Fig. 5.

Number and distribution of mutations within topological domains. The number of variants (x-axis) per topological domain (y-axis) as defined by the conserved class A GPCR molecular architecture of seven TM helices (TM1 to 7 in red), three extracellular loops (ECL 1 to 3 in green), three intracellular loops (ICL 1 to 3 in blue), and N- and C-terminal regions (in gray). NCR, non-coding regions. The darkest regions on the y-axis bars correspond to missense substitutions. The cartoon model in the lower right exemplifies the extent and arrangement of the topological regions according to the crystallographic structure of rhodopsin (PDBid: 4J4Q, retinal is shown in yellow vdW spheres)