Figure 5.
Alanine mutation of ECL2 and ECL3 of AMY3R alters functional affinity (log KA) in a peptide- and pathway-specific manner. Functional affinities derived from operational fitting of concentration–response curves in cAMP accumulation (A–E) and pERK (F–J) are displayed as Δlog KA from wild-type. Illustrated is a top view of the AMY3R model with the extracellular surface subject to alanine scanning depicted (combined surface/cpk representation). Mutations that significantly alter peptide functional log KA are colored according to the magnitude of effect, with mutated amino acids without significant alteration to log KA colored gray. Amino acid mutations for which there was an insufficiently robust functional effect to quantify by operational modeling are depicted in black. The receptor ECD and peptide are not shown for clarity, with the CTR TM bundle in blue ribbon and RAMP3 in green ribbon. Red arrows in panels I and J indicate residues at the apex of ECL3 that are affected for Amy and CGRP but not CT peptides.