A lectin-like peptide isolated from the venom of the Chinese bird spider Selenocosmia huwena

Classes, Databases, and Prediction Methods of Pharmaceutically and Commercially Important Cystine-Stabilized Peptides

Cystine-stabilized peptides represent a large family of peptides characterized by high structural stability and bactericidal, fungicidal, or insecticidal properties. Found throughout a wide range of taxa, this broad and functionally important family can be subclassified into distinct groups dependent upon their number and type of cystine bonding patters, tertiary structures, and/or their species of origin. Furthermore, the annotation of proteins related to the cystine-stabilized family are under-represented in the literature due to their difficulty of isolation and identification. As a result, there are several recent attempts to collate them into data resources and build analytic tools for their dynamic prediction. Ultimately, the identification and delivery of new members of this family will lead to their growing inclusion into the repertoire of commercial viable alternatives to antibiotics and environmentally safe insecticides. This review of the literature and current state of cystine-stabilized peptide biology is aimed to better describe peptide subfamilies, identify databases and analytics resources associated with specific cystine-stabilized peptides, and highlight their current commercial success.

The Venom of Ornithoctonus huwena affect the electrophysiological stability of neonatal rat ventricular myocytes by inhibiting sodium, potassium and calcium current

Spider venoms are known to contain various toxins that are used as an effective means to capture their prey or to defend themselves against predators. An investigation of the properties of Ornithoctonus huwena (O.huwena) crude venom found that the venom can block neuromuscular transmission of isolated mouse phrenic nerve-diaphragm and sciatic nerve-sartorius preparations. However, little is known about its electrophysiological effects on cardiac myocytes. In this study, electrophysiological activities of ventricular myocytes were detected by 100 μg/mL venom of O.huwena, and whole cell patch-clamp technique was used to study the acute effects of the venom on action potential (AP), sodium current (I_Na), potassium currents (I_Kr, I_Ks, I_to1 and I_K1) and L-type calcium current (I_CaL). The results indicated that the venom prolongs APD₉₀ in a frequency-dependent manner in isolated neonatal rat ventricular myocytes. 100 μg/mL venom inhibited 72.3 ± 3.6% I_Na current, 58.3 ± 4.2% summit current and 54 ± 6.1% the end current of I_Kr, and 65 ± 3.3% I_CaL current, yet, didn't have obvious effect on I_Ks, I_to1 and I_K1 currents. In conclusion, the O.huwena venom represented a multifaceted pharmacological profile. It contains abundant of cardiac channel antagonists and might be valuable tools for investigation of both channels and anti- arrhythmic therapy development.

Molecular cloning and in silico characterization of knottin peptide, U2-SCRTX-Lit2, from brown spider (Loxosceles intermedia) venom glands

Inhibitor cystine knots (ICKs) are a family of structural peptides with a large number of cysteine residues that form intramolecular disulfide bonds, resulting in a knot. These peptides are involved in a variety of biological functions including predation and defense, and are found in various species, such as spiders, scorpions, sea anemones, and plants. The Loxosceles intermedia venom gland transcriptome identified five groups of ICK peptides that represent more than 50 % of toxin-coding transcripts. Here, we describe the molecular cloning of U2-Sicaritoxin-Lit2 (U2-SCRTX-Lit2), bioinformatic characterization, structure prediction, and molecular dynamic analysis. The sequence of U2-SCRTX-Lit2 obtained from the transcriptome is similar to that of μ-Hexatoxin-Mg2, a peptide that inhibits the insect Nav channel. Bioinformatic analysis of sequences classified as ICK family members also showed a conservation of cysteine residues among ICKs from different spiders, with the three dimensional molecular model of U2-SCRTX-Lit2 similar in structure to the hexatoxin from μ-hexatoxin-Mg2a. Molecular docking experiments showed the interaction of U2-SCRTX-Lit2 to its predictable target-the Spodoptera litura voltage-gated sodium channel (SlNaVSC). After 200 ns of molecular dynamic simulation, the final structure of the complex showed stability in agreement with the experimental data. The above analysis corroborates the existence of a peptide toxin with insecticidal activity from a novel ICK family in L. intermedia venom and demonstrates that this peptide targets Nav channels.

Molecular diversity of spider venom

Spider venom, a factor that has played a decisive role in the evolution of one of the most successful groups of living organisms, is reviewed. Unique molecular diversity of venom components including substances of variable structure (from simple low molecular weight compounds to large multidomain proteins) with different functions is considered. Special attention is given to the structure, properties, and biosynthesis of toxins of polypeptide nature.

Multivalent binding of carbohydrates by the human alpha-defensin, HD5

Four of the six human alpha-defensins (human neutrophil peptides 1-3 and human alpha-defensin 5; HD5) have a lectin-like ability to bind glycosylated proteins. Using HD5 as a model, we applied surface plasmon resonance techniques to gain insights into this property. HD5 bound natural glycoproteins > neoglycoproteins based on BSA > nonglycosylated BSA >> free sugars. The affinity of HD5 for simple sugars covalently bound to BSA was orders of magnitude greater than its affinity for the same sugars in solution. The affinity of HD5 for protein-bound carbohydrates resulted from multivalent interactions which may also involve noncarbohydrate residues of the proteins. HD5 showed concentration-dependent self-association that began at submicromolar concentrations and proceeded to dimer and tetramer formation at concentrations below 5 microM. The (R9A, R28A) and (R13A, R32A) analogs of HD5 showed greatly reduced self-association as well as minimal binding to BSA and to BSA-affixed sugars. From this and other evidence, we conclude that the extensive binding of HD5 to (neo)glycoproteins results from multivalent nonspecific interactions of individual HD5 molecules with carbohydrate and noncarbohydrate moieties of the target molecule and that the primary binding events are magnified and enhanced by subsequent in situ assembly and oligomerization of HD5. Self-association and multivalent binding may play integral roles in the ability of HD5 to protect against infections caused by viruses and other infectious agents.

Expression, purification and characterization of a group of lectin-like peptides from the spider Ornithoctonus huwena

By sequencing random clones from the venom gland cDNA library of the spider Ornithoctonus huwena, a transcript, named SHL-Ib1, encoding a lectin-like peptide was cloned. The amino acid sequence of the putative mature peptide of SHL-Ib1 is identical, except for seven different residues, with that of SHL-I, a lectin found in the venom of O. huwena. The mature peptides of SHL-Ib1b and SHL-Ib1c are the mutants of SHL-Ib1 with two or three amino acid residues truncated at the C-terminal. The recombinant SHL-Ib1b and SHL-Ib1c were expressed successfully by the yeast expression system and purified by using a combination of ion-exchange and reverse phase high performance liquid chromatography (HPLC). The molecular masses of the two expressed peptides were identified by mass spectrometry, indicating that the C-terminals of the two peptides were not amidated. The two peptides can agglutinate human erythrocytes at minimal concentrations of 0.75 and 1.475mg/ml, respectively. Structure modeling of SHL-Ib1 has given a clue to the low agglutination bioactivities of these recombinant toxins. These lectin-like peptides, due to the small molecular sizes, may have the advantage to investigate the binding mechanism of the lectin and have the potential to be the carrier for drug delivery.

Transcriptome analysis of Loxosceles laeta (Araneae, Sicariidae) spider venomous gland using expressed sequence tags

Background

The bite of spiders belonging to the genus Loxosceles can induce a variety of clinical symptoms, including dermonecrosis, thrombosis, vascular leakage, haemolysis, and persistent inflammation. In order to examine the transcripts expressed in venom gland of Loxosceles laeta spider and to unveil the potential of its products on cellular structure and functional aspects, we generated 3,008 expressed sequence tags (ESTs) from a cDNA library.

Results

All ESTs were clustered into 1,357 clusters, of which 16.4% of the total ESTs belong to recognized toxin-coding sequences, being the Sphingomyelinases D the most abundant transcript; 14.5% include "possible toxins", whose transcripts correspond to metalloproteinases, serinoproteinases, hyaluronidases, lipases, C-lectins, cystein peptidases and inhibitors. Thirty three percent of the ESTs are similar to cellular transcripts, being the major part represented by molecules involved in gene and protein expression, reflecting the specialization of this tissue for protein synthesis. In addition, a considerable number of sequences, 25%, has no significant similarity to any known sequence.

Conclusion

This study provides a first global view of the gene expression scenario of the venom gland of L. laeta described so far, indicating the molecular bases of its venom composition.

Proteomic and peptidomic characterization of the venom from the Chinese bird spider, Ornithoctonus huwena Wang

The bird spider Ornithoctonus huwena Wang is a very venomous spider in China. Several compounds with different types of biological activities have been identified previously from the venom of this spider. In this study, we have performed a proteomic and peptidomic analysis of the venom. The venom was preseparated into two parts: the venom proteins with molecular weight (MW) higher than 10,000 and the venom peptides with MW lower than 10 000. Using one-dimensional gel electrophoresis (1-DE), two-dimensional gel electrophoresis (2-DE), and mass spectrometry, 90 proteins were identified, including some important enzymes, binding proteins, and some proteins with significant biological functions. For venom peptides, a combination of cation-exchange and reversed-phase chromatography was employed. More than 100 components were detected by mass spectrometry, and 47 peptides were sequenced by Edman degradation. The peptides display structural and pharmacological diversity and share little sequence similarity with peptides from other animal venoms, which indicates the venom of O. huwena Wang is unique. The venom peptides can be classified into several superfamilies. Also it is revealed that gene duplication and focal hypermutation have taken place during the evolution of the spider toxins.

Proteomic and peptidomic analysis of the venom from Chinese tarantulaChilobrachys jingzhao

Chinese tarantula, Chilobrachys jingzhao is one of the most venomous spiders in southern China and its venom is a mixture of various compounds with diversified biological activities. The proteome of C. jingzhao venom was analyzed by proteomic techniques. Proteins with molecular weight of over 10 kDa, indicated by gel-filtration and SDS-PAGE, were analyzed using 2-DE and MALDI-TOF/TOF and LC/ESI-Q-TOF MS. More than 90 proteins were detected, with 47 confirmed by sequence similarity search using mass spectrum driven basic local alignment search tool (MS BLAST). On the other hand, peptides with MW lower than 10 kDa were separated by HPLC and identified by MALDI-TOF MS and Edman degradation sequencing. About 120 peptides were detected, 60 of which were fully or partially sequenced. Our results indicate that peptides with MW lower than 10 kDa are the major components in the crude venom of C. jingzhao. Like those of other tarantulas, these peptides are very likely to act on various ion channels. These results pave a way for further detailed structure-function correlation analysis of the individual toxins present in the venom of C. jingzhao.

Biological activities of a lectin from Bothrops jararacussu snake venom

Snake venoms contain saccharide-binding lectins. In this work, we examined the biological activities of a lectin (BjcuL) purified from Bothrops jararacussu snake venom by chromatography on non-derivatized Sepharose 4B and Sephacryl S-200 HR. The protein, a homodimer with subunits of 14.5 kDa, gave a single immunoprecipitin line in immunoelectrophoresis and cross-reacted in ELISA with antivenoms raised against Bothrops spp. (lanceheads), Micrurus spp. (coral snakes), Crotalus durissus terrificus (South American rattlesnake), and arthropod (Loxosceles gaucho, Phoneutria nigriventer and Tityus serrulatus) venoms. BjcuL agglutinated human formaldehyde-fixed erythrocytes at > or = 100 ng/ml and was inhibited by lactose and EDTA (> or = 2 mM) and high concentrations (> 100 mM) of glucose and sucrose, but not by N-acetylglucosamine. BjcuL had no direct hemolytic activity and was devoid of esterase, PLA2 and proteolytic activities. The lectin (up to 200 microg/ml) did not aggregate human platelet-rich plasma (PRP) or washed platelets (WP), nor did it alter the aggregation induced by ADP in PRP or by thrombin in WP. When injected into mouse hind paws, BjcuL (10-100 microg/paw) caused edema and increased vascular permeability, with a maximum effect after 1h that persisted for up to 6 h (edema) or gradually decreased after the peak interval (vascular permeability). No hemorrhage was observed in BjcuL-injected paws. In anesthetized rats, B. jararacussu venom (200 microg/kg, i.v.) produced sustained hypotension (maximum decrease of approximately 60%) whereas a similar dose of BjcuL decreased the blood pressure by approximately 15%, with a rapid return to the resting level.

Classification of spider neurotoxins using structural motifs by primary structure features. Single residue distribution analysis and pattern analysis techniques

In recent years the data on the novel structures of spider toxins have been greatly increasing. The sequence data should be classified. We introduced two primary structure analysis techniques-single residue distribution analysis (SRDA) and pattern analysis for classifying spider polypeptide toxins with molecular weight less than 10kDa. For multiple sequence alignment, we also introduced three novel sequence representation formats named as a simple record, motif record and a pattern record, which can be useful for large-scale analysis of structures. About 300 sequences of spider toxins were analyzed and nine primary structure motifs were identified. New classification of spider toxins was proposed on the basis of previously described principal structural motif (PSM) and extra structural motif (ESM) [Kozlov, S.A., Malyavka, A.A., McCutchen, B., Lu, A., Schepers, E., Herrmann, R., Grishin, E.V., 2005. A novel strategy for the identification of toxin-like structures in spider venom. Proteins 59 (1), 131-140]. Five main structural classes were revealed, and for putative ion channel inhibitors from the most numerous classes 1, 2, and 3, five-digital personal ID numbers were introduced. A reference table with simple, motif and pattern representation sequence formats was created for all analyzed structures.

An overview of peptide toxins from the venom of the Chinese bird spider Selenocosmia huwena Wang [=Ornithoctonus huwena (Wang)]

The bird spider Selenocosmia huwena Wang [=Ornithoctonus huwena (Wang)] is one of the most venomous spiders in China. The venom of this spider contains a mixture of compounds with different types of biological activity. About 400 proteins and peptides from the venom can be separated and detected by 2D electrophoresis. Of these, 14 peptide toxins have been purified and characterized from the venom of this spider, with several peptide toxins exhibiting structural similarity but high functional diversity. Most of these huwentoxins (HWTX) contain 30-40 amino acids with three disulfide bonds and adopt an "inhibitor cystine-knot" (ICK) motif in their three dimensional structure, except for huwentoxin-II (HWTX-II) which adopts a novel scaffold different from the ICK motif. As a group, the toxins possess quite different biological activities including inhibition of voltage-gated calcium and sodium channels, insecticidal activity, lectin-like agglutination, and inhibition of trypsin. Eight cDNAs encoding seven toxins, HWTX-I, -II, -III, -IIIa, -IV -V, and, -VII and one lectin, S. huwena lectin-I (SHL-I), have been cloned and sequenced. Comparison of the cDNA sequences of the eight peptides from S. huwena indicates that they can be classified into two different superfamilies according to the "prepro" region of their cDNA sequences.

Tarantulas: eight-legged pharmacists and combinatorial chemists

Tarantula venoms represent a cornucopia of novel ligands for a variety of cell receptors and ion channels. The diversity of peptide toxin pharmacology has been barely explored as indicated by pharmacological, toxicological and mass spectrometry investigations on more than 55 tarantula venoms. MALDI-TOF MS analysis reveals that the pharmacological diversity is based on relatively small size peptides, which seem to fall into a limited number of structural patterns. Properties and biological activities of the 33 known peptide toxins from tarantula venoms are described. Most known toxins conform to the Inhibitory Cystine Knot (ICK) motif, with differences in the length of intercysteine loops. Recently described peptides show that tarantula toxins can fold according to an elaboration of the Disulfide-Directed beta-Hairpin (DDH) motif which is also the canonical motif for the ICK fold. The ICK fold itself offers many variations leading to differing toxin properties. Examination of pharmacological data gives insights on the possible conserved site of action of toxins acting on voltage-gated ion channels and other toxins acting by a pore-blocking mechanism. Structure-activity data shows the versatility of the toxin scaffolds and the importance of surface features in the selectivity and specificity of these toxins. Tarantulas appear to be a good model for the discovery of novel compounds with important therapeutic potential, and for the study of the molecular evolution of peptide toxins.

cDNA sequence analysis of seven peptide toxins from the spider Selenocosmia huwena

Seven cDNAs encoding six toxins HWTX-I, HWTX-II, HWTX-IIIa, HWTX-IV, HWTX-V, HWTX-VII and one lectin SHL-I, from the spider Selenocosmia huwena, were cloned and sequenced. On the basis of their amino acid sequences, we designed and synthesized 3' RACE and 5' RACE primer. By overlapping the two partial cDNA sequences obtained by 3' and 5' RACE, their full-length cDNA sequences were obtained. All of the cDNAs of these seven peptides encode a precursor including a potential signal peptide of 21-24 residues, a mature toxin of about 30 residues and an intervening pro region. The prepro regions of HWTX-I, HWTX-IIIa, HWTX-IV, HWTX-V and SHL-I were demonstrated, by the comparison of the cDNA sequences, to have high similarity, which is concert with the similar inhibitor cystine knot motif of HWTX-I, HWTX-IV and SHL-I although their functions are different. It was also demonstrated that, HWTX-II and HWTX-VII share the highly similar prepro region which is different from that of HWTX-I, HWTX-IV and SHL-I. The three dimensional structure of HWTX-II has been determined to exhibit a different motif. This indicates that the seven peptides from S. huwena could be classified into two different superfamilies according to the prepro region of cDNA sequences.

Lebecetin, a potent antiplatelet C-type lectin from Macrovipera lebetina venom

A novel C-type lectin protein (CLP), lebecetin, was purified to homogeneity from the venom of Macrovipera lebetina by gel filtration on a Sephadex G75 column and ion exchange chromatography on Mono S column. Lebecetin is a basic protein with a pHi=9.9 and migrates in SDS-PAGE as a single band or two distinct bands under nonreducing and reducing conditions, respectively. These results are further confirmed by MALDI-TOF mass spectrometry that indicates a molecular mass of 29779 Da for native lebecetin and molecular masses of 15015 and 16296 Da for alpha and beta subunits, respectively. The N-terminal amino acid sequences of lebecetin subunits show a high degree of similarity with those of C-type lectin-like proteins. In addition, functional studies showed that lebecetin has a potent inhibitory effect on platelet aggregation induced by thrombin in a concentration-dependent manner. In contrast, no inhibitory effect is observed when platelets are exposed to thromboxane A2 (TxA2) mimetic (U46619) or arachidonic acid. Moreover, there was no effect either on blood coagulation or A, B and O washed human erythrocytes agglutination. Furthermore, flow cytometric analysis revealed that fluoro-isothiocyanate (FITC)-labelled lebecetin bound to human formalin fixed platelets in a saturable and concentration manner and this binding was specifically prevented by anti-glycoprotein Ib (GPIb) mAb. These observations suggest that lebecetin is a C-type lectin-like protein that selectively binds to platelet GPIb.

Huwentoxin-V, a novel insecticidal peptide toxin from the spider Selenocosmia huwena, and a natural mutant of the toxin: indicates the key amino acid residues related to the biological activity

A neurotoxin peptide (named Huwentoxin-V) was purified from the venom of the Chinese bird spider Selenocosmia huwena by a combination of ion exchange chromatography and reverse phase HPLC. HWTX-V has 35 amino acid residues, and is in perfect agreement with the molecular mass 4111.4 Da identified by mass spectrometry. A natural mutant of the toxin (called mHuwentoxin-V) was also isolated from the venom. mHWTX-V was only truncated two amino acid residues from the C-terminus of HWTX-V, and its molecular weight is 3877.1 Da determined by mass spectrometry. The six cysteine residues in each sequence of the two peptides suggest three disulfide bridges, the present of which was demonstrated by mass spectrometry after dithiothreiotol reduce and S-carboxymethylation. The primary structure of the two toxins exhibits sequence identity with other spider toxins such as ProTx-I (64%), SGTx (57%), SNX-482 (55%), and Hanatoxin (54%). HWTX-V can reversibly paralyze locusts and cockroaches for several hours with a ED50 value as 16 +/- 5 microg/g to locusts, and a larger dose of the toxin can cause death. However, mHWTX-V shows no significant effect on locusts and cockroaches. The structure-activity relationship indicates that the residues Phe34 and Ser35 in the C-terminus of HWTX-V are the key residues of the biological activity.

Purification and characterization of raventoxin-I and raventoxin-III, two neurotoxic peptides from the venom of the spider Macrothele raveni

The spider Macrothele raveni was recently identified as a new species of Genus Macrothele. The crude venom from M. raveni was found to be neurotoxic to mice and the LD(50) of the crude venom in mice was 2.852mg/kg. Two neurotoxic peptides, raventoxin-I and raventoxin-III, were isolated from the crude venom by ion-exchange and reverse phase high performance liquid chromatography. Raventoxin-I was the most abundant toxic component in the venom, while raventoxin-III was a lower abundant component. Both toxins can kill mice and block neuromuscular transmission in an isolated mouse phrenic nerve diaphragm preparation, but have no effect on cockroaches. The LD(50) of raventoxin-I in mice is 0.772mg/kg. The complete amino acid sequences of raventoxin-I and raventoxin-III were determined and found to consist of 43 and 29 amino acid residues, respectively. It was determined by mass spectrometry that all Cys residues from raventoxin-I and raventoxin-III are involved in disulphide bonds. raventoxin-III showed no significant sequence homology with any presently known neurotoxins in the protein/DNA databases, while raventoxin-I has limited sequence identity with delta-AcTx-Hv1 and delta-AcTx-Ar1, which target both mammalian and insect sodium channels. Both raventoxin-I and raventoxin-III only work on vertebrates, but not on insects. Moreover, raventoxin-I could exert an effect of first exciting and then inhibiting the contraction of mouse diaphragm muscle caused by electrically stimulating the phrenic nerve, but raventoxin-III could not.

Pharmacology and biochemistry of spider venoms

Spider venoms represent an incredible source of biologically active substances which selectively target a variety of vital physiological functions in both insects and mammals. Many toxins isolated from spider venoms have been invaluable in helping to determine the role and diversity of neuronal ion channels and the process of exocytosis. In addition, there is enormous potential for the use of insect specific toxins from animal sources in agriculture. For these reasons, the past 15-20 years has seen a dramatic increase in studies on the venoms of many animals, particularly scorpions and spiders. This review covers the pharmacological and biochemical activities of spider venoms and the nature of the active components. In particular, it focuses on the wide variety of ion channel toxins, novel non-neurotoxic peptide toxins, enzymes and low molecular weight compounds that have been isolated. It also discusses the intraspecific sex differences in given species of spiders.

Purification, structure determination and synthesis of covalitoxin-II, a short insect-specific neurotoxic peptide from the venom of the Coremiocnemis validus (Singapore tarantula)

Spider venoms contain toxins that specifically immobilize and kill insects. We report the purification and characterization of a new insect-specific toxin named covalitoxin-II (Cvtx-II; mass, 3406. 24+/-0.64), from Coremiocnemis validus (Singapore tarantula) venom. The complete 31 amino acid sequence of Cvtx-II has been determined and it shows less than 40% identity with spider toxins. However, Cvtx-II has conserved cystine motif analogous to other spider and omega-conotoxins. Cvtx-II was chemically synthesized and identified with the native Cvtx-II. Synthetic Cvtx-II induced insect-specific non-lethal excitatory activity when injected into crickets, but not in cockroaches and mice.

Indentification of venom proteins of spider S. huwena on two-dimensional electrophoresis gel by N-terminal microsequencing and mass spectrometric peptide mapping

Venom proteins of the spider Selenocosmia huwena were separated by two-dimensional gel electrophoresis, with the separation in the first dimension on a wide range of immobilized pH (3-10) gradients. Over 300 protein spots were presented on a silver-stained 2D gel. The protein spots with molecular weight >10 kDa were analyzed, after electrotransferring to polyvinyldene difluoride (PVDF) membrane, by N-terminal microseqencing. Some of the silver-stained protein spots with molecular weight over 10 kDa were analyzed and identified by employing an improved procedure of mass spectrometric peptide mapping, including (1) in-gel reduction, alkylation, and enzymatic digestion; (2) extraction and desalting by using the pipette tip containing a small C18 microcolumn (Ziptip); and (3) direct MAIDI-TOF mass analysis and protein database searching. Several known toxins such as HWTX-I, HWTX-II, HWTX-IV, and SHL-I were identified and some new components were found among these protein spots.

Three-dimensional structure of Selenocosmia huwena lectin-I (SHL-I) from the venom of the spider Selenocosmia huwena by 2D-NMR

The three-dimensional structure of native SHL-I, a lectin from the venom of the Chinese bird spider Selenocosmia huwena, has been determined from two-dimensional 1H NMR spectroscopy recorded at 500 and 600 MHz. The best 10 structures have NOE violation <0.3 A, dihedral violation <2 deg, and average root-mean-square differences of 0.85 + 0.06 A over backbone atoms. The structure consists of a three-stranded antiparallel beta-sheet and three turns. The three disulfide bridges and three-stranded antiparallel beta-sheet form a inhibitor cystine knot motif which is adopted by several other small proteins, such as huwentoxin-I, omega-conotoxin, and gurmarin. The C-terminal fragment from Leu28 to Trp32 adopts two sets of conformations corresponding to the cis and trans conformations of Pro31. The structure of SHL-I also has high similarity with that of the N-terminus of hevein, a lectin from rubber-tree latex.

Primary structure and biological activity of snake venom lectin (APL) from Agkistrodon p. piscivorus (Eastern cottonmouth)

A lectin (APL) was purified from the venom of Agkistrodon piscivorus piscivorus (Eastern cottonmouth moccasin). APL is a disulfide-linked, homodimeric protein consisting of identical monomers of molecular weight 16,200. Native rabbit and human erythrocytes were agglutinated by APL and the activity was found to be calcium-dependent. Galactose, lactose, rhamnose and EGTA strongly inhibited the hemagglutination activity of APL. The complete amino acid sequence determined by Edman sequencing of the S-pyridylethylated derivative and its peptides derived from enzymatic digestion indicate the structure of APL to be highly homologous with lectins and the platelet glycoprotein Ib (GPIb)-binding proteins isolated from other snake venoms. These results suggest that APL belongs to the C-type beta-galactoside binding lectin family which possess structural similarities with the C-terminal carbohydrate-recognition domain (CRD) of animal membrane lectins.

Purification and characterization of huwentoxin-II, a neurotoxic peptide from the venom of the Chinese bird spider Selenocosmia huwena

A neurotoxic peptide, huwentoxin-II (HWTX-II), was purified from the venom of the Chinese bird spider Selenocosmia huwena by ion exchange chromatography and reversed phase HPLC. The toxin can reversibly paralyse cockroaches for several hours, with an ED50 of 127 +/- 54 microg/g. HWTX-II blocks neuromuscular transmission in an isolated mouse phrenic nerve diaphragm preparation and acts cooperatively to potentiate the activity of huwentoxin-I. The complete amino sequence of HWTX-II was determined and found to consist of 37 amino acid residues, including six Cys residues. There is microheterogeneity (Ile/Gln) in position 10, and mass spectrometry indicated that the two isoproteins have a tendency to dimerize. It was determined by mass spectrometry that the six Cys residues are involved in three disulphide bonds. The sequence of HWTX-II is highly homologous with ESTX, a toxin from the tarantula Eurypefina californicum.

Assignment of the three disulfide bonds of Selenocosmia huwena lectin-I from the venom of spider Selenocosmia huwena

The positions of the disulfide bonds of Selenocosmia huwena lectin-I (SHL-I) from the venom of the Chinese bird spider S. huwena have been determined. The existence of three disulfide bonds in the native SHL-I was proved by matrix-assisted laser desorption ionization time-of-flight mass spectroscopic analysis. To map the disulfide bonds, native SHL-I was proteolytically digested. The resulting peptides were separated by reverse phase high-performance liquid chromatography. Matrix-assisted laser desorption ionization time-of-flight mass spectroscopic analysis indicated the presence of one disulfide bond Cys7-Cys19. The partially reduced peptides by using Tris-(2-carboxyethyl)-phosphine at pH 3.0 were purified by reverse phase high-performance liquid chromatography. Four M Guanidine-HCl was found to increase the yields of partially reduced peptides prominently. The free thiols were carboxamidomethlate by iodoacetamide. The specific location of another disulfide bond Cys2-Cys14 was proved by comparing N-terminal sequencing analysis of the partially reduced and alkylated SHL-I with that of the intact peptide. Finally, the three disulfide linkage of SHL-I could be assigned as Cys2-Cys14, Cys7-Cys19, Cys13-Cys26.