title: Beta-endorphin: interaction with specific nonopioid binding sites on EL4 thymoma cells.
abstract: Binding of 125I-labeled camel beta-endorphin (125I-beta C-endorphin) to cells of several mouse thymoma cell lines was examined and was highest to EL4 cells. 125I-beta C-endorphin binding to EL4 cells was temperature-dependent; it was further characterized at 4 degrees C and exhibited saturability, complete reversibility, structural specificity and pH-dependence. 125I-beta C-endorphin binding was not inhibited by the opioid pentapeptides [Leu] enkephalin or [Met] enkephalin (which share common sequences with the N-terminus of beta C-endorphin) or by the N-terminal beta C-endorphin fragments beta C-endorphin (1-16) or beta C-endorphin (1-27). In contrast, binding was inhibited by beta C-endorphin (1-31), indicating that beta C-endorphin binding to EL4 cells was with a C-terminal beta C-endorphin segment. We suggest that binding of beta-endorphin to such nonopioid binding sites may precede its apparent effects on the proliferation of T-lymphocytes (5,6).
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004723:Endorphins / Q000378:metabolism / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D051379:Mice; D011957:Receptors, Opioid / Q000187:drug effects* / Q000378:metabolism; D013696:Temperature; D013945:Thymoma / Q000378:metabolism*; D013953:Thymus Neoplasms / Q000378:metabolism*; D013997:Time Factors; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D011957:Receptors, Opioid; D001615:beta-Endorphin