1.A.9.2.5
The 5-hydroxytryptamine (serotonin) receptor 3B, HTR3B, of 441 aas and 4 or 5 TMSs in a 1 (N-terminal) + 2 or 3 (residues 240 - 320) + 1 TMS (C-terminal). This is one of the several different receptors for 5-hydroxytryptamine (serotonin), a biogenic hormone that functions as a neurotransmitter, a hormone, and a mitogen. This receptor is a ligand-gated ion channel, which when activated, causes fast, depolarizing responses. It is a cation-specific, but otherwise relatively nonselective, ion channel (Kelley et al. 2003). The MX helix on the cytoplasmic side of the membrane can modulate the function of the receptor, and its interactions with membrane lipids play a major role (Mocatta et al. 2022).