Binding of fibrin fragments to one-chain and two-chain tissue-type plasminogen activator.
To explore whether fibrin fragments have binding affinity for the tissue-type plasminogen activator (t-PA) molecule, the interactions were studied of (DD)E complex and fragments DD, E1, and E3 with one-chain and two-chain t-PA. For this purpose, a solid-phase binding assay was developed using microtiter plates with nitrocellulose filters. It was found that (DD)E complex and fragments DD and E3 retained the t-PA binding function of the parent fibrin molecule, thus demonstrating that t-PA binds to both the D and E domains of fibrin. Unexpectedly, fragment E1 did not bind t-PA. Fibrin fragments had different binding properties for one-chain and two-chain t-PA. (DD)E complex had the highest and fragment E3 the lowest affinity for one-chain t-PA, both binding curves being consistent with one class of binding sites. However, binding of the fragments with two-chain t-PA was distinguished by more than one class of binding sites, with fragment E3 having the highest affinity for this form of the activator. epsilon-Aminocaproic acid, even at 50 mmol/L concentration, had only minimal effect on binding of (DD)E complex or fragment DD to either one-chain or two-chain t-PA. The potentiating effect of fibrin fragments on plasminogen activation by t-PA was measured by a chromogenic substrate assay. Fragment DD was the most effective stimulator of plasminogen activation by t-PA. In conclusion, (DD)E complex and fragment DD retained most of the regulatory functions of fibrin, which included t-PA binding and t-PA-mediated acceleration of plasminogen activation to plasmin.
Hasan
A A
AA
Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140.
Chang
W S
WS
Budzynski
A Z
AZ
D015119:Aminocaproic Acid / Q000494:pharmacology; D001667:Binding, Competitive; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D010958:Plasminogen / Q000378:metabolism; D010959:Tissue Plasminogen Activator / Q000378:metabolism* / Q000494:pharmacology
D005338:Fibrin Fibrinogen Degradation Products; D010958:Plasminogen; D010959:Tissue Plasminogen Activator; D015119:Aminocaproic Acid