9.A.14.10.4
Dimeric oxytosin receptor, OxtR, of 389 aas and 7 TMSs. Superpotent behavior follows from the binding of oxytosin receptor-specific bivalent ligands to dimeric receptors based on a TMS1-TMS2 interface, and in this arrangement, only analogues with a well-defined spacer length (approximately 25 Å) precisely fit inside a channel-like passage between the two protomers of the dimer (Busnelli et al. 2016). The oxytocin receptor (OXTR) is involved in parturition and lactation of mammals as well as  their emotional and social behaviors. Cholesterol acts on OXTR as an allosteric modulator, inducing a high-affinity state for orthosteric ligands. Stable binding of cholesterol to the receptor when it adopts an orthosteric ligand-bound state  preserves the cholesterol-dependent activity of the receptor (Lemel et al. 2021).