Characterization of monoclonal antibodies against human protein C specific for the calcium ion-induced conformation or for the activation peptide region.

Abstract Three monoclonal antibodies have been produced that are specific for the activation peptide region m human protein C. These antibodies inhibited the activation of protein C by thrombin and by the thrombin-thrombomodulin complex. A fourth monoclonal antibody specifically recognized the Ca 2+ -stabilized conformation in protein C. This antibody bound both intact protein C and protein C from which the γ-carboxy-glutamic acid-containing region had been removed by limited proteolysis. These results indicate that this antibody recognizes the conformation in protein C stabilized by Ca 2+ bound to the single binding site that is independent of γ-carboxyglutamic acid.