Schematic representation of the structures of equine and eel LH/CGR (eLH/CGR and eelLH/CGR, respectively). The locations of the constitutive activating mutations (M398T, L457R, D564G, and D578Y) and the inactivating mutations (D405N, R464H, and Y546F) are indicated (left). In the eelLH/CGR, three constitutively activating mutations (M410T, L469R, and D590Y) and two inactivating mutations (D417N and Y558F) are indicated. Amino acid sequences at the mutated sites in the transmembrane domain and intracellular loop are shown in the eLH/CGR. In eelLH/CGR, the transmembrane domain II, III, V, and VI are shown. EC, extracellular domain; TM, transmembrane domain; IC, intracellular domain; LH/CGR, luteinizing hormone/chorionic gonadotropin receptor.