Fig. 2. 5-HT_2β receptors contain key structural elements typical of the 5-HT receptor superfamily and are conserved among arthropods. Predicted protein sequences of 5-HT_2β from Panulirus and Procambarus are aligned with their ortholog from Drosophila and the human 5-HT_2C receptor. Residues identical to the 5-HT_2βPro sequence are indicated with thin lined boxes. Transmembrane domains are indicated with black bars above the sequence and the reference residue for numbering in each is shaded (see Results). Black ovals surround amino acids important for 5-HT ligand binding. Grey boxes surround areas important for G protein coupling or activation. Asterisks above the sequences indicate consensus sites for N-linked glycosylations in crustacean sequences. A black dot indicates the evolutionary change from DRY to DRF in crustacean sequences (see Results).