Patent Publication Number: US-2023151079-A1

Title: Recombinant protein and fragments thereof, method for producing said recombinant protein, synthetic gene and use of sculptin or recombinant protein for preparing a medicament or pharmaceutical composition for the prophylaxis and/or treatment of thromboembolic diseases or as a direct and specific inhibitor of thrombin

Description:
FIELD OF THE INVENTION 
     The present invention describes a new class of inhibitor proteins of thrombin, particularly direct inhibitors of thrombin, as well as fragments and recombinant protein thereof which can be used as anticoagulant agents. The present invention is within the fields of biochemistry, molecular biology, genetics, pharmacy, medicinal chemistry, being related to Biochemical and Metabolic processes. 
     BACKGROUND OF THE INVENTION 
     Thrombin is a multifunctional enzyme with main function in the coagulation cascade. Its functional modulation may result in normal blood coagulation or in disorders, such as thrombosis. Therefore, the identification of novel strong and specific inhibitors of thrombin is of great importance. 
     Blood coagulation is a dynamic process involving a pro-enzymes cascade leading to a downstream activation of enzymes. In normal conditions, it results in homeostasis. Thrombo-hemorrhagic balance is crucially maintained in the body through a complex and contentious mechanism. However, the disorder thereof may likely result in hemorrhage or thrombosis. Thrombin, a 37 kDa heterodimer, is a central enzyme in the coagulation cascade. Thrombin is a multifunction enzyme acting as a procoagulant through fibrinogen cleavage, which activates coagulation factors (V, VIII, XI, and XIII) and induces platelet aggregation. By the other hand, thrombin may act as an anticoagulant through thrombomodulin binding and activates protein C. In addition, it plays a vital role in arterial and venous thrombosis, disseminated intravascular coagulation (DIC), cancer, inflammatory brain diseases, wound healing and atherosclerosis. In order to overcome its harmful effects, thrombin may be inhibited directly or indirectly by blockage of one or two of its three domains, i.e., active site and exosite 1 and 2. Traditionally, unfractionated heparin (UFH) and low molecular weight heparin (LMWH) have been used as anticoagulants for inhibiting thrombin indirectly by linking simultaneously to anti-thrombin and exosite 2 of thrombin. However, heparin (UFH and LMWH) yields a fibrin-thrombin bridge and increases thrombus formation, and may cause heparin-induced thrombocytopenia. Direct thrombin inhibitors (DTIs) are a group of anticoagulants not requiring a co-factor, which are directly bound to active site of thrombin and block its activity. DTIs have an advantage over indirect inhibitors, because DTIs are more predictable anticoagulants, since they have not antiplatelet effect and they do not result in immune-mediated thrombocytopenia. Several DTIs, including recombinant hirudin and hirulogs thereof, are approved for use as anticoagulants. Hirudin, a 65 amino acid peptide (7 kDa), is a direct thrombin inhibitor which was, firstly, isolated from saliva of medicinal leech  Hirudo medicinalis . Next, a recombinant hirudin form was produced, differing from native hirudin due to the Tyr residue, which is not sulfated. Such difference slightly decreased the recombinant hirudin activity. However, thrombin inhibition through recombinant hirudin is irreversible and generates anti-hirudin antibodies, resulting in drug accumulation. Currently, there is no antidote for reversing recombinant hirudin consequences. In addition, several synthetic hirulogs were developed and tested regarding its inhibitor activity for thrombin, but these inhibitors were almost 800 timer weaker than recombinant hirudin. Among all hirulogs, bivalirudin is a FDA-approved anticoagulant, being a direct thrombin-inhibitor, but presenting short half-life. Almost all of such anticoagulants are related to side effects, like irreversible formation of hirudin-thrombin complex, short half-life of hirulogs, and their dosage should be closely monitored. The most of such thrombin inhibitors are from leeches and are extensively investigated. On the other hand, thrombin-specific inhibitors from ticks were totally forgotten, though Kunitz-type inhibitors had been investigated in detail. 
     Due to those facts, it is interesting the development of a novel class of direct thrombin inhibitors, as well as fragments thereof and recombinant protein, which can be used as anticoagulant agents. 
     In search of the state of the art in scientific and patent literature, the following documents approaching this theme were found:
     1. Posma, J. J. N., Posthuma, J. J. &amp; Spronk, H. M. H. Coagulation and non-coagulation effects of thrombin.  J. Thromb. Haemost.  14, 1908-1916 (2016).   2. Lee, C. J. &amp; Ansell, J. AND. Direct thrombin inhibitors: Parenteral and oral inhibitors of thrombin activity.  Br. J. Clin. Pharmacol.  72, 581-592 (2011).   3. Crawley, J. T. B., Zanardelli, S., Chion, C. K. N. K. &amp; Lane, D. A. The central role of thrombin in hemostasis: Central role of thrombin in hemostasis.  J. Thromb. Haemost.  5, 95-101 (2007).   4. Siller-Matula, J. M., Schwameis, M., Blann, A., Mannhalter, C. &amp; Jilma, B. Thrombin as a multi-functional enzyme: Focus on in vitro and in vivo effects.  Thromb. Haemost.  106, 1020-1033 (2011).   5. Coppens, M., Eikelboom, J. W., Gustafsson, D., Weitz, J. I. &amp; Hirsh, J. Translational Success Stories: Development of Direct Thrombin Inhibitors.  Circ. Res.  111, 920-929 (2012).   6. Weitz, J. I., Hudoba, M., Massel, D., Maraganore, J. &amp; Hirsh, J. Clot-bound thrombin is protected from inhibition by heparin-antithrombin III but is susceptible to inactivation by antithrombin III-independent inhibitors.  J. Clin. Invest.  86, 385-391 (1990).   7. Nasief, N. N., Said, A. M. &amp; Hangauer, D. Modulating hydrogen-bond basicity within the context of protein-ligand binding: A case study with thrombin inhibitors that reveals a dominating role for desolvation.  Eur. J. Med. Chem.  125, 975-991 (2017).   8. Song, X. et al. The NMR solution structure of recombinant RGD-hirudin.  Biochem. Biophys. Res. Commun.  360, 103-108 (2007).   9. Tulinsky, A. Molecular Interactions of Thrombin.  Semin. Thromb. Hemost.  22, 117-124 (1996).   10. Weitz, J. I., Leslie, B. &amp; Hudoba, M. Thrombin Binds to Soluble Fibrin Degradation Products Where it Is Protected From Inhibition by Heparin-Antithrombin but Susceptible to Inactivation by Antithrombin-Independent Inhibitors.  Circulation  97, 544-552 (1998).   11. Dodt, J., Köhler, S. &amp; Baici, A. Interaction of site specific hirudin variants with α-thrombin.  FEBS Lett.  229, 87-90 (1988).   12. Zavyalova, A N D. &amp; Kopylov, A. Multiple inhibitory kinetics reveal an allosteric interplay among thrombin functional sites.  Thromb. Res.  135, 212-216 (2015).   13. Maraganore, J. M., Bourdon, P., Jablonski, J., Ramachandran, K. L. &amp; Fenton, J. W. Design and characterization of hirulogs: a novel class of bivalent peptide inhibitors of thrombin.  Biochemistry  ( Mosc .) 29, 7095-7101 (1990).   14. Branco, V. G. et al. Amblyomin-X having a Kunitz-type homologous domain, is a noncompeting inhibitor of FXa and induces anticoagulation in vitro and in vivo.  Biochim. Biophys. Acta BBA—Proteins Proteomics  1864, 1428-1435 (2016).   15. Macedo-Ribeiro, S. et al. Isolation, Cloning and Structural Characterisation of Boophilin, a Multifunctional Kunitz-Type Proteinase Inhibitor from the Cattle Tick.  PLoS ONE  3, e1624 (2008).   16. Narasimhan, S. et al. Characterization of Ixophilin, A Thrombin Inhibitor from the Gut of  Ixodes scapularis. PLoS ONE  8, e68012 (2013).   17. Liao, M. et al. Hemalin, a thrombin inhibitor isolated from a midgut cDNA library from the hard tick  Haemaphysalis longicornis. J. Insect Physiol.  55, 165-174 (2009).   18. Nava, S. et al. Reassessment of the taxonomic status of  Amblyomma cajennense  ( ) with the description of three new species,  Amblyomma  tonelliae n. sp.,  Amblyomma interandinum  n. sp. and  Amblyomma patinoi  n. sp., and reinstatement of  Amblyomma mixtum , and  Amblyomma sculptum  (Ixodida: Ixodidae).  Ticks Tick - Borne Dis.  5, 252-276 (2014).   19. Batista, I. F. C. et al. Expressed sequence tags (ESTs) from the salivary glands of the tick  Amblyomma cajennense  (Acari: Ixodidae).  Toxicon  51, 823-834 (2008).   20. Kelly, L. M. FLT3 internal tandem duplication mutations associated with human acute myeloid leukemias induce myeloproliferative disease in a murine bone marrow transplant model.  Blood  99, 310-318 (2002).   21. Usón, I. et al. The 1.2 Å crystal structure of hirustasin reveals the intrinsic flexibility of a family of highly disulphide-bridged inhibitors. Structure 7, 55-63 (1999).   22. Tan, S. et al. Efficient expression and secretion of recombinant hirudin III in AND.  coli  using the 1-asparaginase II signal sequence.  Protein Expr. Purif.  25, 430-436 (2002).   23. Kikumoto, R. et al. Selective inhibition of thrombin by (2R,4R)-4-methyl-1-[N2-[1,2,3,4-tetrahydro-8-quinolinyl)sulfonyl]-L-arginyl]-2-piperidinecarboxylic acid.  Biochemistry  ( Mosc .) 23, 85-90 (1984).   24. Tew, D. J. &amp; Bottomley, S. P. Intrinsic fluorescence changes and rapid kinetics of proteinase deformation during serpin inhibition.  FEBS Lett.  494, 30-33 (2001).   25. Witting, J. I., Bourdon, P., Brezniak, D. V., Maraganore, J. M. &amp; Fenton, J. W. Thrombin-specific inhibition by and slow cleavage of hirulog-1 . Biochem. J.  283, 737-743 (1992).   26. Parry, M. A. A., Maraganore, J. M. &amp; Stone, S. R. Kinetic Mechanism for the Interaction of Hirulog with Thrombin.  Biochemistry  ( Mosc .) 33, 14807-14814 (1994).   27. Hsu, H.-J. et al. Factor Xa Active Site Substrate Specificity with Substrate Phage Display and Computational Molecular Modeling.  J. Biol. Chem.  283, 12343-12353 (2008).   28. Borensztajn, K., Peppelenbosch, M. P. &amp; Spek, C. A. Factor Xa: at the crossroads between coagulation and signaling in physiology and disease.  Trends Mol. Med.  14, 429-440 (2008).   29. Borensztajn, K. S. et al. Coagulation factor Xa drives tumor cells into apoptosis through BH3-only protein Bim up-regulation.  Exp. Cell Res.  313, 2622-2633 (2007).   30. Borensztajn, K., Peppelenbosch, M. P. &amp; Spek, C. A. Coagulation Factor Xa inhibits cancer cell migration via LIMK1-mediated cofilin inactivation.  Thromb. Res.  125, e323-e328 (2010).   31. Gleeson, A N D. M. et al. Activated factor X signaling via protease-activated receptor 2 suppresses pro-inflammatory cytokine production from lipopolysaccharide-stimulated myeloid cells.  Haematologica  99, 185-193 (2014).   32. Sierko, A N D. et al. Co-localization of Protein Z, Protein Z-Dependent protease inhibitor and coagulation factor X in human colon cancer tissue: Implications for coagulation regulation on tumor cells.  Thromb. Res.  129, e112-e118 (2012).   33. Drozdetskiy, A., Cole, C., Procter, J. &amp; Barton, G. J. JPred4: a protein secondary structure prediction server.  Nucleic Acids Res.  43, W389-W394 (2015).   34. Kumar, S., Stecher, G. &amp; Tamura, K. MEGA7: Molecular Evolutionary Genetics Analysis Version 7.0 for Bigger Datasets.  Mol. Biol. Evol.  33, 1870-1874 (2016).   35. Asif, H. et al. The chloroplast genome sequence of  Syzygium cumini  (L.) and its relationship with other angiosperms.  Tree Genet. Genomes  9, 867-877 (2013).   36. Iqbal, A. &amp; Azim, M. K. Molecular characterization of hemolysin gene from a Pakistani clinical isolate of  Vibrio cholerae. J. Chem. Soc. Pak.  33, 935-938 (2011).   37. Martins-Pinheiro, M., Lima, W. C., Asif, H., Oller, C. A. &amp; Menck, C. F. M. Evolutionary and Functional Relationships of the dha Regulon by Genomic Context Analysis.  PLOS ONE  11, e0150772 (2016).   38. Francischetti, I. M. B., Valenzuela, J. G. &amp; Ribeiro, J. M. C. Anophelin: Kinetics and Mechanism of Thrombin Inhibition.  Biochemistry  ( Mosc .) 38, 16678-16685 (1999).   39. Iqbal, A., Azim, M. K., Hashmi, N., Ali, S. A. &amp; Musharaf, S. G. Structural characterization of metalloprotease vibriolysin of cholera pathogen  Vibrio cholerae. Protein Pept. Lett.  18, 287-294 (2011).   40. S̆ali, A. &amp; Blundell, T. L. Comparative Protein Modelling by Satisfaction of Spatial Restraints.  J. Mol. Biol.  234, 779-815 (1993).   41. Iqbal, A. &amp; Azim, M. K. Structural Bioinformatics of Enol Pyruvyl Shikimate Phosphate Synthase from  Vibrio cholerae. J. Chem. Soc. Pak.  34, 120-126 (2012).   42. Tao, C., Jin, X., Zhu, L. &amp; Li, H. Two-Dimensional Gel Electrophoresis-Based Proteomic Analysis Reveals N-terminal Truncation of the Hsc70 Protein in Cotton Fibers In vivo.  Sci. Rep.  6, 36961 (2016).   43. Stone, S. R. &amp; Hofsteenge, J. Kinetics of the inhibition of thrombin by hirudin.  Biochemistry  ( Mosc .) 25, 4622-4628 (1986).   

     Therefore, from what is inferred from the searched literature, there are no documents anticipating or suggesting the teachings from the present invention, such that the solution proposed herein has novelty and inventive activity against the state of the art. 
     The solution proposed herein solves the problem of absence of alternative ways to overcome the limitations from antithrombotic therapies or for the treatment or prophylaxis of thromboembolic diseases. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention has the object to solve the problems present in the state of the art as from the development of novel proteins with antithrombotic proprieties or for the treatment or prophylaxis of thromboembolic diseases and/or fragments thereof, acting in direct and specific inhibition of thrombin. 
     Nucleotide sequence used in expression vector is not the same as the sequence naturally found. Amino acid sequence has been identified by analyzing the library of cDNA of tick salivary gland, however codon optimization, addition of restriction sites and histidine tail were performed for purifying the nucleotide sequence used in expression vector, which enabled the development of the process for obtaining the recombinant protein (modification of sculptin originally present in tick salivary gland) on a large scale, using bacteria  E. coli , and exclusively such recombinant protein was used in all studies. 
     Such obtained molecule inhibited selectively thrombin in a competing way. It was slowly cleaved by thrombin and factor Xa. Based on mass spectrometry and Edman analysis, the binding peptide of thrombin active site was proposed, having only few conserved residues compared to classic hirudin from medicinal leech, but it presents the same strength. Gathered data led to conclude that such molecule has the potential to become an anti-thrombotic drug and may potentially compete with classic hirudin and analogues thereof. 
     The present invention has the first object a recombinant protein comprising one sequence with at least 60% of identity with SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16 or combinations of the same. Being SEQ ID NO:1 related to recombinant protein, while SEQ ID NO: 2 to 16 are related to fragments thereof. In one embodiment, recombinant protein comprises one sequence with SEQ ID NO: 1 or SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16 or combinations of the same. 
     The present invention has the second object of a process for obtaining said recombinant protein and/or fragments thereof from salivary gland cDNA from the tick  Amblyomma cajennense.    
     The present invention has the third object of a synthetic gene comprising one sequence with at least 60% of identity with SEQ ID NO: 17. In one embodiment, synthetic gene comprises one sequence with SEQ ID NO: 17. 
     In a fourth object, the present invention presents the use of sculptin or recombinant protein for preparing a medication or pharmaceutical composition for prophylaxis and/or treatment of thromboembolic diseases. 
     In a fifth object, the present invention presents the use of sculptin or recombinant protein for prophylaxis or treatment of thromboembolic diseases or as a Direct and specific inhibitor of thrombin. 
     In a sixth object, the present invention presents an expression vector, gene construct or plasmid comprising the synthetic gene describe in the present invention. 
     In a seventh object, the present invention presents a method of treatment for prophylaxis of thromboembolic diseases comprising administration of an effective dose of sculptin or recombinant protein of the present invention and/or fragments thereof. 
     These and other objects of the invention will be promptly appreciated by those skilled in the art and by companies interesting in such area, and they will be described in sufficient details for reproduction in the following description. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
         FIG.  1    shows phylogenetic analysis of Sculptin. Protein sequences of tick- and leech inhibitors of thrombin were retrieved from database Swiss-Prot/TrEMBL (www.uniprot.org) and the phylogenetic profile was determined using the Neighbor-Joining method embedded in MEGA 7.0. Bootstrap consensus was 100 and the threshold value for condensed tree was 60% replication of corrupted bootstrap (see, experimental procedures). The access number of each sequence is given and the query position is highlighted in red. A single domain of sculptin was taken into account during the phylogenetic construct. 
         FIG.  2    shows the specificity of recombinant protein for thrombin and its dose dependency, and IC 50  for inhibiting thrombin. (A) Inhibition of serine proteases through recombinant protein. Serine protease (100 pM; thrombin, plasmin, trypsin or factor Xa) was incubated with recombinant protein (1, 100 and 200 nM) in phosphate buffer 50 mM containing NaCl 150 mM and 0.1% of PEG 6000, pH 7.4 for 6 h at 37° C. Following addition of chromogenic substrate corresponding to reaction mixture, hydrolysis thereof was monitored at 405 nm. For factor Xa activity, buffer contained phosphatidylserine and phosphatidylcholine 50 μM. Illustration presented in (A) shows the SDSPAGE of purified recombinant protein (SEQ ID NO: 1), which was used in experiments. (B) Typical curves for hydrolysis of chromogenic substrate S-2238 (15 μM) by thrombin 0.1 nM in absence (trace a) or presence of recombinant protein (trace b, 15 pM; trace c, 30 pM; trace d, 60 pM and trace e, 100 pM) in phosphate buffer 50 mM containing NaCl 150 mM and 0.1% of PEG 6000, pH 7.4 at 37° C. (C) Residual activity of thrombin in presence of increasing concentration of recombinant protein. (D) Dose-response curves for thrombin inhibition by recombinant protein. Percentage of thrombin inhibition was plotted versus the concentration record of recombinant protein. Experimental condition of (C) and (D) is the same as in (B). 
         FIG.  3    shows thrombin inhibition kinetics by recombinant protein. (A) Typical progress curves for hydrolysis of chromogenic substrate S-2238 by thrombin 0.1 nM in absence (trace a) and presence of recombinant protein (trace b, 20 pM; trace c, 40 pM; trace d, 60 pM and trace e, 80 pM) in phosphate buffer 50 mM containing NaCl 150 mM and 0.1% of PEG 6000, pH 7.4 at 37° C. Reactions were started by addition of thrombin to mixture containing recombinant protein and S-2238. (B) Lineweaver-Burk plot for thrombin inhibition by recombinant protein using Eq. (1). Reciprocation of initial speed of thrombin inhibition in absence (trace a) and presence of recombinant protein (trace b, 20 pM; trace c, 40 pM and trace d, 60 pM) in differing substrate concentrations. (C) Perceived Km obtained from (B) was plotted versus respective concentration for obtaining Ki. (D) Nonlinear regression for competing inhibition using Eq. (2). Initial speed of thrombin inhibition in absence (trace a) and presence of recombinant protein (trace b, 20 pM; trace c, 40 pM; trace d, 60 pM and trace e, 80 pM) in differing substrate concentrations. Experimental condition of (B), (C) and (D) is the same as of (A). 
         FIG.  4    shows the relation between apparent first order rate and concentration of tight binding inhibitor of recombinant protein. (A) Typical progress curves for hydrolysis of chromogenic substrate S-2238 15 μM by thrombin 0.1 nM in absence (trace a) and presence of recombinant protein (trace b, 10 pM; trace c, 30 pM; trace d, 70 pM; trace e, 100 pM; trace f, 200 pM and trace g, 500 pM) in phosphate buffer 50 mM containing NaCl 150 mM and 0.1% of PEG 6000, pH 7.4 at 37° C. Reactions were started through thrombin addition to mixture containing recombinant protein and S-2238. (B) Equilibrium rate of thrombin regarding to concentration of recombinant protein (C) Calculation of constant off-rate. Constant of apparent first order rate was calculated using a nonlinear regression adjustment, where crossing and slope are kon and koff respectively. Experimental condition of (B) and (C) is the same of (A). 
         FIG.  5    shows degradation of recombinant protein by serine proteases and its activity of thrombin inhibition. Recombinant protein (10 μM) was incubated with or without serine protease 1 μM (thrombin, plasm in, trypsin or factor Xa) in phosphate buffer 50 mM containing NaCl 150 mM and 0.1% of PEG 6000, pH 7.4 for 4, 6, 7 or 18 h at 37° C. Reaction mixtures (20 μl) were split by SDS-PAGE. (A) hydrolysis SDS-PAGE (15%) of recombinant protein by serine proteases following 6 h of incubation. (B) Percentage of thrombin inhibition by recombinant protein following 6 h of incubation with serine protease (see experimental procedures). (C) hydrolysis SDS-PAGE (15%) of recombinant protein by serine proteases following 18 h of incubation. (D) Percentage of thrombin inhibition by recombinant protein following 18 h of incubation with serine protease (see experimental procedures). Numbering of (B) and (D) corresponds to numbering of (A) and (C), respectively, and recombinant protein control is represented by CTRL. Recombinant protein (strip 1); thrombin (strip 2) and thrombin with recombinant protein (strip 3); plasmin (strip 4) and plasmin with recombinant protein (strip 5); trypsin (strip 6) and trypsin with recombinant protein (strip 7); factor Xa (strip 8) and factor Xa with recombinant protein (strip 9) and protein marker (strip 10; in A). (E) Identification of cleavage sites of thrombin in recombinant protein following 7 h of incubation. (F) Identification of cleavage sites of factor Xa in recombinant protein following 4 h of incubation. Cleavage sites of thrombin and factor Xa in recombinant protein sequence are shown in FIGS. S1 and S2, respectively. Experimental procedure for (C), (D), (E) and (F) was the same as for (A) and (B), except the incubation time and the type of serine protease used. 
         FIG.  6    shows thrombin inhibition activity of recombinant protein fragments generated by factor Xa. Recombinant protein (10 μM) was incubated with or without factor Xa 1 μM in phosphate buffer 50 mM containing NaCl 150 mM, and phosphatidylserine and phosphatidylcholine 50 μM, pH 7.4 for 18 h at 37° C. (A) Reaction mixtures were split through reverse phase HPLC column C-18. (B) Gathered peaks (H1-H5) were subjected to MALDI-TOF MS and thrombin inhibition test (see table 1, for correspondent peptide sequence). (C) Typical progress curves for hydrolysis of chromogenic substrate S-2238 15 μM by thrombin 0.1 nM in absence (trace Ctrl) and presence of recombinant protein fragment 100 pM (traces H1 and H3) or preserved recombinant protein (trace Scpt) in phosphate buffer 50 mM containing NaCl 150 mM and 0.1% of PEG 6000, pH 7.4 at 37° C. (D) Percentage of thrombin inhibition by recombinant protein and fragments thereof. Reaction conditions of percentage of thrombin inhibition were obtained from (C). 
       A  FIG.  7    shows a representative design (Solid strip) of thrombin-linked recombinant protein and hirudin. Brown and cyan colors represent heavy and light chain of thrombin respectively. (A) Recombinant protein in green linked to thrombin (B) Hirudin in blue linked to thrombin. Residue lys from inhibitors is shown in yellow and residue of Ser195 from thrombin active site is shown in red. 
         FIG.  8    shows an analysis of protein sequence. (A) recombinant protein sequence modified from sculptin, in whose transcriptome analysis of tick salivary gland was identified. Assumed peptide signal is underlined. Four peptide iterations within recombinant protein are shown by alternated grey and yellow colors. (B) Multiple alignment of recombinant protein with hirudin from  Amblyomma cajennense, Rhipicephalus appendiculatus  and  Hirudo medicinalis . Conserved residues are highlighted in grey. Hirudin PKP-linked active site from  Hirudo medicinalis  is modified to PKM in sculptin. Cleavage sites of factor Xa and thrombin are identified through asterisk and hash mark, respectively. 
         FIG.  9    shows expression and purification of recombinant protein. Synthetic gene of recombinant protein was cloned into expression vector pET28a and recombinant protein was expressed in  E. coli  BL21 (DE3) in liquid medium at 37° C. Whole cell lysates from both no induced or induced cultures (IPTG 0.5 mM) were analyzed through SDS-PAGE (15%). (A) Induction SDS-PAGE of recombinant protein. Strip M, NI and I represent protein marker, non IPTG induced, respectively. (B) SDS-PAGE of cell lysate from  E. coli  following recombinant protein expression. Strips M, TE, IN, SO correspond to protein marker, full extract, insoluble and soluble fractions, respectively. (C) Purification by affinity chromatography of recombinant protein. Soluble fraction was filtered through a 0.45 μm membrane and applied in Ni chelating affinity column of His tag. Linked protein was eluted with imidazole and 15 μl from each fraction was analyzed from SDS-PAGE. (D) SDS-PAGE from affinity chromatography fractions. Strips TE, E, M and U represent full extract, fractions of eluted protein, protein marker and non-linked protein fraction respectively. (E) Purification of recombinant protein through Ion exchange chromatography. Inserted image showing SDS-PAGE from strip of purified recombinant protein. 
         FIG.  10    shows purification of recombinant protein, a thrombin-specific inhibitor. (A) SDS-PAGE from purified recombinant protein using conventional chromatographic methods (see experimental procedures and FIG. S2). (B) MALDI-TOF MS spectrum from purified recombinant protein. 
         FIG.  11    shows APTT, PT and TT assessment in vitro in isolated human plasma incubated with differing concentrations of recombinant protein. Plasma was obtained from blood of healthy human volunteer and incubated with different concentrations of recombinant protein. APTT, PT and TT were determined like experimental procedure. (A) Activated partial thromboplastin time (B) prothrombin time and (C) thrombin time. Ctrl is related to plasma and Sal is related to plasma plus saline. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Herein, a novel class of thrombin inhibitors will be described, particularly direct and specific thrombin inhibitors, which were modified from sculptin identified in transcriptome analysis of tick salivary glands. It consists in 168 residues having four exactly similar repeats and presenting evolving divergence from classic hirudin. Recombinant protein is a competing, specific, and reversible thrombin inhibitor, with K of 18.5±2.2 pM. It is slowly digested by thrombin and loses its inhibitory activity. Accordingly, recombinant protein is hydrolyzed by factor Xa and each polypeptide fragment is able for inhibiting thrombin in independent way. One single domain of recombinant protein retains solely ˜45% of inhibitory activity, which was proposed for binding to thrombin in bivalent way. Formation of structure similar to helix/small turn by binding residues of active site from domain of recombinant protein may become it a thrombin inhibitor most potent than hirulogs. In addition, recombinant protein prolongs coagulation through its extrinsic and intrinsic metabolic pathways. It was considered along with data to allow for settling that recombinant protein and independent domain(s) thereof have strong potential for becoming a therapeutic antithrombotic compound or for novel treatment of thromboembolic diseases. 
     The present invention has the inventive concept common to several objects thereof the inhibitors of thrombin, particularly direct thrombin inhibitors and fragments thereof. 
     In one first object, the present invention shows a recombinant protein comprising one sequence with at least 60% of identity with SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16 or combinations of the same. In one embodiment, recombinant protein comprises one sequence with at least 70%, more preferentially at least 90%, more preferentially at least 95%, even more preferentially at least 99% of identity with SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16 or combinations of the same. 
     In one embodiment, recombinant protein consists of one sequence with at least 60% of identity with SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16 or combinations of the same. In one embodiment, recombinant protein consists of one sequence with at least 70%, more preferentially at least 90%, more preferentially at least 95%, even more preferentially at least 99% of identity with SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16 or combinations of the same. 
     In one embodiment, recombinant protein comprises one sequence with SEQ ID NO: 1 or SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16 or combinations of the same. 
     In one embodiment, recombinant protein consists of sequence with SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16 or combination of the same. 
     The present invention has as a second object a process for obtaining said recombinant protein and/or fragments thereof from salivary gland cDNA from tick  Amblyomma cajennense.    
     In a third object, the present invention shows a synthetic gene comprising one sequence with at least 60% of identity with SEQ ID NO: 17. In one embodiment, synthetic gene comprises one sequence with at least 70%, more preferentially at least 90%, more preferentially at least 95%, even more preferentially at least 99% of identity with SEQ ID NO: 17. 
     In one embodiment, synthetic gene consists of one sequence with at least 60% of identity with SEQ ID NO: 17. In one embodiment, synthetic gene consists of one sequence with at least 70%, more preferentially at least 90%, more preferentially at least 95%, even more preferentially at least 99% of identity with SEQ ID NO: 17. 
     In one embodiment, synthetic gene comprises one sequence with SEQ ID NO: 17. 
     In one embodiment, synthetic gene consists of one sequence with SEQ ID NO: 17. 
     In a fourth object, the present invention shows the use of sculptin or recombinant protein for preparing a medication or pharmaceutical composition for prophylaxis and/or treatment of thromboembolic diseases. 
     In a fifth object, the present invention shows the use of sculptin or recombinant protein for prophylaxis and/or treatment of thromboembolic diseases and/or as a direct and specific inhibitor of thrombin. 
     In a sixth object, the present invention shows an expression vector, gene construct or plasm id comprising the synthetic gene described in the present invention. 
     In a seventh object, the present invention shows a method for treatment and/or prophylaxis of thromboembolic diseases comprising administration of an effective dose of sculptin or recombinant protein of the present invention and/or fragments thereof. 
     In context of the present invention, “thromboembolic diseases” may be understood as disorders related to coagulation or blockage of blood vessels, arteries or veins by locally formed clots or by thrombus delivered in systemic circulation, such e.g., thrombosis, heart attack, apoplexy, Angina pectoris (including unstable angina), reocclusions and restenosis following angioplasty or coronary artery bypass, peripheral arterial occlusive diseases, transitory ischemic attacks, pulmonary embolisms, deep vein thrombosis, or disseminated intravascular coagulation (DIC). 
     Therefore, the invention contributes for health-related areas, novel thrombin inhibitors are disclosed, particularly direct and specific thrombin inhibitors, highly specified, useful in treatment or prophylaxis of thromboembolic diseases. 
     EXAMPLES—EMBODIMENTS 
     Examples shown herein aim solely exemplify one from several ways to implement the invention, however without limitation of the scope thereof by no means. 
     Amino acid sequence of sculptin was identified from analysis of cDNA library of salivary gland from tick  Amblyomma cajennense  (currently  Amblyomma sculptum ). 
     As from the amino acid sequence identified in library, a reverse translation was performed, through software BLAST-X (NCBI), using table of use of codons from  Escherichia coli , thus, leading to a coding DNA sequence for recombinant protein, for protein expression in heterologous system ( E. coli  BL21(DE3). 
     As from coding nucleotide sequence of sculptin, a synthetic gene was designed (described in SEQ ID NO: 17), incorporating a cleavage site of restriction enzyme Ncol at end 5′ and the coding sequence for histidine tail (HIS6) and a cleavage site of restriction enzyme Xhol at end 3′. Next, synthetic gene sequence was sent to company GenOne Soluçe̋s em Biotecnologia (Rio de Janeiro, Brazil) for codon optimization with a proprietary algorithm, gene synthesis and cloning in expression vector for  E. coli , pET-28a (Novagen, Merck Biosciences, Dramstadt, Germany). 
     Plasmid synthesized and provided by company GenOne was used for transforming strain of  E. coli  One Shot BL21(DE3) (Invitrogen, Carlsbad, Calif., USA) through method with calcium chloride. 
     10 ng of plasmid pET28a-Sculptin was incubated with 50 μL of competing cell suspension BL21(DE3) for 30 minutes in ice. Next, cells were undergone to thermal shock by incubation at 42° C. for 30 minutes, followed by incubation in ice for 10 minutes. Afterwards, 1 mL of LB medium was added and the suspension was incubated for one hour at 37° C. 
     Following the above, cells were plated in solid LB culture medium containing 100 μg/mL of ampicillin and the plate was incubated overnight at 37° C. The next day, a colony was isolated and used for inoculation of LB medium 10 mL containing 100 μg/mL of ampicillin overnight, at 37° C. The next day, glycerol 50% was added to culture, suspension was partitioned in tubes containing 1 mL of suspension and the same were frozen at −80° C., giving rise to master seed lot. 
     Experiments for expression of recombinant protein in  E. coli  were always started from a bottle of seed lot, inoculating in LB medium containing 100 μg/mL of ampicillin and maintained at 37° C. with stirring of 240 rpm overnight, which composes pre-inoculums. 
     The next day, a sufficient amount of pre-inoculums was used for inoculating LB culture medium containing 100 μg/mL of ampicillin, in a ratio of 1 volume of pre-inoculums to 100 volumes of culture medium. Culture was maintained at 37° C., with stirring at 240 rpm, during about two hours, up to achieve optic density (0D600) between 0.5-0.6. When such optic density was achieved, IPTG inductor was added in a final concentration of 1 mM, and culture was incubated again at 37° C. for 4 hours. 
     Following incubation, cells were harvested through centrifugation at 6000 rpm for 30 minutes, and supernatant was discarded when centrifugation ends. Cells were re-suspended in saline solution NaCl (150 mM) in a ratio of 1 mL of solution to every 8 g of wet cell mass (from this step forward the ratio of 1 mL of iced solution for every 8 g of wet mass was used in all processes). Cells were centrifuged again as above and re-suspended in lysis buffer. Lysozyme was added to suspension in a final concentration of 0.25 mg/mL for every cell wall disruption, and incubation was maintained for 30 minutes at 37° C. with stirring at 80 rpm. Next, suspension was undergone to 4 sonication cycles in strength of 70% for cell disruption and fragmentation of genomic DNA. 
     Suspension was centrifuged at 16000 rpm (4° C.) for one hour in order to split insoluble material from soluble material. 
     Recombinant protein (SEQ ID NO: 1) was expressed in bacterium cytoplasm, thus, soluble fraction was used for purifying protein, which contains histidine tail through affinity chromatography, using chromatography system AKTA AVANT (GE Healthcare, Chicago, Ill., USA) and column HisTrap FF. Soluble material was applied in column, thus immobilizing the recombinant protein. Following, washing was performed with 10 CV (column volumes) of lysis buffer. Protein elution was performed through linear gradient (10 CV) from zero to 100% of buffer B. Harvested fractions containing partially purified protein were undergone to buffer exchange in desalting column (HiPrep 26/10) and one second purification step of recombinant protein was performed through ion exchange chromatography in column CaptoQ, using the same washing and elution steps through linear gradient described above. Fractions containing the purified protein were combined in a pool and buffer exchange to PBS buffer was performed through desalting column (HiPrep 26/10). 
     Recombinant protein (SEQ ID NO: 1) in pure form obtained through such process was used in all experiments described herein. 
     Analysis of Sculptin Sequence and Phylogeny 
     Sculptin sequence was identified in transcriptome profile from salivary glands of  Amblyomma cajennense . Sculptin, a 168 amino acid polypeptide consists of one single peptide, and four exactly similar repeats of 34 amino acids ( FIG.  8 A ). Multiple alignment of classic hirudin from medicinal leech presented only few similarities and even residues linked to thrombin active site were not preserved. The phylogenetic analysis from a domain of single sculptin repeat to other serine protease inhibitors suggested that it shares a common predecessor with variants of leech hirudin, but it is different regarding evolving time. In fact, in evolving tree, sculptin was closer to serine protease inhibitors from antistassin family, i.e., hirustasin, guamerin, bdellastasin, theromin and therostasin, than classic hirudin from leech. As expected, sculptin belongs to the same sequence family similar to those from tick hirudin ( FIG.  1   ). 
     Purification of Recombinant Protein 
     Synthetic construct of recombinant protein without signal peptide and with one polyhistidine tail C-terminal was cloned into expression vector pET28a. Recombinant protein was well expressed and was present mainly in soluble fraction ( FIG.  9   ). Recombinant protein was purified by conventional affinity and ion exchange chromatography ( FIG.  9   ). Analysis by mass spectrometry indicated a mass of 16990.90 Da for recombinant protein (SEQ ID NO: 1) in purified form, however in SDS-PAGE, it is performed just above the marker strip of 20 kDa ( FIGS.  10 A and  10 B ). Purified recombinant protein was used for additional experiments (image inserted in  FIG.  2 A ). 
     Recombinant Protein is a Thrombin-Specific Inhibitor 
     The first performed experiment was the test of serine proteases inhibition through recombinant protein. For this purpose, thrombin, trypsin, plasm in and factor Xa were chosen. Hydrolysis of a chromogenic substrate through serine proteases in the presence and absence of recombinant protein was monitored in a spectrophotometer way. Recombinant protein in concentration of 1 nM decreases the residual activity of thrombin in about 97% ( FIG.  2 A ). For the other hand, recombinant protein (1, 100, 200 nM) did not inhibit factor Xa, trypsin and plasmin ( FIG.  2 A ). 
     Inhibition of Thrombin Residual Activity by Recombinant Protein and Calculation of IC 50  Value 
     Thrombin was the sole enzyme inhibited by recombinant protein. Additionally, thrombin inhibition was analyzed with increasing concentrations of recombinant protein. Data rendered that the increase of a concentration of recombinant protein decreased residual activity of thrombin ( FIG.  2 B-D ). Percentage plot of inhibition versus concentration log was adjusted in dose-response function of equation 1 and IC 50  value of 86.6±1.9 pM was calculated ( FIG.  3 D ). 
     Kinetics Thrombin Inhibition by Recombinant Protein 
     In order to assess the inhibition type performed by recombinant protein in thrombin, kinetics parameters of chromogenic substrate S-2238 hydrolysis by thrombin in presence of recombinant protein were determined. For this purpose, several tests were performed using (i) a fixed substrate concentration and increasing concentrations of recombinant protein; and (ii) a fixed concentration of recombinant protein and increasing concentrations of S-2238. Typical hydrolysis curves of S-2238 by thrombin are given in  FIG.  3 A . Initial speed of chromogenic substrate S-2238 hydrolysis by thrombin in presence of recombinant protein was adjusted to Lineweaver-Burk plots using equation 2. Lineweaver-Burk plots suggest a constant Vmax and changes in Km compared to reaction in absence of recombinant protein, which is a characteristic of competing inhibition ( FIG.  3 B ). Apparent Km for each inhibitor concentration was plotted versus respective inhibitor concentration and Ki was calculated using equation 3. Ki value obtained was 18.5±2.2 pM of recombinant protein for thrombin inhibition ( FIG.  3 C ) and it was even confirmed by data adjustment to nonlinear regression for competing enzyme inhibition using equations 3 and 4 ( FIG.  3 D ). Ki value of 18.1±1.7 pM obtained through this method was similar to that calculated previously ( FIG.  4 D ). 
     Binding Kinetics of Recombinant Protein to Thrombin 
     For binding kinetics, pre-mixed substrate and recombinant protein concentrations were added to reaction mixtures already containing thrombin (see experimental procedure). Traces of inhibition are straight and separate lines right from the beginning of reaction, thus suggesting fast and tight binding between recombinant protein to thrombin ( FIG.  4 A ). In addition, fractional speeds were plotted versus inhibitor concentrations using equation 5 of Morrison tight binding and data is best suited in equation ( FIG.  4 B ). Ki of 19.5±3.5 pM was calculated by equation of Morrison tight binding, which was similar to that determined by nonlinear regression for competing enzyme inhibition. Further, k obs  calculated using equation 6 was plotted versus recombinant protein concentration. From the plot, k on  and k off  were calculated which resulted in 4.04±0.03×10 7  M −1  s −1  and 0.65±0.04×10 −3  s −1  respectively ( FIG.  4 C ). Inhibition constant (Ki) of 16.1±1.4 pM was calculated using equation 7. 
     Degradation of Recombinant Protein by Serine Proteases 
     Afterwards, it was determined whether serine proteases, like thrombin, plasmin, factor Xa and trypsin, hydrolyze recombinant protein. For this purpose, recombinant protein (10 μM) was incubated with or without serine protease 1 μM (thrombin, plasmin, trypsin or factor Xa) in phosphate buffer 50 mM containing NaCl 150 mM and 0.1% of PEG, pH 7.4 for 6 h or 18 h at 37° C. SDS-PAGE of reaction mixture following 6 h of incubation presented that, compared to control strip of recombinant protein, strip intensity of 20-kDa (corresponding to non-digested recombinant protein) decreased and strips of lower molecular weight appeared in recombinant protein incubated by thrombin ( FIG.  5 A ). For the other hand, following 6 h of incubation, strip of 20-kDa completely disappeared in recombinant protein incubated by plasm in and trypsin ( FIG.  5 A ). Accordingly, following the same incubation time, factor Xa also converted the recombinant protein in fragments ( FIG.  5 A ). For the test of thrombin inhibition, the same samples were diluted 100 thousand times for a final concentration of recombinant protein of 100 pM and reaction mixtures were further supplemented with thrombin 100 pM. Upon addition of chromogenic substrate S-2238, the hydrolysis thereof by thrombin was monitored in spectrophotometer way. Data reveal that recombinant protein incubated without serine protease for 6 h inhibited thrombin in similar way to control (control is 100 pM of fresh recombinant protein;  FIG.  5 B ). For the other hand, recombinant protein incubated with thrombin presented its inhibitory activity decreased by 20% and recombinant protein incubated for 6 h with plasmin or trypsin presented its inhibitory activity decreased by 80% ( FIG.  5 B ). Interestingly, recombinant protein digested with factor Xa retained its thrombin inhibition activity ( FIG.  5 B ). Afterwards, recombinant protein incubated with serine proteases for 18 h was examined. Strip of 20-kDa, corresponding to recombinant protein monomer, completely disappeared from reaction mixtures of recombinant protein incubated with serine protease ( FIG.  5 C ). In the same way, for test of thrombin inhibition, samples were diluted 100 thousand times and they were further supplemented with thrombin 100 pM. As expected, recombinant protein incubated without serine protease for 18 h inhibited thrombin in similar way to control of fresh recombinant protein ( FIG.  5 D ). However, recombinant protein incubated with thrombin, plasmin and trypsin did not inhibit thrombin ( FIG.  5 D ). Interestingly, recombinant protein incubated by factor Xa even inhibited the thrombin activity ( FIG.  5 D ). 
     Sequencing N-Terminal of Recombinant Protein Hydrolyzed by Thrombin 
     As discussed above, thrombin degrades recombinant protein. Hereinafter, our next step was to determine cleavage sites of thrombin in recombinant protein sequence. For this purpose, recombinant protein was incubated with thrombin for 7 h and peptides generated during hydrolysis were split by reverse phase chromatography. Individual peaks were gathered and undergone to Edman N-terminal sequencing. Sequenced residues for the first peak were GKPQG, being the first five residues of recombinant protein ( FIG.  5 E ). Sequenced residues for the following three peaks (2 nd  3 rd  and 4 th ) were MPKGG, being basically N-terminal residues of recombinant protein peptides generated by thrombin ( FIG.  5 E ). The last peak (5th) with a retention time equal to control was sequenced for having residues of MPKGG and GKPQG in N-terminal, suggesting that this peak has preserved and partially degraded recombinant protein ( FIG.  5 E ). Fractions were also undergone to mass spectrometry, and they were in accordance with data from Edman sequencing (Table 1). Theoretical and experimental masses of peptides are listed on table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Recombinant protein fragments generated by thrombin. 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Theoretical 
                 Calculated 
               
               
                 Peak 
                   
                 Mass 
                 Mass c   
               
               
                 number a   
                 Recombinant protein fragment  b   
                 [MH]+ 
                 [MH]+ 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 H1 
                   GKPQG HPHDALEARSDAVHTAVPK (SEQ 
                 2518.77 
                 2521.74 
               
               
                   
                 ID NO: 2) 
                   
                   
               
               
                   
                 GKPQGHPHDALEARSDAVHTAVPKMPK 
                 6162.85 
                 6169.56 
               
               
                   
                 GGHGGFEPIPIDYDERALEARSDAVHTAV 
                   
                   
               
               
                   
                 PK (SEQ ID NO: 3) 
                   
                   
               
               
                   
               
               
                 H2 
                   MPKGG HGGFEPIPIDYDERALEARSDAVH 
                 3663.09 
                 3663.90 
               
               
                   
                 TAVPK (SEQ ID NO: 4) 
                   
                   
               
               
                   
               
               
                 H3 
                   MPKGG HGGFEPIPIDYDERALHALEHHHH 
                 3572.92 
                 3572.70 
               
               
                   
                 HH (SEQ ID NO: 5) 
                   
                   
               
               
                   
               
               
                 H5 
                   MPKGG HGGFEPIPIDYDERALEARSDAVH 
                 7217.00 
                 7202.66 
               
               
                   
                 TAVPKMPKGGHGGFEPIPIDYDERALHAL 
                   
                   
               
               
                   
                 EHHHHHH (SEQ ID NO: 6) 
                   
                   
               
               
                   
               
               
                 H6 
                   MPKGG HGGFEPIPIDYDERALEARSDAVH 
                 7282.19 
                 7261.19 
               
               
                   
                 TAVPKMPKGGLGGFEPIPIDYDERALEAR 
                   
                   
               
               
                   
                 SDAVHTAVPK (SEQ ID NO: 7) 
                   
                   
               
               
                   
               
               
                   
                   MPKGG LGGFEPIPIDYDERALEARSDAVH 
                 10837.10 
                 10807.97 
               
               
                   
                 TAVPKMPKGGHGGFEPIPIDYDERALEAR 
                   
                   
               
               
                   
                 SDAVHTAVPKMPKGGHGGFEPIPIDYDER 
                   
                   
               
               
                   
                 ALHALEHHHHHH (SEQ ID NO: 8) 
                   
                   
               
               
                   
               
               
                   
                   MPKGG HGGFEPIPIDYDERALEARSDAVH 
                 14481.18 
                 14431.37 
               
               
                   
                 TAVPKMPKGGLGGFEPIPIDYDERALEAR 
                   
                   
               
               
                   
                 SDAVHTAVPKMPKGGHGGFEPIPIDYDER 
                   
                   
               
               
                   
                 ALEARSDAVHTAVPKMPKGGHGGFEPIPI 
                   
                   
               
               
                   
                 DYDERALHALEHHHHHH (SEQ ID NO: 9) 
                   
                   
               
               
                   
               
               
                   
                   GKPQG HPHDALEARSDAVHTAVPKMPK 
                 16981.94 
                 16990.90 
               
               
                   
                 GGHGGFEPIPIDYDERALEARSDAVHTAV 
                   
                   
               
               
                   
                 PKMPKGGLGGFEPIPIDYDERALEARSDA 
                   
                   
               
               
                   
                 VHTAVPKMPKGGHGGFEPIPIDYDERALE 
                   
                   
               
               
                   
                 ARSDAVHTAVPKMPKGGHGGFEPIPIDYD 
                   
                   
               
               
                   
                 ERALHALEHHHHHH (SEQ ID NO: 1) 
               
               
                   
               
            
           
         
       
     
     Recombinant protein (10 μM) was incubated with thrombin 1 μM in phosphate buffer 50 mM containing NaCl 150 mM and 0.1% of PEG 6000 pH 7.4 for 4 h at 37° C. Reaction mixtures were split by reverse phase HPLC column C-18. Fractions were undergone to Edman sequencing or mass spectrometry MALDI-TOF. 
     Sequencing of N-Terminal of Recombinant Protein Hydrolyzed by Factor Xa 
     Cleavage sites of factor Xa in recombinant protein were also determined. Peptides generated by incubation of recombinant protein with factor Xa for 4 h were split by reverse phase chromatography. Edman sequencing presented that N-terminal residues for the first peak were GKPQG, being the first five residues of recombinant protein ( FIG.  5 F ). Sequenced residues for the next two peaks (2 nd  and 3 rd ) were SDAVH, which are in fact N-terminal residues of recombinant protein peptides generated by factor Xa ( FIG.  5 F ). The last peak (4 th ) with retention time equal to control was sequenced to have N-terminal residues MPKGG and SDAVH, suggesting that this peak has preserved and partially degraded recombinant protein ( FIG.  5 F ). Next, gathered peaks were undergone to mass spectrometry, which were in accordance with data from Edman sequencing (Table 2). Theoretical and experimental masses of peptides are listed on table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Recombinant protein fragments 
               
               
                 generated by factor Xa. 
               
            
           
           
               
               
               
               
            
               
                 Peak 
                 Recombinant protein 
                 Theo- 
                   
               
               
                   
                   
                 reti- 
                 Calcu- 
               
               
                   
                   
                 cal 
                 lated 
               
               
                 number 
                 fragmentation 
                 Mass 
                 Mass 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 H1 
                   GKPQG HPHDALEARSDAVHTAVPKM 
                 5156.74 
                 5153.57 
               
               
                   
                 PKGGHGGFEPIPIDYDERALEAR 
                   
                   
               
               
                   
                 (SEQ ID NO: 10) 
                   
                   
               
               
                   
               
               
                 H2 
                   SDAVH TAVPKMPKGGHGGFEPIPIDY 
                 3663.10 
                 3667.50 
               
               
                   
                 DERALEAR (SEQ ID NO: 11) 
                   
                   
               
               
                   
               
               
                   
                   SDAVH TAVPKMPKGGHGGFEPIPIDY 
                 4579.05 
                 4582.40 
               
               
                   
                 DERALHALEHHHHHH 
                   
                   
               
               
                   
                 (SEQ ID NO: 12) 
                   
                   
               
               
                   
               
               
                 H3 
                   SDAVH TAVPKMPKGGHGGFEPIPIDY 
                 8223.13 
                 8220.55 
               
               
                   
                 DERALEARSDAVHTAVPKMPKGGHG 
                   
                   
               
               
                   
                 GFEPIPIDYDERALHALEHHHHHH 
                   
                   
               
               
                   
                 (SEQ ID NO: 13) 
                   
                   
               
               
                   
               
               
                   
                   SDAVH TAVPKMPKGGHGGFEPIPIDY 
                 6765.55 
                 6770.60 
               
               
                   
                 DERALEARSDAVHTAVPKMPKGGHG 
                   
                   
               
               
                   
                 GFEPIPIDYDER 
                   
                   
               
               
                   
                 (SEQ ID NO: 14) 
                   
                   
               
               
                   
               
               
                 H4 
                   SDAVH TAVPKMPKGGHGGFEPIPIDY 
                 7306.17 
                 7299.61 
               
               
                   
                 DERALEARSDAVHTAVPKMPKGGHG 
                   
                   
               
               
                   
                 GFEPIPIDYDERALEAR 
                   
                   
               
               
                   
                 (SEQ ID NO: 15) 
                   
                   
               
               
                   
               
               
                   
                   GKPQG HPHDALEARSDAVHTAVPKM 
                 12420.90 
                 12427.54 
               
               
                   
                 PKGGHGGFEPIPIDYDERALEARSD 
                   
                   
               
               
                   
                 AVHTAVPKMPKGGLGGFEPIPIDYD 
                   
                   
               
               
                   
                 ERALEARSDAVHTAVPKMPKGGHGG 
                   
                   
               
               
                   
                 FEPIPIDYDERALEAR 
                   
                   
               
               
                   
                 (SEQ ID NO: 16) 
                   
                   
               
               
                   
               
               
                   
                   GKPQG HPHDALEARSDAVHTAVPKM 
                 16981.94 
                 16990.90 
               
               
                   
                 PKGGHGGFEPIPIDYDERALEARSD 
                   
                   
               
               
                   
                 AVHTAVPKMPKGGLGGFEPIPIDYD 
                   
                   
               
               
                   
                 ERALEARSDAVHTAVPKMPKGGHGG 
                   
                   
               
               
                   
                 FEPIPIDYDERALEARSDAVHTAVP 
                   
                   
               
               
                   
                 KMPKGGHGGFEPIPIDYDERALHAL 
                   
                   
               
               
                   
                 EHHHHHH 
                   
                   
               
               
                   
                 (SEQ ID NO: 1) 
               
               
                   
               
            
           
         
       
     
     Recombinant protein (10 μM) was incubated with factor Xa 1 μM in phosphate buffer 50 mM containing NaCl 150 mM and 50 μM de PS/PC pH 7.4 for 4 h at 37° C. Reaction mixtures were split by reverse phase HPLC column C-18. Fractions were undergone to Edman sequencing or mass spectrometry MALDI-TOF. 
     Recombinant Protein Fragments Generated by Factor Xa Retain Thrombin Inhibition Activity 
     In addition, recombinant protein was incubated with factor Xa for 18 h and resulting peptides were split by reverse phase chromatography ( FIG.  6 A ). Peaks (named as H1, H2, H3 H4 and H5) were gathered and undergone to mass spectrometry MALDI-TOF ( FIG.  6 B ). In accordance with analysis of mass spectrometry, H1 corresponds to average mass of 5153.57 Da, H2 corresponds to average mass of 3667.50 Da and 4582.40 Da and H3 corresponds to average mass of 8220.55 Da and 6770.60 Da. Similarly, H4 corresponds to average mass of 7299.61 Da and 12427.54 Da and H5 corresponds to 16990.90, 12427.54 Da and 11843.17 Da ( FIG.  6 B , Table 1). Further, fractions (H1, H2, H3 and H4) were undergone to test of thrombin inhibition ( FIG.  6 C ). Fractions H1, H2, H3 and H4 retained thrombin inhibition activity of about 50%, 45%, 70% and 80% respectively, of preserved no hydrolyzed recombinant protein ( FIG.  6 D ). Peak H5 had mainly preserved recombinant protein, thus it was not considered for test of thrombin inhibition. 
     The Effect of Recombinant Protein in aPTT, PT and TT 
     Finally, PT, aPTT and TT were assessed in isolated plasma of healthy human volunteers following incubation with recombinant protein for 3 min. at 37° C. Data shows that aPTT and PT were prolonged by recombinant protein in concentration-dependent way ( FIGS.  11 A and  11 B ). Maximum test reading for aPTT was achieved following 12 nM, while for PT that was achieved following 6 nM of recombinant protein ( FIGS.  11 A and  11 B ). For the other hand, TT was prolonged by recombinant protein in peak-molar range ( FIG.  11 C ). 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Comparison of biochemical proprieties of thrombin inhibitors. 
               
            
           
           
               
               
               
               
               
               
            
               
                 Inhibitor a   
                 Inhibition Type 
                 K i  Value 
                 Administration 
                 Half-life b   
                 Ref. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Recombinant 
                 Competing 
                 19 ± 2  
                 pM 
                 Intravenously 
                 1.3  
                 h 
                 [ 11,12 ] 
               
               
                 Hirudin d   
                   
                   
                   
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Sulfo-hirudin d   
                 Competing 
                 1.2 ± 0.2  
                 pM 
                 ND 
                 ND 
                 [ 26,43 ] 
               
               
                 Hirugen d   
                 No competing 
                 1.3 ± 0.2  
                 μM 
                 ND 
                 ND 
                 [ 24 ] 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Bivalirudin d   
                 No competing 
                 1.9 ± 2.6  
                 nM 
                 Intravenously 
                 25  
                 min 
                 [ 13,25,26 ] 
               
               
                 Argatroban 
                 No competing 
                 39 ± 2  
                 nM 
                 Intravenously 
                 50  
                 min 
                 [ 23 ] 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Recombinant 
                 Competing 
                 18.5 ± 2.2 
                 pM 
                 ND 
                 ND 
                 This 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 protein 
                   
                   
                   
                   
                 8  
                 h  c   
                 study 
               
               
                   
               
               
                   a  Direct thrombin inhibitors 
               
               
                   b Half-life in plasma in healthy human volunteers. 
               
               
                   c  Half-life in plasma ex vivo and in phosphate buffer 50 mM containing 1 μM de thrombin, recombinant protein 10 μM and NaCl 150 mM and 0.1% of PEG 6000 pH 7.4 for 4 h at 37° C. 
               
               
                 ND, not determined 
               
               
                   d Inhibitor of bivalent Thrombin, occupying active site and exosite 1. 
               
               
                   e The proposed one may be bivalent (single domain) or trivalent (preserved molecule) 
               
            
           
         
       
     
     Those skilled in the art will appreciate the teachings presented herein and may reproduce the invention in presented models and in other variants, embraced within the scope of attached claims.