Figure 3.

 Topology of the ghrelin receptor (that is, GHS-R), illustrating the homology with the motilin receptor. Shown is the general two dimensional layout of the putative seven transmembrane domains and the three extracellular loops of the GHS-R. Each dot represents an amino acid residue, using the colour code indicated. The third transmembrane domain (TM3) and the second extracellular loop (ECL2) involved in the activation of, respectively, the ghrelin and motilin receptor are labelled. The figure is based on the alignment published as supplementary material to the paper by Feighner and colleagues¹³ and which can be found at http://www.sciencemag.org/feature/data/1039909.shl.