Antithrombin activity of the hirudin N-terminal core domain residues 1-43

Hirudin N-terminal core domain residues 1-43 (r-Hir1-43) were prepared from limited proteolysis of recombinant hirudin by V8 Staphylococcal protease followed by purification with reversed-phase HPLC. r-Hir1-43 lacks the putative reactive site of hirudin (Lys47), but binds to thrombin (with Ki of 300 nM) and blocks the catalytic activity of the protease. The structural element which accounts for the thrombin inhibitory activity of r-Hir1-43 is analyzed in this report.