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The structural elements of hirudin which bind to the fibrinogen recognition site of thrombin are exclusively located
1Pharmaceuticals Research Laboratories, Ciba-Geigy Ltd., Basel, Switzerland.
Six lysyl residues of human thrombin (LysB21, LysB52, LysB65, LysB106, LysB107 and LysB154) have been previously shown to participate in the binding site of hirudin, a thrombin-specific inhibitor [(1989) J. Biol. Chem. 264, 7141-7146]. In this report, we attempted to delineate the region of hirudin which binds to these basic amino acids of thrombin. Using the N-terminal core domains (r-Hir1-43 and r-Hir1-52) derived from recombinant hirudins and synthetic C-terminal peptides (Hir40-65 and Hir52-65)--all fragments form complexes with thrombin--we are able to demonstrate that the structural elements of hirudin which account for the shielding of these 6 lysyl residues are exclusively located within the acidic C-terminal region. Since hirudin C-terminal peptides were shown to bind to a non-catalytic site of thrombin and inhibit its interaction with fibrinogen [(1987) FEBS Lett. 211, 10-16], our data consequently imply that these 6 lysyl residues are constituents of the fibrinogen recognition site of thrombin.
Six lysyl residues of human thrombin (LysB21, LysB52, LysB65, LysB106, LysB107 and LysB154) have been previously shown to participate in the binding site of hirudin, a thrombin-specific inhibitor [(1989) J. Biol. Chem. 264, 7141-7146]. In this report, we attempted to delineate the region of hirudin which binds to these basic amino acids of thrombin. Using the N-terminal core domains (r-Hir1-43 and r-Hir1-52) derived from recombinant hirudins and synthetic C-terminal peptides (Hir40-65 and Hir52-65)--all fragments form complexes with thrombin--we are able to demonstrate that the structural elements of hirudin which account for the shielding of these 6 lysyl residues are exclusively located within the acidic C-terminal region. Since hirudin C-terminal peptides were shown to bind to a non-catalytic site of thrombin and inhibit its interaction with fibrinogen [(1987) FEBS Lett. 211, 10-16], our data consequently imply that these 6 lysyl residues are constituents of the fibrinogen recognition site of thrombin.