By Increasing the Affinity of Heparin for Fibrin, Zn2+ Promotes the Formation of a Ternary Heparin–Thrombin–Fibrin Complex That Protects Thrombin from Inhibition by Antithrombin

Heparin binds fibrin and, by bridging thrombin onto fibrin, promotes the formation of a ternary heparin-thrombin-fibrin complex that protects thrombin from inhibition by antithrombin. Because thrombin binds γ(A)/γ'-fibrin, a variant with an extended γ-chain, with higher affinity than the bulk γ(A)/γ(A)-fibrin, γ(A)/γ'-fibrin affords bound thrombin more protection from inhibition by antithrombin-heparin. We examined the effect of Zn(2+) on …