Naming
The receptors were named using the first letter of the first ligand that was found to bind to them. Morphine was the first chemical shown to bind to mu receptors. The first letter of the drug morphine is m, but in biochemistry there is a tendency to use Greek letters, thus turning the m to μ. In similar manner, a drug known as ketocyclazocine was first shown to attach itself to κ receptors, while the δ receptor was named after the mouse vas deferens tissue in which the receptor was first characterised. An additional opioid receptor was later identified and cloned based on homology with the cDNA. This receptor is known as the nociceptin receptor or OLR (opiate-like receptor) 1.
The opioid receptor types are ~70% identical with differences located at N and C termini. The μ receptor is perhaps the most important. It is thought that the G protein binds to the third intracellular loop of the opioid receptors. Both in mice and humans, the genes for the various receptor subtypes are located on different chromosomes.
Separate subtypes have been identified in human tissue. Research has so far failed to identify the genetic evidence of the subtypes, and it is thought that they arise from post-translational modification of cloned receptor types.
An IUPHAR subcommittee has recommended that appropriate terminology for the 3 classical (μ, δ, κ) receptors, and the non-classical (nociceptin) receptor, should be MOP, DOP, KOP and NOP respectively.
Read more about this topic: Opioid Receptor
Famous quotes containing the word naming:
“Husband,
who am I to reject the naming of foods
in a time of famine?”
—Anne Sexton (1928–1974)
“The night is itself sleep
And what goes on in it, the naming of the wind,
Our notes to each other, always repeated, always the same.”
—John Ashbery (b. 1927)
“See, see where Christ’s blood streams in the firmament!
One drop would save my soul—half a drop! ah, my Christ!—
Ah, rend not my heart for naming of my Christ!—
Yet will I call on him!—O, spare me, Lucifer!—
Where is it now? ‘T is gone; and see where God
Stretcheth out his arm, and bends his ireful brows!—
Mountains and hills, come, come and fall on me,
And hide me from the heavy wrath of God!”
—Christopher Marlowe (1564–1593)