Opioid receptors

Opioid receptors (OpR) are a Subfamily A4 G protein-coupled receptors with opioids as ligands^[1]. OpR types are classified according to the ligands which bind to them.

• The μ-opioid receptor binds morphine. For more details on μ-opioid receptor see
  
  • Mu Opioid Receptor Bound to a Morphinan Antagonist
  • μ Opioid Receptors
  • Mu Opioid Receptor.
  • 6dde μ-opioid receptor: G protein complex
    
• The κ-opioid receptor binds opium-type ligands. For details see Student Project 3 for UMass Chemistry 423 Spring 2015.
  
• The δ-opioid receptor binds enkephalins. For details see Delta opioid receptor.
• The Nociceptin/orphanin FQ opioid receptor binds the heptadecapeptide orphanin^[2].

• Tutorial: The opioid receptor, a molecular switch

You can check out the in the window on the right. It shows the mu opioid receptor bound to a peptide ligand and a G protein . The G protein ("G" because it binds to GTP) consists of three parts A , B , and C ).