9c50
Replacement of a single residue changes the primary specificity of thrombin
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 PubMedBACKGROUND: Thrombin prefers substrates carrying Arg at the site of cleavage (P1) because of the presence of D189 in the primary specificity (S1) pocket but can also cleave substrates carrying Phe at P1. The structural basis of this property is unknown. OBJECTIVES: Solve the X-ray structure of thrombin bound to a ligand carrying Phe at P1 and investigate the effects of replacing D189. METHODS: X-ray crystallography is used to solve the structure of thrombin bound to the irreversible inhibitor H-D-Phe-Pro-Phe-CH(2)Cl (PPPCK). Residue D189 is mutated to Ala, Lys, Phe, and Ser. RESULTS: The X-ray structure of the thrombin-PPPCK complex is solved at 2.5 A resolution and compared to the structure of thrombin bound to H-D-Phe-Pro-Arg-CH(2)Cl (PPACK). PPPCK binds to thrombin in a conformation similar to that of PPACK, but Phe at P1 makes no contacts with D189. Replacement of D189 with Ala, Lys, Phe, or Ser reverses both substrate preference and stability enhancement from Arg to Phe. CONCLUSION: D189 in the S1 pocket confers thrombin "trypsin-like" specificity for Arg at P1. However, the S1 pocket is wide enough to also enable "chymotrypsin-like" specificity for Phe at P1. Consistent with these structural features, a single amino acid replacement (D189A) switches thrombin specificity from trypsin-like to chymotrypsin-like, converting the substrate preference from H-D-Phe-Pro-Arg-p-nitroanilide to H-D-Phe-Pro-Phe-p-nitroanilide and preferential stability enhancement from PPACK to PPPCK. The observation that thrombin specificity is controlled mainly by a single residue establishes a new paradigm in the field of trypsin-like proteases. Replacement of a single residue changes the primary specificity of thrombin.,Dei Rossi A, Deavila S, Mohammed BM, Korolev S, Di Cera E J Thromb Haemost. 2025 Jan 3:S1538-7836(24)00773-6. doi: , 10.1016/j.jtha.2024.12.024. PMID:39756655[16] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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