Fig. 4: Illustration of the atomic modeling benefits from improved map resolution.

Cartoon representation of the N-terminal portion of the agonist peptides PACAP38 and GLP-1 bound to their respective receptors. The cryo-EM density maps are drawn at 5-sigma as a blue mesh and highlight the ability to more accurately model side chain and water positions at a higher spatial resolution. a N terminus of the PACAP38 peptide (purple) bound to the PAC1 receptor (pink) at 2.7 Å resolution. There were no reliably detectable water molecule densities in this region of the map. b N terminus of the GLP-1 peptide (dark purple) bound to GLP-1 receptor (light blue) at 2.1 Å resolution. Several water molecule densities were identified and modeled inside the binding pocket of the receptor where they facilitate the interaction with the ligand.