Extended Data Table 1.

Interaction between GCGR and βarr1, measured by BRET assay

^†All mutations were introduced in the wild-type GCGR or βarr1 (WT). ΔFL, the βarr1 mutant with the turn region of the finger loop (residues 66–73) removed.

^‡The EC₅₀ ratio (EC_50(mutant)/EC_50(WT)) represents the shift between the WT and mutant curves, and characterizes the effect of the mutations on the GCGR-βarr1 interaction.

^§Data are mean ± s.e.m. from at least three independent experiments. *P < 0.05, **P < 0.001, ***P < 0.0001 by one-way analysis of variance followed by Dunnett’s post-test compared to the response of WT. nd, not determined (data for which the concentration response curve could not reach effect saturation within the concentration range tested).

^||The maximal response is reported as a percentage of the maximum effect at the WT.

^¶Sample size, the number of independent experiments performed in technical duplicate.

^#Protein expression levels of GCGR constructs at the cell surface were determined in parallel by flow cytometry with an anti-Flag antibody (Sigma) and reported as per cent compared to the WT from at least three independent measurements performed in technical duplicate.

^††Construct 1, the GCGR construct that was used to determine the structures.

^‡‡Construct 2, the βarr1 construct that was used to determine the structures.