Notable positions of the MRGX1-type receptors visualized in the crystal structure of bovine rhodopsin.

Positions 2.56, and 2.60 and 3.29 are under positive selection pressure and shown in white −3.29 is a key position, while 2.56 and 2.60 are not. Residues at two key positions, 3.32 and Val 204 5.39 are under negative selection pressure and shown in green. Residues at remaining 7 key positions are not under strong selective pressure are shown in yellow. Those positions are 3.33, 4.60, 5.35, 5.42, 6.55, 7.35 and 7.39. The figure is relative to the structure of bovine rhodopsin published by Schertler and coworkers (PDB ID: 1GZM) [70]. The notable positions are represented through spheres centered on the Cα atoms of the corresponding rhodopsin residues. The backbone of the receptor is schematically represented as a ribbon, colored with continuum spectrum that transitions from red to purple moving from the N-terminus to the C-terminus (TM1: dark orange; TM2: light orange; TM3: yellow; TM4: yellow/green; TM5: green; TM6: cyan; TM7: blue/purple).