Fig. 1.

Topology model of the rat adenine receptor. Mutated amino acid residues presumed to be involved in ligand binding and the potential N-terminal signal peptide are shown as hexagons using the following color code: gray, potential signal peptide; blue, Phe110^3.24; red, Asn115^3.29; magenta, Asn173^4.60; purple, Phe179^45.39 (Phe179 is located in ECL2 which also includes the highly conserved residue Cys190^45.50); orange, Asn194^5.40; cyan, Phe195^5.41; green, Leu201^5.47; brown, His252^6.54; and dark green, Tyr268^7.32