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Updated: Aug 23, 2025

Real-time In Vitro Monitoring of Odorant Receptor Activation by an Odorant in the Vapor Phase
Published on: April 23, 2019
The Third Extracellular Loop of Mammalian Odorant Receptors Is Involved in Ligand Binding
Tammy Shim1, Jody Pacalon2, Won-Cheol Kim1
1Department of Brain Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 711-873, Korea.
Abstract:
Mammals recognize chemicals in the air via G protein-coupled odorant receptors (ORs). In addition to their orthosteric binding site, other segments of these receptors modulate ligand recognition. Focusing on human hOR1A1, which is considered prototypical of class II ORs, we used a combination of molecular modeling, site-directed mutagenesis, and in vitro functional assays. We showed that the third extracellular loop of ORs (ECL3) contributes to ligand recognition and receptor activation. Indeed, site-directed mutations in ECL3 showed differential effects on the potency and efficacy of both carvones, citronellol, and 2-nonanone.
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