Figure 5.

Basic structure of the cation-selective pentameric ligand-gated ion channels. (A) Structure-based sequence alignment of the human nAChR and the mouse 5-HT_3A receptor. (B) Schematic view of the X-ray structure of the 5-HT₃ receptor (side and top view). The dashed line represents a long fragment of the cytoplasmic loop (shown only for one front subunit) that was not resolved in the X-ray structure. (C) Structure of one subunit of the 5-HT₃R model. A side view showing the extracellular domains (Cys-loop, α1–2 and β1–10), the transmembrane domains (TMD, TM1–4), and the intracellular domain (ICD).