INTERACTION OF C1-INHIBITOR WITH THE C1R AND C1S SUB-COMPONENTS IN HUMAN C1

1. 1.|Insoluble IgG-ovalbumin aggregates were used to bind and activate Cl from human serum. The bound C1 provided a useful reagent for studying the interaction of C1 subcomponents with C1-inhibitor. 2. 2.|C1-inhibitor bound to both subcomponents (C1r and C1s in C1 and formed stable complexes of respective apparent molecular weights 197 000 and 185 000, as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The binding reaction proceeded more readily with C1s than with C1r and was correlated with the inhibition of C1s esterase activity. 3. 3.|At physiological ionic strength, binding of C1-inhibitor to subcomponents C1r and C1s caused release of these subcomponents from the C1-immune aggregates complex, indicating that C1-inhibitor binding decreased the inter-subcomponent binding forces in C1. At low ionic strength, however, this relase did not occur. © 1979.