title: Crystal structure of the human alpha-thrombin-haemadin complex: an exosite II-binding inhibitor.
abstract: 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.
authors.affiliation: Max-Planck-Institut für Biochemie, D-82152 Martinsried, Department of Biotechnology, BASF Aktiengesellschaft, D-67056 Ludwigshafen, Germany. richards@biochem.mpg.de
authors.forename: J L
authors.initials: JL
authors.lastname: Richardson
authors.forename: B
authors.initials: B
authors.lastname: Kröger
authors.forename: W
authors.initials: W
authors.lastname: Hoeffken
authors.forename: J E
authors.initials: JE
authors.lastname: Sadler
authors.forename: P
authors.initials: P
authors.lastname: Pereira
authors.forename: R
authors.initials: R
authors.lastname: Huber
authors.forename: W
authors.initials: W
authors.lastname: Bode
authors.forename: P
authors.initials: P
authors.lastname: Fuentes-Prior
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006629:Hirudins / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007447:Invertebrate Hormones / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D007865:Leeches / Q000737:chemistry; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D012996:Solutions; D013917:Thrombin / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism
chemical_list: D006629:Hirudins; D007447:Invertebrate Hormones; D046911:Macromolecular Substances; D012996:Solutions; C080680:haemadin; D013917:Thrombin