title: Structure of activated thrombin-activatable fibrinolysis inhibitor, a molecular link between coagulation and fibrinolysis.
abstract: Thrombin-activatable fibrinolysis inhibitor (TAFI) is a metallocarboxypeptidase (MCP) that links blood coagulation and fibrinolysis. TAFI hampers fibrin-clot lysis and is a pharmacological target for the treatment of thrombotic conditions. TAFI is transformed through removal of its prodomain by thrombin-thrombomodulin into TAFIa, which is intrinsically unstable and has a short half-life in vivo. Here we show that purified bovine TAFI activated in the presence of a proteinaceous inhibitor renders a stable enzyme-inhibitor complex. Its crystal structure reveals that TAFIa conforms to the alpha/beta-hydrolase fold of MCPs and displays two unique flexible loops on the molecular surface, accounting for structural instability and susceptibility to proteolysis. In addition, point mutations reported to enhance protein stability in vivo are mainly located in the first loop and in another surface region, which is a potential heparin-binding site. The protein inhibitor contacts both the TAFIa active site and an exosite, thus contributing to high inhibitory efficiency.
authors: Institut de Biotecnologia i de Biomedicina and Departament de Bioquímica i Biologia Molecular (Facultat de Ciències), Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
authors: Laura
authors: L
authors: Sanglas
authors: Center for Insoluble Protein Structures at the Department of Molecular Biology, Science Park, University of Århus, Gustav Wieds Vej 10c, DK-8000 Århus C, Denmark.
authors: Zuzana
authors: Z
authors: Valnickova
authors: Department of Structural Biology at the Molecular Biology Institute of Barcelona, CSIC, Barcelona Science Park, c/Balidiri Reixach, 10-12 and 15-21, E-08028, Spain.
authors: Joan L
authors: JL
authors: Arolas
authors: Institut de Biotecnologia i de Biomedicina and Departament de Bioquímica i Biologia Molecular (Facultat de Ciències), Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
authors: Irantzu
authors: I
authors: Pallarés
authors: Department of Structural Biology at the Molecular Biology Institute of Barcelona, CSIC, Barcelona Science Park, c/Balidiri Reixach, 10-12 and 15-21, E-08028, Spain.
authors: Tibisay
authors: T
authors: Guevara
authors: Department of Structural Biology at the Molecular Biology Institute of Barcelona, CSIC, Barcelona Science Park, c/Balidiri Reixach, 10-12 and 15-21, E-08028, Spain.
authors: Maria
authors: M
authors: Solà
authors: Center for Insoluble Protein Structures at the Department of Molecular Biology, Science Park, University of Århus, Gustav Wieds Vej 10c, DK-8000 Århus C, Denmark.
authors: Torsten
authors: T
authors: Kristensen
authors: Center for Insoluble Protein Structures at the Department of Molecular Biology, Science Park, University of Århus, Gustav Wieds Vej 10c, DK-8000 Århus C, Denmark.
authors: Jan J
authors: JJ
authors: Enghild
authors: Institut de Biotecnologia i de Biomedicina and Departament de Bioquímica i Biologia Molecular (Facultat de Ciències), Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain. Electronic address: francescxavier.aviles@uab.es.
authors: Francesc X
authors: FX
authors: Aviles
authors: Department of Structural Biology at the Molecular Biology Institute of Barcelona, CSIC, Barcelona Science Park, c/Balidiri Reixach, 10-12 and 15-21, E-08028, Spain. Electronic address: xgrcri@ibmb.csic.es.
authors: F Xavier
authors: FX
authors: Gomis-Rüth
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001681:Biological Assay; D001777:Blood Coagulation; D025901:Carboxypeptidase B2 / Q000737:chemistry* / Q000302:isolation & purification; D002417:Cattle; D018360:Crystallography, X-Ray; D005342:Fibrinolysis; D006493:Heparin / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013816:Thermodynamics
chemical_list: D006493:Heparin; D025901:Carboxypeptidase B2