title: beta-Endorphin: evidence for the existence of opioid and non-opioid binding components for the tritiated human hormone in NG108-15 cells.
abstract: Human beta-endorphin (beta h-EP) binding on neuroblastoma X glioma hybrid NG108-15 cells using tritiated human beta endorphin (3H-beta h-EP) as a primary ligand was found to have a component which was not displacable with [D-Ser2 )-Leu-enkephalin-Thr6 (DSLET). The beta h-EP binding on these cells after saturation of the delta opiate sites with 200 nM DSLET was further characterized with synthetic beta h-EP analogs. The nonopioid binding site appears to recognize beta h-EP-(6-31), beta h-EP-(21-31) and beta h-EP-(28-31). Under these conditions, these COOH-terminal segments fully displace the tritiated beta h-EP. However, beta h-EP-(1-27) does not further displace 3H-beta h-EP in the presence of DSLET. The fact that a combination of DSLET and beta h-EP-(6-31) results in a full displacement of 3H-beta h-EP provides direct evidence for the existence of two binding sites for beta h-EP in NG108-15 cells, one recognizing the NH2-terminal enkephalin sequence and the other the non-opioid COOH-terminal segment.
mesh_terms: D001667:Binding, Competitive; D002460:Cell Line; D004723:Endorphins / Q000378:metabolism*; D005910:Glioma; D006801:Humans; D006822:Hybrid Cells; D009447:Neuroblastoma; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D011957:Receptors, Opioid / Q000302:isolation & purification*; D014316:Tritium; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D011957:Receptors, Opioid; D014316:Tritium; D001615:beta-Endorphin