The serine proteinase alpha-thrombin plays a pivotal role in the regulation of blood fluidity, and therefore constitutes a primary target in the treatment of various haemostatic disorders. Haemadin is a slow tight- binding thrombin inhibitor from the land-living leech Haemadipsa sylvestris ...
The serine proteinase alpha-thrombin plays a pivotal role in the regulation of blood fluidity, and therefore constitutes a primary target in the treatment of various haemostatic disorders. Haemadin is a slow tight- binding thrombin inhibitor from the land-living leech Haemadipsa sylvestris. Here we present the 3.1 A crystal structure of the human alpha-thrombin- haemadin complex. The N-terminal segment of haemadin binds to the active site of thrombin, forming a parallel beta-strand with residues Ser214-Gly216 of the proteinase. This mode of binding is similar to that observed in another leech-derived inhibitor, hirudin. In contrast to hirudin, however, the markedly acidic C-terminal peptide of haemadin does not bind the fibrinogen-recognition exosite, but interacts with the heparin-binding exosite of thrombin. Thus, haemadin binds to thrombin according to a novel mechanism, despite an overall structural similarity with hirudin. Haemadin inhibits both free and thrombomodulin-bound alpha-thrombin, but not intermediate activation forms such as meizothrombin. This specific anticoagulant ability of haemadin makes it an ideal candidate for an antithrombotic agent, as well as a starting point for the design of novel antithrombotics.
Related Citations:
Isolation, Sequence Analysis, and Cloning of Haemadin an Anticoagulant Peptide from the Indian Leech Strube, K.-H., Kroeger, B., Bialojan, S., Otte, M., Dodt, J. (1993) J Biol Chem 268: 8590
The Refined 1.9 Angstrom X-Ray Crystal Structure of D-Phe-Pro-Arg-Chloromethylketone Inhibited Human Alpha Thrombin: Structure Analysis, Overall Structure, Electrostatic Properties, Detailed Active Site Geometry and Structure Function Relatioships Bode, W., Turk, D., Karshikov, A. (1992) Protein Sci 1: 426
Organizational Affiliation:
Max-Planck-Institut für Biochemie, D-82152 Martinsried, Department of Biotechnology, BASF Aktiengesellschaft, D-67056 Ludwigshafen, Germany. richards@biochem.mpg.de
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