Kininogen Binding Research Articles

Receptors for high molecular weight kininogen on stimulated washed human platelets

Binding of human high molecular weight kininogen to washed human platelets was studied by measuring platelet-associated radiolabeled ligand in pellets of centrifuged platelets. High molecular weight kininogen was bound to stimulated platelets in the presence of ZnCl2 in a specific and saturable manner. Calcium ions potentiated ligand binding but did not substitute for zinc ions. Optimal binding of high molecular weight kininogen occurred near the plasma concentrations of both zinc and calcium ions. Scatchard analysis yielded 24 200 binding sites for high molecular weight kininogen with an apparent dissociation constant of 20 nM. These studies show that stimulated human platelets can bind many high molecular weight kininogen molecules with high affinity and suggest that the platelet surface may potentially serve as an important site for localizing the initial reactions of the plasma kinin-forming and intrinsic coagulation pathways.

Binding and dissociation of hageman factor, prekallikrein and high molecular weight kininogen in human plasma during contact activation

A kaolin pellet was incubated with human plasma at room temperature and immediately washed to remove all unbound proteins. Whereas in normal plasma, 154 mU(PPAN) of kallikrein was bound to the kaolin surface, in Hageman factor (HF)-deficient plasma or normal plasma preincubated with polybrene the surface-bound kallikrein was undetected, while a trace of prekallikrein was bound to the kaolin surface. Dissociation of kinin and kallikrein from the kaolin surface occurs during varying periods of incubation of the kaolin suspension alone. The dissociation of the surface-bound kallikrein revealed two phases in a 15 min incubation: the first phase of dissociation which rapidly progressed until the kinin liberation reached a plateau was followed by the second phase where the kallikrein was slowly dissociated and kinin was no longer liberated. Treatment of the kaolin suspension with trypsin, plasmin or plasma kallikrein enhanced the kinin liberation and dissociation of kallikrein from the kaolin surface. Kallikrein-kinin-free high molecular weight (HMW) kininogen-activated HF complex, kalli-krein-kinin-free HMW kininogen complex, kallikrein, kinin-free HMW kininogen and two activated HFs were found on Sephacryl S-300 and Sephadex G-100 gel filtrations of the supernatant obtained after a 60 min incubation of the kaolin suspension alone. The ternary complex of kallikrein, kinin-free HMW kininogen and activated HF suggests the presence of prekallikrein-HMW kininogen-HF complex on the kaolin surface.