cDNA cloning and expression of acutin

Comparative analysis of Deinagkistrodon acutus venom from Taiwan and China utilizing chromatographic, electrophoretic, and bioinformatic approaches, along with ELISA employing a monospecific antivenom

Deinagkistrodon acutus is a medically important pitviper inhabiting mainly South China and Taiwan. The hemorrhagic effects of its envenoming are compatible to its venom, which is abundant in metalloproteases (svMPs) and C-type lectin-like proteins. In this study, we investigated geographic variations in the venom of D. acutus collected from Taiwan and four Mainland Chinese provinces: Fujian, Jiangxi, Anhui, and Hunan. The variations were assessed through high-performance liquid chromatography, non-metric multidimensional scaling analysis, gel electrophoresis, and enzyme-linked immunosorbent assay (ELISA) with a monospecific antivenom (DaMAV) generated against the Taiwanese D. acutus venom, and discussed based on venom-protein sequences in databases and literature related to D. acutus venom. Additionally, the cross-reactivity of DaMAV against Crotalus horridus and Calloselasma rhodostoma venoms was investigated. We noted differential abundances of D. acutus venom metalloproteases, C-type lectin-like proteins, and phospholipase A2, along with point mutations and selective expression of serine protease isoforms. The ELISA results revealed that the venom from Taiwan was more reactive toward Taiwanese DaMAV than the four Mainland Chinese venoms, consistent with chromatographic profile differences, whereas C. horridus venom presented moderate cross-reactivity with DaMAV. The observed immunoreactivities of these venom with DaMAV can be attributed to the high prevalence of their PIII-svMPs, which are the dominant antigens, and the conservation of PIII-svMP epitopes.

Effects of hemocoagulase agkistrodon on the coagulation factors and its procoagulant activities

Objective

Hemocoagulase agkistrodon (HCA), a thrombin-like enzyme (TLE) from the venom of the Chinese moccasin snake (Deinagkistrodon acutus), has been used in clinical practice as a hemostatic compound. The aim of this study was to further investigate the pharmacological properties of HCA.

Materials and methods

Sodium dodecyl sulfate or native polyacrylamide gel electrophoresis (SDS- or N-PAGE) as well as enzyme linked immunosorbent assays (ELISAs) were conducted to study the effects of HCA on the human plasma fibrinogen and prothrombin levels, as well as its in vitro interactions with some coagulation factors. In addition, the bleeding time effects of HCA in the mouse tail-bleeding model as well as its effects on the fibrinogen levels in rabbits were determined in vivo.

Results

In vitro results revealed that HCA exerts its procoagulant activities by hydrolyzing fibrinogen into segments that are easier to be absorbed, reducing the risk of thrombus formation. Besides, HCA could significantly inhibit the activation of prothrombin at the concentration of 0.3 μM. Unexpectedly, we also found that HCA was able to strongly bind to factor X/Xa (in a ratio of 1:1) and thus inhibit the acceleration of active factor X to tissue plasminogen activator-catalyzed plasminogen activation, demonstrating that it could be less likely to lead to thrombus formation. Finally, in vivo results indicated that HCA could significantly shorten the bleeding time in the mouse tail-bleeding model and had no effect on the fibrinogen levels in rabbits.

Conclusion

In summary, HCA, a unique and new family member of TLEs, may become a new clinical drug for the prevention and treatment of hemorrhage due to its unique and complex interactions with the blood system. Clarification of these features will enable us to further understand the mechanism of action of HCA and then promote its further application in clinical practice as a therapeutic drug.

Cloning, expression, and hemostatic activities of a disintegrin, r-mojastin 1, from the mohave rattlesnake (Crotalus scutulatus scutulatus)

Interactions with exposed subendothelial extracellular proteins and cellular integrins (endothelial cells, platelets and lymphocytes) can cause alterations in the hemostatic system associated with atherothrombotic processes. Many molecules found in snake venoms induce pathophysiological changes in humans, cause edema, hemorrhage, and necrosis. Disintegrins are low molecular weight, non-enzymatic proteins found in snake venom that mediate changes by binding to integrins of platelets or other cells and prevent binding of the natural ligands such as fibrinogen, fibronectin or vitronectin. Disintegrins are of great biomedical importance due to their binding affinities resulting in the inhibition of platelet aggregation, adhesion of cancer cells, and induction of signal transduction pathways. RT-PCR was used to obtain a 216 bp disintegrin cDNA from a C. s. scutulatus snake venom gland. The cloned recombinant disintegrin called r-mojastin 1 codes for 71 amino acids, including 12 cysteines, and an RGD binding motif. r-Mojastin 1 inhibited platelet adhesion to fibronectin with an IC50 of 58.3 nM and ADP-induced platelet aggregation in whole blood with an IC50 of 46 nM. r-Mojastin 1 was also tested for its ability to inhibit platelet ATP release using PRP resulting with an IC50 of 95.6 nM. MALDI-TOF mass spectrum analysis showed that r-mojastin has a mass of 7.95676 kDa.

Purification and biochemical characterization of Eumiliin from Euphorbia milii var. hislopii latex

A protease, which we designate Eumiliin, was isolated from the latex of Euphorbia milii var. hislopii by a combination of ion-exchange chromatographic steps using DEAE-Sephacel and gel-filtration with Sephadex G-75. Eumiliin is a monomeric protein with an apparent molecular mass of 30 kDa by SDS-PAGE under reducing conditions and gave one main peak at 29,814 KDa in MALDI-TOF/TOF mass spectrometry. Eumiliin has caseinolytic and fibrinogenolytic activities, but no hemorrhagic or defibrinating activities. The enzyme readily hydrolyzes the Aalpha-chain of fibrinogen and, more slowly, the Bbeta-chain. Its fibrinogenolytic activity is inhibited by beta-mercaptoethanol and leupeptin. In contrast, EDTA and benzamidine did not affect the activity of Eumiliin. The caseinolytic activity of Eumiliin had a pH optimum of 8.0 and was stable in solution at up to 40 degrees C; activity was completely lost at >or=80 degrees C. Intraplantar injection of Eumiliin (1-25 microg/paw) caused a dose- and time-dependent hyperalgesia, which peaked 1-5h after enzyme injection. Intraplantar injection of Eumiliin (1-25 microg/paw) also caused an oedematogenic response that was maximal after 1h. Morphological analyses indicated that Eumiliin induced an intense myonecrosis, with visible leukocyte infiltrate and damaged muscle cells 24h after injection.

Isolation and characterization of the thrombin-like enzyme from Cryptelytrops purpureomaculatus venom

A thrombin-like enzyme, purpurase, was purified from the Cryptelytrops purpureomaculatus (mangrove pit viper) venom using high performance ion-exchange and gel filtration chromatography. The purified sample (termed purpurase) yielded a homogeneous band in SDS-polyacrylamide gel electrophoresis with a molecular weight of 35,000. The N-terminal sequence of purpurase was determined to be VVGGDECNINDHRSLVRIF and is homologous to many other venom thrombin-like enzymes. Purpurase exhibits both arginine ester hydrolase and amidase activities. Kinetic studies using tripeptide chromogenic anilide substrates showed that purpurase is not fastidious towards its substrate. The clotting times of fibrinogen by purpurase were concentration dependent, with optimum clotting activity at 3mg fibronogen/mL. The clotting activity by purpurase was in the following decreasing order: cat fibrinogen>human fibrinogen>dog fibrinogen>goat fibrinogen>>rabbit fibrinogen. Reversed-phase HPLC analysis of the products of action of purpurase on bovine fibrinogen showed that only fibrinopeptide A was released. Indirect ELISA studies showed that anti-purpurase cross-reacted strongly with venoms of most crotalid venoms, indicating the snake venom thrombin-like enzymes generally possess similar epitopes. In the more specific double-sandwich ELISA, however, anti-purpurase cross-reacted only with venoms of certain species of the Trimeresurus complex, and the results support the recent proposed taxonomy changes concerning the Trimeresurus complex.

Soluble expression, purification, and characterization of Gloydius shedaoensis venom gloshedobin in Escherichia coli by using fusion partners

Gloshedobin, a thrombin-like enzyme from the venom of Gloydius shedaoensis, is usually produced as inclusion bodies in Escherichia coli cell. In this work, gloshedobin was separately fused with three fusion partners NusA, GST, and TrxA at its N terminus and then was expressed as fusion proteins in E. coli. The results showed that the NusA was the most efficient fusion partner to improve the solubility of recombinant gloshedobin. The purified NusA-fused gloshedobin with an overall yield of 64.6% was resolved as one band in the SDS-PAGE gel with molecular mass of about 90 kDa. Both fibrinogen clotting and fibrinogenolytic activities were found for the recombinant product. The purified NusA-fused gloshedobin exhibited amidolytic activity of 506 U/mg under optimal conditions of pH of 8.0 and 40 degrees C. The inhibition study of NusA-fused gloshedobin by various inhibitors showed that serine protease inhibitors, phenylmethylsulphonyl fluoride, and N-tosyl-L: -phenylalanine chloromethyl ketone, strongly inhibited its admidolytic activity, whereas ethylenediaminetetraacetic acid as well as heparin and hirudin did not, suggesting that NusA-fused gloshedobin exhibited the same characteristics as the native form of gloshedobin. The strategy of this work may contribute to improve the soluble expression level of other thrombin-like enzymes from snake venom in E. coli.

Cloning of serine protease cDNAs from Crotalus durissus terrificus venom gland and expression of a functional Gyroxin homologue in COS-7 cells

Gyroxin is one of main serine proteases of Crotalus durissus terrificus venom, representing about 2% of the protein content in the crude venom. It is a 33 kDa glycoprotein with 3.8% by weight of sugar moiety. This toxin induces hemotoxicity in mice and a neurological condition called barrel rotation syndrome. In the present work, we report the molecular cloning of five new nucleotide sequences from a cDNA library of the venom glands of a single specimen of C. d. terrificus. These sequences have been analyzed in silico with respect to their cDNA organization and similarity with other snake venom serine proteases (SVSPs). We also describe a rapid and efficient method for screening vectors for mammalian cell expression, based on the fact that SVSPs are difficult-to-express toxins due to the presence of several disulfide bonds and glycosylation in their structures. Thus, one of the Gyroxin cDNAs was subcloned into pSectag2 HygroA and pED vectors and used to transfect COS-7 cells. Expression of the functional recombinant Gyroxin isoform was achieved with this cell line with esterase activity in the conditioned culture medium, as revealed by immunoblot of secreted protein and standard anti-crotalic serum from Butantan Institute.

Affinity purification of serine proteinase from Deinagkistrodon acutus venom

An affinity protocol was developed for the preparation of the main serine proteinase from Deinagkistrodon acutus venom on industrial scales. As affinity ligand, l-arginine was composed to medium and its structure was confirmed by ESI-MS analysis. The purification process consisted of one major affinity chromatography step to remove more than 95% of other proteins, and a polishing step of DEAE ion-exchange chromatography for removal of minor contaminants. The serine proteinase was 100% pure analyzed on HPLC Vydac C4 column, 99.4% on TSK G3000SW column, and 97.7% with SDS-PAGE analysis. The yield of the main serine proteinase was 3.6% of crude venom protein, the recoveries of typical fibrinogen (Fg) clotting activity and arginine esterase activity of serine proteinase were 82.2% and 84%, higher than those of other reported traditional protocols, the proteinase also showed arginine amidase activity. Reducing SDS-PAGE analysis showed that the arginine esterase was a single polypeptide with the mass of approximately 40 kDa, while MALDI-TOF-TOF-MS analysis showed that the purified proteinase should be a approximately 34 kDa glycoprotein. The desorption constant Kd and the theoretical maximum absorption Qmax on the affinity medium were 9.93 x 10(-5) and 38.1mg/g medium in absorption analysis.

Thrombin-like enzymes from venom gland of Deinagkistrodon acutus: cDNA cloning, mechanism of diversity and phylogenetic tree construction

AIM

To clone cDNAs of thrombin-like enzymes (TLEs) from venom gland of Deinagkistrodon acutus and analyze the mechanisms by which their structural diversity arose.

METHODS

Reverse transcription-polymerase chain reaction and gene cloning techniques were used, and the cloned sequences were analyzed by using bioinformatics tools.

RESULTS

Novel cDNAs of snake venom TLEs were cloned. The possibilities of post-transcriptional recombination and horizontal gene transfer are discussed. A phylogenetic tree was constructed.

CONCLUSION

The cDNAs of snake venom TLEs exhibit great diversification. There are several types of structural variations. These variations may be attributable to certain mechanisms including recombination.

Purification, primary structures and evolution of coagulant proteases from Deinagkistrodon actus venom

Deinagkistrodon (formerly Agkistrodon) actus (Taiwan) snake venom was found to contain at least seven closely related coagulant proteases. One of them, named actibin, was purified to homogeneity by means of four chromatographic steps. Actibin acted on fibrinogen to form fibrin clots with extremely high specific activity of 1,630 NIH units/mg and preferentially released fibrinopeptide A. Actibin was an acidic glycoprotein (pI 3.4) with molecular weight of 41,000, which was reduced to 28,800 after deglycosylation with N-glycanase. The k(cat)/K(m) values of actibin for hydrolysis of tosyl-l-arginine methyl ester and benzoyl-l-arginine p-nitroanilide were one-third to a half those for thrombin, reflecting a high potency of actibin in fibrinogen clotting. The amidase activities of actibin and its family proteases were inhibited by 3,4-dichloroisocoumarin, a serine protease inhibitor, indicating that actibin and its family proteases are serine proteases. Four cDNAs, named DaP1 and DaP7-DaP9, encoding D. actus coagulant proteases were cloned. All cDNAs contain an open reading frame of 780 bp coding for 260 amino acid residues, including a signal peptide of 24 amino acid residues. Their amino acid sequences predicted are highly homologous to one another with one to five amino acid substitutions. When four D. actus protease cDNAs were compared with the cDNAs coding for Trimeresurus flavoviridis and T. gramineus venom serine proteases, accelerated evolution was clearly observed. Similarity of the nucleotide sequences of four D. actus protease cDNAs with no synonymous and one to five nonsynonymous substitutions seems not to be in direct conformity with accelerated evolution. This possibly suggests that they have evolved to a similar direction to enhance their clotting activity rather than to produce other physiological activities.

The role of thioredoxin and disulfide isomerase in the expression of the snake venom thrombin-like enzyme calobin in Escherichia coli BL21 (DE3)

Thrombin-like enzymes (TLEs) are studied widely because of their therapeutic potential in myocardial infarction and thrombotic diseases. But they are always produced in Escherichia coli BL21 (DE3) as inclusion bodies because they are single chain Cys-rich proteins. In this work, coexpressing of thioredoxin (TrxA) largely increased the solubility of calobin, one of the TLEs from korea viper Agkistrodon caliginosus, but soluble calobin-T had poor enzyme activity. Disulfide isomerase (DsbC) was introduced into the host cell and coexpressed with calobin in the presence of TrxA, the result was that both the solubility and enzyme activity of calobin-TD were higher than those of calobin-T. Although recombinant calobins exhibited the enzyme of hydrolyzing the fibrinogen, they lost clotting activity to the substrate. Recombinant calobin-TD remained poor amidolytic activity, the effects of divalent metal cations and various inhibitors on this activity were similar to those of native calobin nevertheless, suggesting that calobin-TD exhibited the characteristics of serine protease especially of trypsin-like serine protease.

Snake venom serine proteinases: sequence homology vs. substrate specificity, a paradox to be solved

Snake venom glands synthesize a variety of serine proteinases capable of affecting the haemostatic system. They act on macromolecular substrates of the coagulation, fibrinolytic, and kallikrein-kinin systems, and on platelets to cause an imbalance of the haemostatic system of the prey. In this review we describe their biochemical/biophysical characteristics, biological activities as well as aspects of their evolution and structure-activity relationship.

Functional characterization of recombinant batroxobin, a snake venom thrombin-like enzyme, expressed fromPichia pastoris

A thrombin-like enzyme of Bothrops atrox moojeni venom, batroxobin, specifically cleaves fibrinogen alpha chain, resulting in the formation of non-crosslinked fibrin clots. The cDNA encoding batroxobin was cloned, expressed in Pichia pastoris and the molecular function of purified recombinant protein was also characterized. The recombinant batroxobin had an apparent molecular weight of 33 kDa by SDS-PAGE analysis and biochemical activities similar to those of native batroxobin. The purified recombinant protein strongly converted fibrinogen into fibrin clot in vitro, and shortened bleeding time and whole blood coagulation time in vivo. However, it did not make any considerable alterations on other blood coagulation factors. Several lines of experimental evidence in this study suggest that the recombinant batroxobin is a potent pro-coagulant agent.

cDNA cloning and characterization of Agkistin, a new metalloproteinase from Agkistrodon halys

Agkistin was a new snake venom metalloproteinase (SVMP) gene which was cloned from Agkistrodon halys. Its deduced amino acid sequence has two additional cysteines (Cys407 and Cys426) in the disintegrin domain compared to other RGD containing SVMPs. The full-length gene (Agkistin) and its disintegrin region (named Agkistin-s) were expressed by baculovirus expression system (pFastBac-Htb vector) with His-tag, and their platelet aggregation-inhibition activity was evaluated. The expressed protein Agkistin can also induce apoptosis of HMEC cells in the basal medium after incubated at 37 degrees C for 20 h.

Biochemical characterization of a thrombin-like enzyme and a fibrinolytic serine protease from snake (Agkistrodon saxatilis) venom

A thrombin-like enzyme and a fibrinolytic serine protease were purified to homogeneity from the venom of a Korean snake Agkistrodon saxatilis emelianov. Both the purified enzymes migrated as a single protein band corresponding to 39 kDa in SDS-PAGE. However, the molecular mass was reduced to 28 kDa by enzymatic removal of the N-linked carbohydrates in those two different enzyme species. Although the thrombin-like enzyme and the fibrinolytic protease show homologous features in their molecular sizes and N-terminal amino acid sequences, yet they can be clearly distinguished from each other in terms of substrate specificity, susceptibility to inhibitors and fibrinogen degradation. It is postulated that these two enzymes are capable of functioning in a cooperative manner to effectively remove fibrinogen and consequently to reduce the blood viscosity.

Serine protease isoforms of Deinagkistrodon acutus venom: cloning, sequencing and phylogenetic analysis

The major coagulating fibrinogenase of Deinagkistrdon acutus venom, designated acutobin, was purified by anion-exchange chromatography, gel filtration and reverse-phase HPLC. Approximately 80% of its protein sequence was determined by sequencing the various fragments derived from CNBr cleavage and digestion with endoprotease. Extensive screening of the venom gland cDNA species after amplification by PCR resulted in the isolation of four distinct cDNA clones encoding acutobin and three other serine proteases, designated Dav-PA, Dav-KN and Dav-X. The complete amino acid sequences of these enzymes were deduced from the cDNA sequences. The amino-acid sequence of acutobin contains a single chain of 236 residues including four potential N-glycosylation sites. The purified acutobin (40 kDa) contains approx. 30% carbohydrate by weight, which could be partly removed by N-glycanase. The phylogenetic tree of the complete amino acid sequences of 40 serine proteases from 18 species of Crotalinae shows functional clusters reflecting parallel evolution of the three major venom enzyme subtypes: coagulating enzymes, kininogenases and plasminogen activators. The possible structural elements responsible for the functional specificity of each subtype are discussed.

Purification, characterization, and cDNA sequence of halysetin, a disintegrin-like/cysteine-rich protein from the venom of Agkistrodon halys Pallas

By means of DEAE-Sepharose CL-6B column chromatography, gel filtration on Sephadex G-75 and Superose 12 FPLC, halysetin, an antiplatelet protein, was purified from the venom of Agkistrodon halys Pallas with molecular mass of 29 kDa on SDS-PAGE and 23,168 Da by mass spectrometry. The p1 was about 5.0. Halysetin was devoid of phospholipase A2, fibrino-(geno)lytic, esterase, hemorrhagenic activities. Halysetin dose-dependently inhibited the aggregation of human platelet, which was stimulated by collagen with IC50 of 420 nM, but not that stimulated by ADP. The N-and C-terminal sequences of halysetin were characterized. Its full-length cDNA was cloned by RT-PCR from the total RNA extracted from the snake venom gland. It encoded a protein of 212-amino-acid residues with disintegrin-like/cysteine-rich domains and was highly homologous with SYMPs (snake venom metalloprotease).

Expression of a kallikrein-like protease from the snake venom: engineering of autocatalytic site in the fusion protein to facilitate protein refolding

In order to circumvent the difficulty encountered in the expression and purification of the recombinant products in E. coli system, we have developed a novel and facile method of removing the polyhistidine tag from target proteins after heterologous gene expression. The expression of a serine protease (Tm-5) from Taiwan habu (Trimeresurus mucrosquamatus) is taken as an exemplar to illustrate the basic rationales and protocols involved. In place of an enterokinase recognition site, a polyhistidine tag linked to an autocatalyzed site based on cleavage specificity of the serine protease flanking on the 5'-end of Tm-5 clone sequence was engineered before protein expression in E. coli system. Renaturation of the fusion protein after expression revealed that the recombinant protease had refolded successfully from the inclusion bodies. Upon autocleavage of the expressed protease, the polyhistidine tag with additional amino acid residues appended to the N-terminus of the coding sequence is found to be removed accordingly. The protein expressed and purified by this new strategy possesses a molecular weight of approximately 28,000 in accord with the expected value for this venom protease. Further characterization of the recombinant protein employing a variety of techniques which include immunoblot analysis, RP-HPLC, ESI-MS, and N-terminal amino acid sequencing all shows indistinguishable properties to those of the isolated native protease. Most noteworthy is that the recombinant Tm-5 protease also exhibits amidase activity against N-benzoyl-Pro-Phe-Arg-p-nitroanilide, a unique and strict substrate for native Tm proteases reported previously.

Molecular cloning and sequence analysis of a cDNA for factor V activating enzyme

The complete amino acid sequence of a factor V activator (VLFVA) is deduced from the nucleotide sequence of a cDNA encoding the enzyme. The cDNA was isolated by PCR screening a venomous gland cDNA library of Central Asian Vipera lebetina snake. The full-length cDNA clone, derived from two overlapping fragments, comprises 1563 basepairs which encode an open reading frame of 259 amino acids. The amino acid sequence of VLFVA (235 amino acids) shows significant homology with snake venom and mammalian serine proteinases. It contains 12 half-cysteines which form, by analogy with other serine proteinases, 6 disulfide bridges. VLFVA has the catalytic triad His43-Asp88-Ser182. The amino terminal amino acid valine is preceded by 24 amino acids: a putative signal peptide of 18, mainly hydrophobic, amino acids and an activating peptide of 6, mainly hydrophilic amino acid residues. This is the first cloned factor V activating enzyme from snake venom.