4ch8
High-salt crystal structure of a thrombin-GpIbalpha peptide complex
Structural highlights
DiseaseTHRB_HUMAN Defects in F2 are the cause of factor II deficiency (FA2D) [MIM:613679. It is a very rare blood coagulation disorder characterized by mucocutaneous bleeding symptoms. The severity of the bleeding manifestations correlates with blood factor II levels.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] Genetic variations in F2 may be a cause of susceptibility to ischemic stroke (ISCHSTR) [MIM:601367; also known as cerebrovascular accident or cerebral infarction. A stroke is an acute neurologic event leading to death of neural tissue of the brain and resulting in loss of motor, sensory and/or cognitive function. Ischemic strokes, resulting from vascular occlusion, is considered to be a highly complex disease consisting of a group of heterogeneous disorders with multiple genetic and environmental risk factors.[13] Defects in F2 are the cause of thrombophilia due to thrombin defect (THPH1) [MIM:188050. It is a multifactorial disorder of hemostasis characterized by abnormal platelet aggregation in response to various agents and recurrent thrombi formation. Note=A common genetic variation in the 3-prime untranslated region of the prothrombin gene is associated with elevated plasma prothrombin levels and an increased risk of venous thrombosis. Defects in F2 are associated with susceptibility to pregnancy loss, recurrent, type 2 (RPRGL2) [MIM:614390. A common complication of pregnancy, resulting in spontaneous abortion before the fetus has reached viability. The term includes all miscarriages from the time of conception until 24 weeks of gestation. Recurrent pregnancy loss is defined as 3 or more consecutive spontaneous abortions.[14] FunctionTHRB_HUMAN Thrombin, which cleaves bonds after Arg and Lys, converts fibrinogen to fibrin and activates factors V, VII, VIII, XIII, and, in complex with thrombomodulin, protein C. Functions in blood homeostasis, inflammation and wound healing.[15] Publication Abstract from PubMedActivation of platelets by the serine protease thrombin is a critical event in haemostasis. This process involves the binding of thrombin to glycoprotein Ibalpha (GpIbalpha) and cleavage of protease-activated receptors (PARs). The N-terminal extracellular domain of GpIbalpha contains an acidic peptide stretch that has been identified as the main thrombin binding site, and both anion binding exosites of thrombin have been implicated in GpIbalpha binding, but it remains unclear how they are involved. This issue is of critical importance for the mechanism of platelet activation by thrombin. If both exosites bind to GpIbalpha, thrombin could potentially act as a platelet adhesion molecule or receptor dimerisation trigger. Alternatively, if only a single site is involved, GpIbalpha may serve as a cofactor for PAR-1 activation by thrombin. To determine the involvement of thrombin's two exosites in GpIbalpha binding, we employed the complementary methods of mutational analysis, binding studies, X-ray crystallography and NMR spectroscopy. Our results indicate that the peptide corresponding to the C-terminal portion of GpIbalpha and the entire extracellular domain bind exclusively to thrombin's exosite II. The interaction of thrombin with GpIbalpha thus serves to recruit thrombin activity to the platelet surface while leaving exosite I free for PAR-1 recognition. GpIbalpha Interacts Exclusively with Exosite II of Thrombin.,Lechtenberg BC, Freund SM, Huntington JA J Mol Biol. 2013 Dec 5. pii: S0022-2836(13)00738-9. doi:, 10.1016/j.jmb.2013.11.027. PMID:24316004[16] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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