Polar residues in the GLP-1R TM1 are coordinated by Asp-198 (TM2) in the inactive model, orienting key side chains away from TM7 and facilitating tight packing of TM1/TM7. View facing the TM1/TM2 boundary is shown. Key TM1 side chains interacting with Asp-198 are depicted in X-stick representation and labeled. A, inactive GLP-1R model. B, exendin-P5 (ExP5)/GLP-1R structure. C, GLP-1/GLP-1R structure. D, NNC1702/GCGR structure. E, 11-mer agonist/GLP-1R structure. TM helices are labeled in roman numerals.