作者: H R Colten , J Melamed , B F Tack , M A Arnaout
DOI:
关键词: Trypsin 、 Trypsinization 、 Cleavage (embryo) 、 Chemistry 、 Biochemistry 、 Cooperativity 、 Binding site 、 Receptor–ligand kinetics 、 Receptor 、 Dimer
摘要: The interaction of C3b receptor with C3b, the major cleavage product C3, elicits important biologic functions, such as enhanced phagocytosis and release cellular enzymes. We determined binding kinetics isotherm C3b-receptor by using human cells fluid phase generated trypsin purified native C3. 125I labeled was separated into 2 molecular species, a dimer monomer column chromatography. found that dimeric bound to erythrocyte receptors an affinity more than 25 times monomer. did not bind sheep red blood cells, which lack receptor, nor trypsinized or 2-mercaptoethanol treated normal methods for abrogating immune adherence activity. Binding specific, saturable (about 90 ng maximally per 1 X 10(9) cells), reversible (in presence 100-fold molar excess unlabeled ligand), moderate (Kd about 9.53 nM). equilibrium constants were similar various tested. characterized rapid on off rates exhibit ligand cooperativity. This specific reached steady state within 10 15 min at 0 degrees C; 50% specifically dissociated from its site in approximately C. density polymorphonuclear leukocytes, monocytes, B lymphocyte-enriched preparations 360, 20,000, 30,000, 21,000 receptors/cell, respectively.