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

Abstract

A class of proteins that inhibit thrombin, particularly direct inhibitor of thrombin modified from sculptin, identified in the transcriptomics analysis of the salivary glands of ticks, as well as fragments and recombinant protein thereof, which can be used as anticoagulant agents and for the prophylaxis and/or treatment of thromboembolic diseases. These proteins fall within the fields of biochemistry, molecular biology, genetics, pharmacy and medicinal chemistry, being related to biochemical and metabolic processes.

Claims

1. A recombinant protein, comprising one sequence selected from the group consisting of 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, and SEQ ID NO: 16.

2. The recombinant protein according to claim 1, consisting of one sequence selected from the group consisting of 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, and SEQ ID NO: 16.

3. (canceled)

4. (canceled)

5. A process for obtaining recombinant protein comprising one sequence selected from the group consisting of 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, and SEQ ID NO: 16, comprising obtaining the recombinant protein from the salivary gland cDNA from the tick Amblyomma cajennense.

6. (canceled)

7. (canceled)

8. A synthetic gene comprising one sequence represented by SEQ ID NO: 17.

9. The synthetic gene according to claim 8, consisting of one sequence represented by SEQ ID NO: 17.

10. A method for prophylaxis and/or treatment of thromboembolic diseases, comprising preparing a medication or pharmaceutical composition of sculpin or a recombinant protein comprising one sequence selected from the group consisting of 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, and SEQ ID NO: 16, wherein the medication or pharmaceutical composition is used for prophylaxis and/or treatment of thromboembolic diseases.

11. A method for prophylaxis and/or treatment of thromboembolic diseases and/or as a direct and specific thrombin inhibitor, comprising using sculpin or a recombinant protein comprising one sequence selected from the group consisting of 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, and SEQ ID NO: 16 for prophylaxis and/or treatment of thromboembolic diseases and/or as a direct and specific thrombin inhibitor.

Description

BRIEF DESCRIPTION OF FIGURES

[0062] 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.

[0063] FIG. 2 shows the specificity of recombinant protein for thrombin and its dose dependency, and IC.sub.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).

[0064] 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).

[0065] 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).

[0066] 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.

[0067] 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).

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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

[0073] 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.

[0074] The present invention has the inventive concept common to several objects thereof the inhibitors of thrombin, particularly direct thrombin inhibitors and fragments thereof.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] In one embodiment, synthetic gene comprises one sequence with SEQ ID NO: 17.

[0083] In one embodiment, synthetic gene consists of one sequence with SEQ ID NO: 17.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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).

[0089] 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

[0090] Examples shown herein aim solely exemplify one from several ways to implement the invention, however without limitation of the scope thereof by no means.

[0091] Amino acid sequence of sculptin was identified from analysis of cDNA library of salivary gland from tick Amblyomma cajennense (currently Amblyomma sculptum).

[0092] 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).

[0093] 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).

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] Suspension was centrifuged at 16000 rpm (4° C.) for one hour in order to split insoluble material from soluble material.

[0101] 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).

[0102] 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

[0103] 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. 8A). 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

[0104] 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. 10A and 10B). Purified recombinant protein was used for additional experiments (image inserted in FIG. 2A).

Recombinant Protein is a Thrombin-Specific Inhibitor

[0105] 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. 2A). For the other hand, recombinant protein (1, 100, 200 nM) did not inhibit factor Xa, trypsin and plasmin (FIG. 2A).

Inhibition of Thrombin Residual Activity by Recombinant Protein and Calculation of IC.SUB.50 .Value

[0106] 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. 2B-D). Percentage plot of inhibition versus concentration log was adjusted in dose-response function of equation 1 and IC.sub.50 value of 86.6±1.9 pM was calculated (FIG. 3D).

Kinetics Thrombin Inhibition by Recombinant Protein

[0107] 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. 3A. 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. 3B). 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. 3C) and it was even confirmed by data adjustment to nonlinear regression for competing enzyme inhibition using equations 3 and 4 (FIG. 3D). Ki value of 18.1±1.7 pM obtained through this method was similar to that calculated previously (FIG. 4D).

Binding Kinetics of Recombinant Protein to Thrombin

[0108] 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. 4A). In addition, fractional speeds were plotted versus inhibitor concentrations using equation 5 of Morrison tight binding and data is best suited in equation (FIG. 4B). 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.sub.obs calculated using equation 6 was plotted versus recombinant protein concentration. From the plot, k.sub.on and k.sub.off were calculated which resulted in 4.04±0.03×10.sup.7 M.sup.−1 s.sup.−1 and 0.65±0.04×10.sup.−3 s.sup.−1 respectively (FIG. 4C). Inhibition constant (Ki) of 16.1±1.4 pM was calculated using equation 7.

Degradation of Recombinant Protein by Serine Proteases

[0109] 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. 5A). 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. 5A). Accordingly, following the same incubation time, factor Xa also converted the recombinant protein in fragments (FIG. 5A). 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. 5B). 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. 5B). Interestingly, recombinant protein digested with factor Xa retained its thrombin inhibition activity (FIG. 5B). 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. 5C). 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. 5D). However, recombinant protein incubated with thrombin, plasmin and trypsin did not inhibit thrombin (FIG. 5D). Interestingly, recombinant protein incubated by factor Xa even inhibited the thrombin activity (FIG. 5D).

Sequencing N-Terminal of Recombinant Protein Hydrolyzed by Thrombin

[0110] 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. 5E). Sequenced residues for the following three peaks (2.sup.nd 3.sup.rd and 4.sup.th) were MPKGG, being basically N-terminal residues of recombinant protein peptides generated by thrombin (FIG. 5E). 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. 5E). 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-US-00001 TABLE 1 Recombinant protein fragments generated by thrombin. Theoretical Calculated Peak Mass Mass.sup.c number.sup.a Recombinant protein fragment .sup.b [MH]+ [MH]+ H1 GKPQGHPHDALEARSDAVHTAVPK (SEQ 2518.77 2521.74 ID NO: 2) GKPQGHPHDALEARSDAVHTAVPKMPK 6162.85 6169.56 GGHGGFEPIPIDYDERALEARSDAVHTAV PK (SEQ ID NO: 3) H2 MPKGGHGGFEPIPIDYDERALEARSDAVH 3663.09 3663.90 TAVPK (SEQ ID NO: 4) H3 MPKGGHGGFEPIPIDYDERALHALEHHHH 3572.92 3572.70 HH (SEQ ID NO: 5) H5 MPKGGHGGFEPIPIDYDERALEARSDAVH 7217.00 7202.66 TAVPKMPKGGHGGFEPIPIDYDERALHAL EHHHHHH (SEQ ID NO: 6) H6 MPKGGHGGFEPIPIDYDERALEARSDAVH 7282.19 7261.19 TAVPKMPKGGLGGFEPIPIDYDERALEAR SDAVHTAVPK (SEQ ID NO: 7) MPKGGLGGFEPIPIDYDERALEARSDAVH 10837.10 10807.97 TAVPKMPKGGHGGFEPIPIDYDERALEAR SDAVHTAVPKMPKGGHGGFEPIPIDYDER ALHALEHHHHHH (SEQ ID NO: 8) MPKGGHGGFEPIPIDYDERALEARSDAVH 14481.18 14431.37 TAVPKMPKGGLGGFEPIPIDYDERALEAR SDAVHTAVPKMPKGGHGGFEPIPIDYDER ALEARSDAVHTAVPKMPKGGHGGFEPIPI DYDERALHALEHHHHHH (SEQ ID NO: 9) GKPQGHPHDALEARSDAVHTAVPKMPK 16981.94 16990.90 GGHGGFEPIPIDYDERALEARSDAVHTAV PKMPKGGLGGFEPIPIDYDERALEARSDA VHTAVPKMPKGGHGGFEPIPIDYDERALE ARSDAVHTAVPKMPKGGHGGFEPIPIDYD ERALHALEHHHHHH (SEQ ID NO: 1)

[0111] 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

[0112] 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. 5F). Sequenced residues for the next two peaks (2.sup.nd and 3.sup.rd) were SDAVH, which are in fact N-terminal residues of recombinant protein peptides generated by factor Xa (FIG. 5F). The last peak (4.sup.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. 5F). 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-US-00002 TABLE 2 Recombinant protein fragments generated by factor Xa. Peak Recombinant protein Theo- reti- Calcu- cal lated number fragmentation Mass Mass H1 GKPQGHPHDALEARSDAVHTAVPKM 5156.74 5153.57 PKGGHGGFEPIPIDYDERALEAR (SEQ ID NO: 10) H2 SDAVHTAVPKMPKGGHGGFEPIPIDY 3663.10 3667.50 DERALEAR (SEQ ID NO: 11) SDAVHTAVPKMPKGGHGGFEPIPIDY 4579.05 4582.40 DERALHALEHHHHHH (SEQ ID NO: 12) H3 SDAVHTAVPKMPKGGHGGFEPIPIDY 8223.13 8220.55 DERALEARSDAVHTAVPKMPKGGHG GFEPIPIDYDERALHALEHHHHHH (SEQ ID NO: 13) SDAVHTAVPKMPKGGHGGFEPIPIDY 6765.55 6770.60 DERALEARSDAVHTAVPKMPKGGHG GFEPIPIDYDER (SEQ ID NO: 14) H4 SDAVHTAVPKMPKGGHGGFEPIPIDY 7306.17 7299.61 DERALEARSDAVHTAVPKMPKGGHG GFEPIPIDYDERALEAR (SEQ ID NO: 15) GKPQGHPHDALEARSDAVHTAVPKM 12420.90 12427.54 PKGGHGGFEPIPIDYDERALEARSD AVHTAVPKMPKGGLGGFEPIPIDYD ERALEARSDAVHTAVPKMPKGGHGG FEPIPIDYDERALEAR (SEQ ID NO: 16) GKPQGHPHDALEARSDAVHTAVPKM 16981.94 16990.90 PKGGHGGFEPIPIDYDERALEARSD AVHTAVPKMPKGGLGGFEPIPIDYD ERALEARSDAVHTAVPKMPKGGHGG FEPIPIDYDERALEARSDAVHTAVP KMPKGGHGGFEPIPIDYDERALHAL EHHHHHH (SEQ ID NO: 1)

[0113] 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

[0114] In addition, recombinant protein was incubated with factor Xa for 18 h and resulting peptides were split by reverse phase chromatography (FIG. 6A). Peaks (named as H1, H2, H3 H4 and H5) were gathered and undergone to mass spectrometry MALDI-TOF (FIG. 6B). 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. 6B, Table 1). Further, fractions (H1, H2, H3 and H4) were undergone to test of thrombin inhibition (FIG. 6C). 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. 6D). 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

[0115] 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. 11A and 11B). Maximum test reading for aPTT was achieved following 12 nM, while for PT that was achieved following 6 nM of recombinant protein (FIGS. 11A and 11B). For the other hand, TT was prolonged by recombinant protein in peak-molar range (FIG. 11C).

TABLE-US-00003 TABLE 3 Comparison of biochemical proprieties of thrombin inhibitors. Inhibitor.sup.a Inhibition Type K.sub.i Value Administration Half-life.sup.b Ref. Recombinant Competing 19 ± 2 pM Intravenously 1.3 h [.sup.11,12] Hirudin.sup.d Sulfo-hirudin.sup.d Competing 1.2 ± 0.2 pM ND ND [.sup.26,43] Hirugen.sup.d No competing 1.3 ± 0.2 μM ND ND [.sup.24] Bivalirudin.sup.d No competing 1.9 ± 2.6 nM Intravenously 25 min [.sup.13,25,26] Argatroban No competing 39 ± 2 nM Intravenously 50 min [.sup.23] Recombinant Competing 18.5 ± 2.2 pM ND ND This protein 8 h .sup.c study .sup.a Direct thrombin inhibitors .sup.bHalf-life in plasma in healthy human volunteers. .sup.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 .sup.dInhibitor of bivalent Thrombin, occupying active site and exosite 1. .sup.eThe proposed one may be bivalent (single domain) or trivalent (preserved molecule)

[0116] 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.