beta-Endorphin: characteristics of binding sites in a neuroblastoma--glioma hybrid cell.
Specific binding of human beta-endorphin to NG108-15 cells is described; human beta-[Tyr27-3H2] endorphin was used as the ligand. The binding is time dependent and saturable; Kd = 0.3 nM and ka = 1.8 x 10(8) M-1 min-1. Under the conditions optimal for beta-endorphin binding, leucine-enkephalin has one-fourth to one-third as many binding sites as beta-endorphin and its affinity is 7--10% that of beta-endorphin. Monovalent and divalent cations potently inhibit binding. Trypsin, phospholipase A, and N-ethylmaleimide reduce the ability of NG108-15 cells to bind beta-endorphin. beta-Endorphin analogs are able to fully inhibit the binding of beta-[Tyr27-3H2]endorphin, although enkephalins, morphine, and naloxone inhibit only 50--80%.
D000818:Animals; D002460:Cell Line; D004723:Endorphins / Q000378:metabolism*; D004745:Enkephalins / Q000378:metabolism; D005910:Glioma / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D009374:Neoplasms, Experimental / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*; D013329:Structure-Activity Relationship
D004723:Endorphins; D004745:Enkephalins; D008024:Ligands; D010743:Phospholipids; D011957:Receptors, Opioid