Motilin (human, porcine)

Motilin (26-47), human, porcine is an endogenous motilin receptor ligand with Ki and EC50 of 2.3 nM and 0.3 nM in a Chinese hamster ovary cell line.

[Bpa1,Ile13]motilin is a full agonist at the motilin receptor that increases intracellular calcium in a concentration-dependent manner (EC50 = 1.5 ± 0.4 nM)[1]. Motilin binds with high affinity (IC50 0.7± 0.2 nM) to receptors on smooth muscle cells. Motilin selectively activates G(q) and G(13), stimulates G alpha(q)-dependent phosphoinositide (PI) hydrolysis and 1,4,5-trisphosphate (IP(3))-dependent Ca2+ release, and increases cytosolic free Ca2+. Motilin induces a biphasic, concentration-dependent contraction (EC50 = 1.0 +/- 0.2 nM), consisting of an initial peak followed by a sustained contraction[2].

References:
[1]. Coulie B, et al. Identification of peptide ligand-binding domains within the human motilin receptor using photoaffinity labeling. J Biol Chem. 2001 Sep 21;276(38):35518-22. Epub 2001 Jul 18.
[2]. Huang J, et al. Signaling pathways mediating gastrointestinal smooth muscle contraction and MLC20 phosphorylation by motilin receptors. Am J Physiol Gastrointest Liver Physiol. 2005 Jan;288(1):G23-31.