BJ-PI2, A non-hemorrhagic metalloproteinase from Bothrops jararaca snake venom

Background

Envenoming by Bothrops jararaca can result in local pain, edema, hemorrhage and necrosis, partially mediated by snake venom metalloproteinases (SVMPs). Here, we describe the characterization of BJ-PI2, a P-I class SVMP from B. jararaca venom, and its local tissue actions.

Methods

BJ-PI2 was purified by a combination of gel filtration, anion-exchange chromatography and reverse phase HPLC, and identified by mass spectrometry. Clotting and fibrin(ogen)olytic activities were assayed using conventional methods. Hemorrhagic activity and changes in vascular permeability were examined in rat dorsal skin. Myonecrosis and inflammatory activity were examined in mouse gastrocnemius muscle.

Results

BJ-PI2 was a 23.08 kDa single-chain polypeptide. Tryptic fragments showed highest homology with SVMP insularinase A from Bothrops insularis, but also with B. jararaca SVMP bothrojaractivase; less similarity was observed with B. jararaca SVMPs BJ-PI and jararafibrases II and IV. BJ-PI2 did not clot fibrinogen or rat citrated plasma but had α- and β-fibrinogenolytic activity (inhibited by EDTA and 1,10-phenanthroline but not by PMSF) and attenuated coagulation after plasma recalcification. BJ-PI2 had fibrinolytic activity. BJ-PI2 increased the vascular permeability of rat dorsal skin (inhibited by 1,10-phenanthroline). BJ-PI2 was not hemorrhagic or myonecrotic but caused migration of inflammatory cells. In contrast, venom was strongly hemorrhagic and myonecrotic but caused less infiltration of inflammatory cells.

Conclusions

BJ-PI2 is a non-hemorrhagic, non-myonecrotic, non-coagulant P-I class SVMP that may enhance vascular permeability and inflammatory cell migration in vivo.

General significance

BJ-PI2 contributes to enhanced vascular permeability and inflammatory cell migration after envenoming, but not to venom-induced hemorrhage and necrosis.     

Isolation and Properties of a New Kallikrein Inhibitor from Tityus serrulatus Venom

The kallikrein inhibitor-peptide content of Tityus serrulatus scorpion crude venom was purified by Sephadex G-50 and Sephadex G-25 fine gel filtration chromatographies, followed by two steps of reverse-phase column on HPLC. The isolated inhibitor peptide was homogeneous in its N-terminal and partial amino acid sequence, showing a molecular weight of 4.489 Da by mass spectrometry and amino acid analysis. The peptide was tested with rat plasma and urine kallikrein, which resulting in an inhibition with similar afinity to both enzymes, showing an IC₅₀ of 14.3 M after 13 and 8 min, respectively, using kininogen as substrate on the isolated guinea-pig ileum bioassay. The porcine pancreatic kallikrein showed after 10 min an IC₅₀ value of 12.6 M with H-D-Val-Leu-Arg-pNA HCl as substrate. In addition, the isolated peptide significantly inhibited porcine pancreatic kallikrein with values in the range of apparent or absolute calculated peptide K _i = 2.5 M. The inhibitor was heat resistant and stable at pH values less than 5.     

Evaluation of the effect of aqueous extract of Croton urucurana Baillon (Euphorbiaceae) on the hemorrhagic activity induced by the venom of Bothrops jararaca, using new techniques to quantify hemorrhagic activity in rat skin

Aqueous extracts of Croton urucurana (Sangra D'agua), a plant popularly considered a cicatrizant, were analyzed for anti-Bothrops jararaca venom activity. The plant extracts antagonized the hemorrhagic activity of the venom and proanthocyanidins were involved in this activity. Two new methods for the quantification of hemorrhagic activity evoked by bothropic venoms were employed. The first consists of graphic computer analysis of the hemorrhagic halo evoked in rats by dorsal intradermic administration of venom. The second method involves quantification of the hemoglobin present in the hemorrhagic halo. Based on the results, we suggest that these methods, easily implemented in the laboratory routine, allow for quantification of venom-induced hemorrhagic activity. In addition, this study demonstrates that the rich extracts of proanthocyanidins are powerful inhibitors of bothropic venom metalloproteinases.     

Inhibition of the myotoxic activity of Bothrops jararacussu venom and its two major myotoxins, BthTX-I and BthTX-II, by the aqueous extract of Tabernaemontana catharinensis A. DC. (Apocynaceae)

Partial neutralization of the myotoxic effect of Bothrops jararacussu venom (BV) and two of its myotoxins [bothropstoxin-I (BthTX-I), catalytically inactive, and II (BthTX-II), showing low PLA2 activity], by the lyophilized aqueous extract of Tabernaemontana catharinensis (AE), was studied in rat isolated soleus muscle preparations (in vitro) and through i.m. injection in the gastrocnemius muscle (in vivo) by determination of creatine kinase (CK) activity and histopathological analysis. Incubation of soleus muscle for 1 h with BV or toxins (20 microg/ml) plus AE (400 microg/ml) added immediately after BV, BthTX-I or BthTX-II reduced CK levels by 53%, 37% and 56%, respectively. The myonecrotic effects of BV (20 microg/ml) upon soleus muscle was reduced 24%, 35% and 36% when AE (400 microg/ml) was added 1 h after BV and CK was evaluated 30 min, 1 and 2 h later, respectively. For BthTX-I these values were 46%, 48% and 47%, while for BthTX-II no inhibitory effect was detected. Histological analysis of soleus muscle after incubation with AE (400 microg/ml, 1 h) did not reveal any change in muscle fibers, but severe necrosis induced by BV or toxins (20 microg/ml) was clearly in evidence, and decreased significantly when soleus muscle was protected by AE. This protection was also observed when AE was administered 1 h after BV or BthTX-I, but not after BthTX-II. AE did not inhibit the catalytic PLA2 activity of BthTX-II or BV and did not change the PAGE pattern of BV, BthTX-I or BthTX-II. In vivo assays were performed in 100-g rats and maximal CK release was attained at a dose of 100 microg of BV, 3 h after injection. AE was not effective when injected 20 s after BV or toxins. However, injecting BV or toxins (100 microg), which were pre-incubated with AE (2 mg) caused an inhibition of 57%, 59% and 51%, respectively, with zero time pre-incubation, but was less effective with 1 h pre-incubation. This plant represents a potential source of promising myotoxin inhibitors.     

Expression pattern of three-finger toxin and phospholipase A2 genes in the venom glands of two sea snakes, Lapemis curtus and Acalyptophis peronii : comparison of evolution of these toxins in land snakes, sea kraits and sea snakes

Background  

Snake venom composition varies widely both among closely related species and within the same species, based on ecological variables. In terrestrial snakes, such variation has been proposed to be due to snakes' diet. Land snakes target various prey species including insects (arthropods), lizards (reptiles), frogs and toads (amphibians), birds (aves), and rodents (mammals), whereas sea snakes target a single vertebrate class (fishes) and often specialize on specific types of fish. It is therefore interesting to examine the evolution of toxins in sea snake venoms compared to that of land snakes.     

Novel svVEGF isoforms from Macrovipera lebetina venom interact with neuropilins

Increased vascular permeability and vasodilation are responses usually elicited by snake envenomation. In this report, we isolated from Macroviperalebetina venom two protein groups designated IC1 (Increasing Capillary1) and IC2 based on their activities on capillary permeability. Mass spectrometry analysis showed that IC1 contained four major proteins of 23,650, 24,306, 24,589 and 24,718 Da, whereas IC2 contained three major proteins of 25,101, 25,194 and 25,298 Da. N-terminal amino-acid sequencing revealed that IC1 and IC2 belong to the snake venom VEGF (svVEGF) family. IC1 and IC2 had a marked specificity for VEGFR-2, with affinities in the nanomolar range. Interestingly, they also bind to NRP1 and NRP2, with affinities in the micromolar range. This is the first report demonstrating that M. lebetina encodes several distinct svVEGFs, endowed with a capacity to interact with neuropilins. IC1 and IC2 could be valuable tools to understand the molecular properties of angiogenic factors and their receptors.     

Purification and properties of a coagulant thrombin-like enzyme from the venom of Bothrops leucurus

A thrombin-like enzyme from Bothrops leucurus venom, named leucurobin (leuc), was purified by gel filtration, affinity and ion exchange chromatographies. Physicochemical studies indicated that the purified enzyme is a 35 kDa monomeric glycoprotein on SDS-PAGE under reducing conditions, which decreased to 29 kDa after deglycosylation with N-glycosidase F (PNGase F). The amino acid sequence of leuc was determined by automated sequencing of the intact native protein and peptides produced by digestion of the S-pyridyl-ethylated protein with trypsin. The protein sequence exhibits significant similarities with other serine proteases reported from snake venoms, and contains two potential sites of N-linked glycosylation. The proteinase split off fibrinopeptide A (FPA) rapidly from human fibrinogen; however, only negligible traces of fibrinopeptide B (FPB) were observed. In addition, the enzyme released the N-terminal peptide (Mr = 4572) containing the first 42 residues from the Bβ-chain. Leuc could neither activate factor XIII nor release kinins from heat-treated bovine plasma. Its specific clotting activity was equivalent to 198 NIH thrombin U/mg on human fibrinogen. Kinetic properties of leuc were determined using representative chromogenic substrates. The enzyme evoked the gyroxin syndrome when injected into the tail veins of mice at levels of 0.143 μg/g mouse. The inhibitory effects of PMSF and benzamidine on the amidolytic activity suggest that leuc is a serine proteinase, and inhibition by β-mercaptoethanol revealed the important role of the disulfide bonds in the stabilization of the native structure. Antibothropic serum, SBTI and EDTA had little or no effect on its amidolytic activity. However, the clotting effect of the enzyme was strongly inhibited by antibothropic serum. A Dixon plot showed that the hydrolysis of Bz-l-Arg-pNA by leuc was competitively inhibited by benzamidine (K_i = 1.61 ± 0.25 mM).     

The complete amino acid sequence of a hirudin variant from the leechHirudinaria manillensis

Unlike the European leechHirudo medicinalis, the Asian jawed leechHirudinaria manillensis is specialized for feeding on mammalian blood. In the salivary glands of both these leeches, there is a potent inhibitor of thrombin, called hirudin, which acts as an anticoagulant. We have reported previously the isolation and purification of a variant of hirudin, called bufrudin, from the head portions ofHirudinaria. In the present study, the complete amino acid sequence of bufrudin was determined by automated Edman degradation of peptide fragments generated after cleavage of protein with trypsin or thermolysin. Comparison of the primary structure of bufrudin, with hirudin HV1, show about 70% sequence identity with deletion of two amino acids, but the key amino acids at the C-terminus, involved in the inhibition of thrombin, are conserved. However, similar sequence comparison of bufrudin with hirullin P18, a hirudin variant isolated from the same leech species but from whole leech, instead of heads, reveals even less sequence identity of about 60%. From the amino acid sequence, it is suggested that the conformation of the C-terminal portion of bufrudin may be significantly different from hirullin P18, but similar to hirudin HV1, upon its interaction with thrombin. These results indicate that, as withHirudo leech, various isoforms of hirudin also exist inHirudinaria leech, with a significant change occurring in the structure of the molecule during the evolution of leeches.     

Variation of individual electromorphs in Microtus pennsylvanicus and Peromyscus leucopus

Blood samples were taken from individual meadow voles (Microtus pennsylvanicus) and white-footed mice (Peromyscus leucopus) every three weeks. Two serum proteins, albumin and transferrin, were examined using acrylamide electrophoresis and densitometry. In individuals of both species, electrophoretic mobility and banding pattern changed. Such changes have been documented in other proteins, and may reflect changes in the internal or external environment of the individuals. Individual changes in serum proteins may seriously affect their interpretation, when used as genetic markers in population studies.     

Protein analysis of an individual Caenorhabditis elegans single-cell embryo by capillary electrophoresis

We present a simple one-dimensional electrophoretic map of the expressed proteins in a Caenorhabditis elegans embryo. The embryo was taken from an adult nematode, injected into a 50-μm I.D. capillary, and lysed. The proteins were fluorescently labeled and then separated by capillary electrophoresis and detected by laser-induced fluorescence. Over 20 components were resolved in the 22-min separation. The dynamic range was outstanding for this separation, noise in the baseline was less than 0.01% the amplitude of the largest component.     

The Amino Acid Sequence of Bothropstoxin-II, an Asp-49 Myotoxin from Bothrops jararacussu (Jararacucu) Venom with Low Phospholipase A2 Activity

The complete amino acid sequence of bothropstoxin-II (BthTX-II), a myotoxin isolated from Bothrops jararacussu snake venom, is reported. The results show that BthTX-II is an Asp-49 phospholipase A₂ (PLA₂)-like protein composed of a single polypeptide chain of 120 amino acid residues (M _r = 13,976), containing one methionine and 14 half-cystines. Despite a high degree of homology with other PLA₂'s and the presence of the strategic residues known to compose the Ca²⁺-binding loop, namely Tyr-28, Gly-30, Gly-32, and especially Asp-49, besides His-48, Tyr-52, and Asp-99, all of them directly or indirectly involved in catalysis, BthTX-II revealed a very low PLA₂ activity when assayed on egg yolk phosphatidylcholine. We attribute this low catalytic activity to the existence of extra mutations, e.g., Trp-5 for Phe-5, which points to the need of considering other strategic positions, since only Lys-49 PLA₂'s have been considered to be devoid of this enzymatic activity.     

Sequence of a new Bowman-Birk inhibitor fromTorresea acreana seeds and comparison withTorresea cearensis trypsin inhibitor (TcTI2)

TaTI (Torresea acreana trypsin inhibitor), a new member of the Bowman-Birk trypsin inhibitor family, was purified from seeds ofTorresea acreana, one of the two known species ofTorresea, a Brazilian native Leguminosae of the Papilionoideae subfamily. Purification was performed by acetone fractionation, anion-exchange chromatography, and gel filtration. The TaTI appears asM_r 7000 in SDS-PAGE under reducing conditions. There are 63 amino acid residues present in the TaTI sequence, which was confirmed by mass spectrometry (8388 daltons). The putative reactive sites residues were Lys-15 and Arg-42 at the first and second site, respectively. The antibodies raised against TcTI2,Torresea cearensis trypsin inhibitor 2, showed a cross-reaction with TaTI, but not with other Bowman-Birk inhibitors purified from Leguminosae. The inhibition constants of TaTI and TcTI2 were comparable when measured against trypsin, chymotrypsin, and factor XIIa, but not on plasmin. The latter was tenfold more effectively inhibited by TcTI2 then by TaTI. Neither TaTI nor TcTI2 affects thrombin, plasma kallikrein, or factor Xa.     

Three angiotensin-converting enzyme inhibitors from Rabdosia coetsa

The EtOAc extract of Rabdosia coetsa showed angiotensin-converting enzyme (ACE) inhibitory activity. Bioassay-guided isolation of this extract yielded ethyl caffeate (1), rosmarinic acid (2) and methyl rosmarinate (3), which inhibited ACE activity by 32.42%, 55.19% and 39.50% respectively, at the concentration of 10 μg/ml.     

Snake venomics and antivenomics of Bothrops atrox venoms from Colombia and the Amazon regions of Brazil, Perú and Ecuador suggest the occurrence of geographic variation of venom phenotype by a trend towards paedomorphism

The venom proteomes of Bothrops atrox from Colombia, Brazil, Ecuador, and Perú were characterized using venomic and antivenomic strategies. Our results evidence the existence of two geographically differentiated venom phenotypes. The venom from Colombia comprises at least 26 different proteins belonging to 9 different groups of toxins. PI-metalloproteinases and K49-PLA₂ molecules represent the most abundant toxins. On the other hand, the venoms from Brazilian, Ecuadorian, and Peruvian B. atrox contain predominantly PIII-metalloproteinases. These toxin profiles correlate with the venom phenotypes of adult and juvenile B. asper from Costa Rica, respectively, suggesting that paedomorphism represented a selective trend during the trans-Amazonian southward expansion of B. atrox through the Andean Corridor. The high degree of crossreactivity of a Costa Rican polyvalent (Bothrops asper, Lachesis stenophrys, Crotalus simus) antivenom against B. atrox venoms further evidenced the close evolutionary kinship between B. asper and B. atrox. This antivenom was more efficient immunodepleting proteins from the venoms of B. atrox from Brazil, Ecuador, and Perú than from Colombia. Such behaviour may be rationalized taking into account the lower content of poorly immunogenic toxins, such as PLA₂ molecules and PI-SVMPs in the paedomorphic venoms. The immunological profile of the Costa Rican antivenom strongly suggests the possibility of using this antivenom for the management of snakebites by B. atrox in Colombia and the Amazon regions of Ecuador, Perú and Brazil.     

Molecular analysis of theArabidopsis pattern formation geneGNOM: gene structure and intragenic complementation

TheGNOM gene is required for pattern formation along the main body axis of the embryo in the flowering plantArabidopsis thaliana. Mutations in theGNOM gene alter the asymmetric division of the zygote and interfere with the formation of distinct apical-basal regions in the developing embryo. We have isolated theGNOM gene by positional cloning, characterised its structure and determined the molecular lesions in mutant alleles. Although the predicted 163 kDa GNOM protein has a conserved domain in common with the yeast secretory protein Sec7p, it is most closely related in size and overall similarity to the product of the yeastYEC2 gene, which is not essential for cell viability. Four fully complementinggnom alleles carry missense mutations in conserved regions, seven partially complementing alleles have premature stop codon mutations and two non-complementing alleles have splice-site lesions. Our results suggest that the GNOM protein acts as a complex of identical subunits and that partial complementation may involve low levels of full-length protein generated by inefficient translational read-through.Communicated by H. Saedler     

Purification and characterization of insecticidal toxins from venom glands of the parasitic wasp, Bracon hebetor

The potency of venom from Bracon hebetor against lepidopterous larvae has been known for over 40 years, but previous attempts to purify and characterize individual protein toxins have been largely unsuccessful. Three protein toxins were purified from venom of this small parasitic wasp and the amino acid sequences of 22–31 consecutive residues at the amino-terminus were determined. These relatively large toxins (apparent molecular mass 73 kDa) were labile under many isolation techniques, but anion-exchange chromatography allowed purification with retention of biological activity. Two purified toxins were quite insecticidal (LD₅₀ < 0.3μg/g) when injected into six species of lepidopterous larvae. On a molar basis, one toxin (Brh-I) has the highest known biocidal activity against Heliothis virescens (LD₅₀ = 2 pmol/g).     

Studies on the status of tyrosyl residues in phospholipases A2 fromNaja naja atra andNaja nigricollis snake venoms

Two phospholipases A₂ (PLA₂) fromNaja naja atra andNaja nigricollis snake venoms were subjected to tyrosine modification withp-nitrobenzenesulfonyl fluoride (NBSF) atpH 8.0. Three major NBS derivatives from each PLA₂ were separated by high-performance liquid chromatography. The results of amino acid analysis showed that only two Tyr residues out of nine were modified, and the modified residues were identified to be Tyr-3 and Tyr-63 (or Tyr-62) in the sequence. Spectrophotometric titration indicated that the phenolic group of Tyr-3 and Tyr-63 (or Tyr-62) had apK of 10.1 and 11.0, respectively. The reactivity of Tyr-3 toward NBSF was not affected in the presence or absence of Ca²⁺; however, the reactivity of Tyr-63 (or Tyr-62) toward NBSF was greatly enhanced by Ca²⁺. Modification of Tyr-63 (or Tyr-62) resulted in a marked decrease in both lethality and enzymatic activity. Conversely, modification of Tyr-3 inN. naja atra PLA₂ could cause more than a sixfold increase in lethal potency, in sharp contrast to the loss of enzymatic activity.Tyrosine-63-modifiedN. naja atra PLA₂ exhibited the same Ca²⁺-induced difference spectra as that of native PLA₂, indicating that the Ca²⁺-binding ability of Tyr-63-modifiedN. naja atra PLA₂ was not impaired. However, Tyr-3-modified PLA₂ and all Tyr-modifiedN. nigricollis CMS-9 were not perturbed by Ca²⁺, revealing that the Ca²⁺-binding ability have been lost after tyrosine modification. These results suggest that Tyr-62 inN. nigricollis CMS-9 and Tyr-3 in both enzymes are involved in Ca²⁺ binding. AtpH 8.0, both native PLA₂ enzymes enhance the emission intensity of 8-anilinonaphthalene sulfonate (ANS) dramatically, while all of the Tyr-modified derivatives did not enhance the emission intensity at all either in the presence or absence of Ca²⁺, suggesting that the hydrophobic pocket that interacts with ANS might be the substrate binding site, in which Tyr-3 and Tyr-63 (or Tyr-62) are involved.     

Characterization of a highly stable trypsin-like proteinase inhibitor from the seeds of Opuntia streptacantha (O. streptacantha Lemaire)

A trypsin inhibitor from Opuntia streptacantha Lemaire (Prickly pear) seeds was purified and characterized. Of several proteases tested, this inhibitor showed specificity to trypsin-like enzymes. The major inhibitor present in these seeds showed distinctive characteristics, most notably a low molecular weight of 4.19 kDa, as determined by MALDI TOF, and an unusually high thermal stability, retaining most of the activity after heating the sample 1 h to 120 °C with a pressure of 1 kg/cm². Its complete amino acid sequence was obtained through mass spectrometry, this establishing presence a blocked N-terminal region. When comparing its sequence in the MEROPS database for peptidases and peptidase inhibitors, it showed 34.48% identity with a serine-proteinase inhibitor from the I15 family.