area (within a distance of 4 Å) between the receptor and the α5 helix of Gα (C) Schematic representation of the α5 helix in Gi- and Gs-subtypes. The residues highlighted, and their respective binding site to the receptor, are conserved among all Gi, and Gs, complexes analyzed. All contacts retrieved from this analysis are reported in Figure 3—figure supplement 2. (D) Position of Gi- and Gs-specific contacts shown in the rhodopsin-Gi (this work, PDB id: 6QNO) and the β₂AR-Gs (PDB id: 3SN6) complexes. The cytoplasmic side of the receptors is depicted as gray surface. Red lines mark the border between TM5 and TM6 and delineate H8. (E) Cytoplasmic view of GPCR-G protein complexes showing the interaction between H5.17 (orange spheres) and TM5 and TM6. From left to right, the structures (PDB ids) correspond to: this work, 6G79, 6DDE, 6D9H, 3SN6, 6GDG, 5UZ7, and 5VAI. Throughout the analysis, contacts are defined as atomic distances smaller than 4 Å.

Figure 3—figure supplement 1. Residue-residue contact list between GPCRs and Gα H5.

11–26 within 4 Å.

Figure 3—figure supplement 2. Residue-residue contacts between GPCRs and Gα H5.

11–26.

Figure 3—figure supplement 3. Contacts observed between ICL2/ICL3 and the Gα subunit.

(A) Intracellular loop (ICL) 2 and 3 in the EM density map (B) Schematic overview of the contacts between the intracellular loops of the receptor and Gα. (C) Sequence of ICL2 in the available structures of the GPCR-G protein complexes. Residues that contact to regions of the G protein other than the α5 helix are highlighted in cyan. (D) Same as panel B, but for ICL3. Residues missing from the structure are marked in gray. The residues are numbered using the Ballesteros-Weinstein scheme.

Figure 3—figure supplement 4. Residue-residue contacts between ICL2/3 and Gα.

Contacts at the regions of ICL2 and 3 are identified using a 4 Å cut-off. Residue-residue contacts are listed for the regions of ICL2 (top panel) and ICL3 (bottom panel). The residues of Gα are numbered following the common Gα protein numbering (CGN). Contacts observed in the individual structures are noted as colored bullet symbols (blue – Gi-coupled receptors; green – Gs-coupled, class A receptors; magenta – Gs-coupled, class B receptors).

Figure 3—figure supplement 5. Region near ICL2 in available structures.

View of the existing GPCR-G protein complex structures centered at the ICL2 region. The structures are aligned to the Cα atoms of rhodopsin. The regions of the G protein involved in contacting ICL2 are the αN/β1 and β2/β3 turns, and the α5 helix.