A novel beta-endorphin binding protein. Complement S protein (= vitronectin) exhibits specific non-opioid binding sites for beta-endorphin upon interaction with heparin or surfaces.
Human beta-endorphin (1-31) (beta H-endorphin) was found to specifically interact with purified complement S protein from human plasma. As found by chemical cross-linking beta H-endorphin bound to both, the 65- and 75-kDa molecular mass forms of S protein. The interaction of S protein with heparin as well as the adsorption of S protein to surfaces led to an almost 10-fold increase of specific binding which was due to the exposure of further beta H-endorphin-binding sites. The interaction of beta H-endorphin with S protein bore characteristics of a ligand-receptor interaction, such as time dependence, reversibility, high affinity, saturability, and structural specificity and was mediated through the non-opioid COOH terminus of the beta H-endorphin molecule. beta H-Endorphin binding to S protein was observed at physiological pH or cation concentrations, indicating that the interaction may well occur in vivo. Our results provide conclusive evidence that interactions of S protein with very different effectors led to similar conformational changes which uniformly resulted in exposure of a highly specific beta H-endorphin binding domain on S protein. With S protein as major beta H-endorphin-binding protein in the periphery, the molecular basis of a widespread system of humoral target sites of the neuroendocrine effector appears to be established. In view of S protein involvement in processes of inflammation and wound repair and beta-endorphin effects on immunocompetent cells, the demonstrated S protein-beta H-endorphin interaction appears to be of considerable functional significance.
Hildebrand
A
A
Rudolf-Buchheim-Institut für Pharmakologie, Max-Planck-Gesellschaft, Giessen, Federal Republic of Germany.
Preissner
K T
KT
Müller-Berghaus
G
G
Teschemacher
H
H
D001665:Binding Sites; D001798:Blood Proteins / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D006023:Glycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D010446:Peptide Fragments / Q000378:metabolism; D013388:Succinimides / Q000494:pharmacology; D019096:Vitronectin; D001615:beta-Endorphin / Q000378:metabolism*
D001798:Blood Proteins; D003432:Cross-Linking Reagents; D006023:Glycoproteins; D006025:Glycosaminoglycans; D010446:Peptide Fragments; D013388:Succinimides; D019096:Vitronectin; D001615:beta-Endorphin; D006493:Heparin; C019358:disuccinimidyl suberate