opioid receptor subtype kappa, member of the class A family of seven-transmembrane G protein-coupled receptors
The kappa-opioid receptor binds the opioid peptide dynorphin as the primary endogenous ligand. The opioid receptor family is composed of four major subtypes: mu (MOP), delta (DOP), kappa (KOP) opioid receptors, and the nociceptin/orphanin FQ peptide receptor (NOP). They are distributed widely in the central nervous system and respond to classic alkaloid opiates, such as morphine and heroin, as well as to endogenous peptide ligands, which include dynorphins, enkephalins, endorphins, endomorphins, and nociceptin. Opioid receptors are coupled to inhibitory G proteins of the G(i/o) family and involved in regulating a variety of physiological functions such as pain, addiction, mood, stress, epileptic seizure, and obesity, among many others.
Comment:based on the structures of some class A family members with bound ligands (peptides or chemicals), agonists, or antagonists
Comment:Opioid receptors respond to classical opioid alkaloids such as morphine and heroin, as well as to endogenous peptide ligands like dynorphins, enkephalins, endorphins, endomorphins and nociceptin.
Comment:Small-molecule chemical ligands tend to bind deeper within the receptor core, compared to a peptide ligand neurotensin, which binds towards the extracellular surface of its receptor.
Structure:4DJH: Human kappa-opioid receptor in complex with antagonist JDTic, contacts at 4A.
Jiyao W et al.(2023). "The conserved domain database in 2023.",