5gim | pdb_00005gim
Crystal structure of thrombin-avathrin complex
Structural highlights
Disease[THRB_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] Function[THRB_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 PubMedTick saliva is a rich source of antihemostatic compounds. We amplified a cDNA from the salivary glands of the tropical bont tick (Amblyomma variegatum) using primers based on the variegin sequence, which we previously identified as a novel thrombin inhibitor from the same tick species. The transcript encodes a precursor protein comprising a signal peptide and 5 repeats of variegin-like sequences that could be processed into multiple short peptides. These peptides share 31 to 34% identity with variegin. Here, we structurally and functionally characterized one of these peptides named "avathrin." Avathrin is a fast, tight binding competitive inhibitor with an affinity of 545 pM for thrombin and is 4 orders of magnitude more selective towards thrombin than to the other serine proteases of the coagulation cascade. The crystal structure of thrombin-avathrin complex at 2.09 A revealed that avathrin interacts with the thrombin active site and exosite-I. Although avathrin is cleaved by thrombin, the C-terminal cleavage product continues to exert prolonged inhibition. Avathrin is more potent than hirulog-1 in a murine carotid artery thrombosis model. Such precursor proteins that could be processed into multiple thrombin inhibiting peptides appear to be widespread among Amblyomminae, providing an enormous library of molecules for development as potent antithrombotics.-Iyer, J. K., Koh, C. Y., Kazimirova, M., Roller, L., Jobichen, C., Swaminathan, K., Mizuguchi, J., Iwanaga, S., Nuttall, P. A., Chan, M. Y., Kini, R. M. Avathrin: a novel thrombin inhibitor derived from a multicopy precursor in the salivary glands of the ixodid tick, Amblyomma variegatum. Avathrin: a novel thrombin inhibitor derived from a multi-copy precursor in the salivary glands of the ixodid tick, Amblyomma variegatum.,Iyer JK, Koh CY, Kazimirova M, Roller L, Jobichen C, Swaminathan K, Mizuguchi J, Iwanaga S, Nuttall PA, Chan MY, Kini RM FASEB J. 2017 Mar 31. pii: fj.201601216R. doi: 10.1096/fj.201601216R. PMID:28363953[16] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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