Characterization and identification of heparin-induced nonopioid-binding sites for beta-endorphin in human plasma.
We have characterized the specific binding of human beta-endorphin (1-31) to novel binding sites which are formed in human plasma or serum in the presence of heparin. The formation of the binding sites is temperature-dependent and does not occur in the presence of other anticoagulants, such as sodium-EDTA, sodium-oxalate, or sodium-citrate. The specific binding of 125I-beta H-endorphin to heparin-induced binding sites in human plasma is saturable and reversible. It is not inhibited by morphine or naloxone or by various opioid peptides which share their NH2-terminal opioid-active sequence with beta H-endorphin. In contrast, binding is inhibited by the COOH-terminal beta H-endorphin fragment Gly-Glu indicating that binding is to nonopioid sites. Electroimmunoprecipitation techniques revealed that these binding sites are identical with S protein/vitronectin or derivatives thereof. S protein is a plasma alpha 1-glycoprotein involved in attachment and spreading of cells and also in blood coagulation and complement activation. It is possible that the interaction of beta-endorphin with S protein is of physiological significance.
Hildebrand
A
A
Rudolf-Buchheim-Institut für Pharmakologie Justus Liebig-Universität, Giessen, Federal Republic of Germany.
Schweigerer
L
L
Teschemacher
H
H
D001665:Binding Sites; D001667:Binding, Competitive; D006493:Heparin / Q000494:pharmacology*; D006801:Humans; D007123:Immunoelectrophoresis, Two-Dimensional; D011957:Receptors, Opioid / Q000378:metabolism*; D013997:Time Factors; D001615:beta-Endorphin / Q000097:blood*
D011957:Receptors, Opioid; D001615:beta-Endorphin; D006493:Heparin