The scorpion toxin BeKm-1 blocks hERG cardiac potassium channels using an indispensable arginine residue

BeKm-1 is a peptide toxin from scorpion venom that blocks the pore of the potassium channel hERG (Kv11.1) in the human heart. Although individual protein structures have been resolved, the structure of the complex between hERG and BeKm-1 is unknown. Here, we used molecular dynamics and ensemble docking, guided by previous double-mutant cycle analysis data, to obtain an in silico model of the hERG-BeKm-1 complex. Adding to the previous mutagenesis study of BeKm-1, our model uncovers the key role of residue Arg20, which forms three interactions (a salt bridge and hydrogen bonds) with the channel vestibule simultaneously. Replacement of this residue even by lysine weakens the interactions significantly. In accordance, the recombinantly produced BeKm-1R20K mutant exhibited dramatically decreased activity on hERG. Our model may be useful for future drug design attempts.

Divergence in toxin antigenicity and venom enzymes in Tityus melici, a medically important scorpion, despite transcriptomic and phylogenetic affinities with problematic Brazilian species

The Brazilian scorpion Tityus melici, native to Minas Gerais and Bahia, is morphologically related to Tityus serrulatus, the most medically significant species in Brazil. Despite inhabiting scorpion-envenomation endemic regions, T. melici venom remains unexplored. This work evaluates T. melici venom composition and function using transcriptomics, enzymatic activities, and in vivo and in vitro immunological analyses. Next-Generation Sequencing unveiled 86 components putatively involved in venom toxicity: 39 toxins, 28 metalloproteases, seven disulfide isomerases, six hyaluronidases, three phospholipases and three amidating enzymes. T. serrulatus showed the highest number of toxin matches with 80-100 % sequence similarity. T. melici is of medical importance as it has a venom LD50 of 0.85 mg/kg in mice. We demonstrated venom phospholipase A2 activity, and elevated hyaluronidase and metalloprotease activities compared to T. serrulatus, paralleling our transcriptomic findings. Comparison of transcriptional levels for T. serrulatus and T. melici venom metalloenzymes suggests species-specific expression patterns in Tityus. Despite close phylogenetic association with T. serrulatus inferred from COI sequences and toxin similarities, partial neutralization of T. melici venom toxicity was achieved when using the anti-T. serrulatus antivenom, implying antigenic divergence among their toxins. We suggest that the Brazilian therapeutic scorpion antivenom could be improved to effectively neutralize T. melici venom.

Genome-wide identification, structural homology analysis, and evolutionary diversification of the phospholipase D gene family in the venom gland of three scorpion species

BACKGROUND

Venom phospholipase D (PLDs), dermonecrotic toxins like, are the major molecules in the crude venom of scorpions, which are mainly responsible for lethality and dermonecrotic lesions during scorpion envenoming. The purpose of this study was fivefold: First, to identify transcripts coding for venom PLDs by transcriptomic analysis of the venom glands from Androctonus crassicauda, Hottentotta saulcyi, and Hemiscorpius lepturus; second, to classify them by sequence similarity to known PLDs and motif extraction method; third, to characterize scorpion PLDs; fourth to structural homology analysis with known dermonecrotic toxins; and fifth to investigate phylogenetic relationships of the PLD proteins.

RESULTS

We found that the venom gland of scorpions encodes two PLD isoforms: PLD1 ScoTox-beta and PLD2 ScoTox-alpha I. Two highly conserved regions shared by all PLD1s beta are GAN and HPCDC (HX2PCDC), and the most important conserved regions shared by all PLD2s alpha are two copies of the HKDG (HxKx4Dx6G) motif. We found that PLD1 beta is a 31-43 kDa acidic protein containing signal sequences, and PLD2 alpha is a 128 kDa basic protein without known signal sequences. The gene structures of PLD1 beta and PLD2 alpha contain 6 and 21 exons, respectively. Significant structural homology and similarities were found between the modeled PLD1 ScoTox-beta and the crystal structure of dermonecrotic toxins from Loxosceles intermedia.

CONCLUSIONS

This is the first report on identifying PLDs from A. crassicauda and H. saulcyi venom glands. Our work provides valuable insights into the diversity of scorpion PLD genes and could be helpful in future studies on recombinant antivenoms production.

Identification, Characterization, and Modeling of a Bioinsecticide Protein Isolated from Scorpion Venom gland: A Three-Finger Protein

Background

The majority of insecticides target sodium channels. The increasing emergence of resistance to the current insecticides has persuaded researchers to search for alternative compounds. Scorpion venom gland as a reservoir of peptides or proteins, which selectively target insect sodium channels. These proteins would be an appropriate source for finding new suitable anti-insect components.

Methods

Transcriptome of venom gland of scorpion Mesobuthus eupeus was obtained by RNA extraction and complementary DNA library synthesis. The obtained transcriptome was blasted against protein databases to find insect toxins against sodium channel based on the statistically significant similarity in sequence. Physicochemical properties of the identified protein were calculated using bioinformatics software. The three-dimensional structure of this protein was determined using homology modeling, and the final structure was assessed by molecular dynamics simulation.

Results

The sodium channel blocker found in the transcriptome of M. eupeus venom gland was submitted to the GenBank under the name of meuNa10, a stable hydrophilic protein consisting of 69 amino acids, with the molecular weight of 7721.77 g/mol and pI of 8.7. The tertiary structure of meuNa10 revealed a conserved LCN-type cysteine-stabilized alpha/beta domain stabilized by eight cysteine residues. The meuNa10 is a member of the 3FP superfamily consisting of three finger-like beta strands.

Conclusion

This study identified meuNa10 as a small insect sodium channel-interacting protein with some physicochemical properties, including stability and water-solubility, which make it a good candidate for further in vivo and in vitro experiments in order to develop a new bioinsecticide.

Identification, Characterization, and Modeling of a Bioinsecticide Protein Isolated from Scorpion Venom gland: A Three-Finger Protein

Background

The majority of insecticides target sodium channels. The increasing emergence of resistance to the current insecticides has persuaded researchers to search for alternative compounds. Scorpion venom gland as a reservoir of peptides or proteins, which selectively target insect sodium channels. These proteins would be an appropriate source for finding new suitable anti-insect components.

Methods

Transcriptome of venom gland of scorpion Mesobuthus eupeus was obtained by RNA extraction and complementary DNA library synthesis. The obtained transcriptome was blasted against protein databases to find insect toxins against sodium channel based on the statistically significant similarity in sequence. Physicochemical properties of the identified protein were calculated using bioinformatics software. The three-dimensional structure of this protein was determined using homology modeling, and the final structure was assessed by molecular dynamics simulation.

Results

The sodium channel blocker found in the transcriptome of M. eupeus venom gland was submitted to the GenBank under the name of meuNa10, a stable hydrophilic protein consisting of 69 amino acids, with the molecular weight of 7721.77 g/mol and pI of 8.7. The tertiary structure of meuNa10 revealed a conserved LCN-type cysteine-stabilized alpha/beta domain stabilized by eight cysteine residues. The meuNa10 is a member of the 3FP superfamily consisting of three finger-like beta strands.

Conclusion

This study identified meuNa10 as a small insect sodium channel-interacting protein with some physicochemical properties, including stability and water-solubility, which make it a good candidate for further in vivo and in vitro experiments in order to develop a new bioinsecticide.

A first molecular characterization of the scorpion telson microbiota of Hadrurus arizonensis and Smeringurus mesaensis

Scorpions represent an ancient lineage of arachnids that have radiated across the globe and are incredibly resilient-since some thrive in harsh environments and can exist on minimal and intermittent feedings. Given the emerging importance of microbiomes to an organism's health, it is intriguing to suggest that the long-term success of the scorpion bauplan may be linked to the microbiome. Little is known about scorpion microbiomes, and what is known, concentrates on the gut. The microbiome is not limited to the gut, rather it can be found within tissues, fluids and on external surfaces. We tested whether the scorpion telson, the venom-producing organ, of two species, Smeringurus mesaensis and Hadrurus arizonensis, contain bacteria. We isolated telson DNA from each species, amplified bacterial 16S rRNA genes, and identified the collection of bacteria present within each scorpion species. Our results show for the first time that telsons of non-buthid scorpion species do indeed contain bacteria. Interestingly, each scorpion species has a phylogenetically unique telson microbiome including Mollicutes symbionts. This study may change how we view scorpion biology and their venoms.

A non-lethal method for studying scorpion venom gland transcriptomes, with a review of potentially suitable taxa to which it can be applied

Scorpion venoms are mixtures of proteins, peptides and small molecular compounds with high specificity for ion channels and are therefore considered to be promising candidates in the venoms-to-drugs pipeline. Transcriptomes are important tools for studying the composition and expression of scorpion venom. Unfortunately, studying the venom gland transcriptome traditionally requires sacrificing the animal and therefore is always a single snapshot in time. This paper describes a new way of generating a scorpion venom gland transcriptome without sacrificing the animal, thereby allowing the study of the transcriptome at various time points within a single individual. By comparing these venom-derived transcriptomes to the traditional whole-telson transcriptomes we show that the relative expression levels of the major toxin classes are similar. We further performed a multi-day extraction using our proposed method to show the possibility of doing a multiple time point transcriptome analysis. This allows for the study of patterns of toxin gene activation over time a single individual, and allows assessment of the effects of diet, season and other factors that are known or likely to influence intraindividual venom composition. We discuss the gland characteristics that may allow this method to be successful in scorpions and provide a review of other venomous taxa to which this method may potentially be successfully applied.

Expression and purification of recombinant alpha-toxin AnCra1 from the scorpion Androctonus crassicauda and its functional characterization on mammalian sodium channels

BACKGROUND

Alpha-scorpion toxins with long-chain peptide and four disulfide bonds represent diverse pharmacological profiles for various subtypes of voltage-gated sodium channels. Obtaining the natural toxins are difficult and time-consuming process, which represents the major difficulty to interpreting analysis of their structural and functional properties.

METHODS AND RESULTS

This study describes the toxin peptide and plasmid construct containing the gene coding for mammalian toxin AnCra1 from the scorpion Androctonus crassicauda venom. We have established genetic construction of fusion protein in pET32a + vector containing thioredoxin (Trx-tag), enterokinase cleavage site and 6xhistidine-tag for efficient expression in Escherichia coli strain RG2 (DE3). The soluble expressed peptide, then purified by Ni-NTA resin affinity chromatography and its purity was confirmed by reverse-phase HPLC and mass spectrometry (7433.54 Da.). The electrophysiological data showed that recombinant AnCra1 selectively inhibits the fast inactivation of hNav1.7 channel (EC₅₀ = 136.7 ± 6.6 nM).

CONCLUSIONS

Our findings demonstrate that the AnCra1 is structurally and functionally analogous to alpha excitatory toxins; furthermore, expression and purification of bioactive scorpion toxins in bacterial cells can be a practicable and efficient way to obtain a novel source of toxin peptides as tools to study the function and physiological responses of ion channels.

NMR three-dimensional structure of the cationic peptide Stigmurin from Tityus stigmurus scorpion venom: In vitro antioxidant and in vivo antibacterial and healing activity

Infectious diseases and the rapid development of pathogens resistant to conventional drugs are a serious global public health problem, which motivates the search for new pharmacological agents. In this context, cationic peptides without disulfide bridges from different species of scorpion venom have been the target of scientific studies due to their multifunctional activities. Stigmurin is a linear peptide composed of 17 amino acid residues (Phe-Phe-Ser-Leu-Ile-Pro-Ser-Leu-Val-Gly-Gly-Leu-Ile-Ser-Ala-Phe-Lys-NH₂), which is present in the venom gland of the scorpion Tityus stigmurus. Here we present investigations of the in vitro antioxidant action of Stigmurin together with the in vivo antibacterial and healing activity of this peptide in a wound infection model induced by Staphylococcus aureus. In addition, we have reports for the first time of the three-dimensional structure determined by NMR spectroscopy of a peptide without disulfide bridges present in scorpion venom from the Tityus genus. Stigmurin showed hydroxyl radical scavenging above 70 % at 10 μM and antibiotic action in the skin wound, reducing the number of viable microorganisms by 67.2 % on the 7 day after infection. Stigmurin (1 μg / μL) increased the retraction rate of the lesion, with wound area reduction of 43 % on the second day after skin injury, which indicates its ability to induce tissue repair. Stigmurin in trifluoroethanol:water exhibited a random conformation at the N-terminus region (Phe1 to Pro6), with a helical structure from Ser7 to Phe16. This structural information, allied with the multifunctional activity of Stigmurin, makes it an attractive candidate for the design of novel therapeutic agents.

De novo transcriptomic and proteomic analysis and potential toxin screening of Mesobuthus martensii samples from four different provinces

ETHNOPHARMACOLOGICAL RELEVANCE

As well-known medicinal materials in traditional Chinese medicine, scorpions, commonly called as Quanxie () in Chinese, have been widely used to treat several diseases such as rheumatoid arthritis, apoplexy, epilepsy and chronic pain for more than a thousand years. Not only in the ancient times, the scorpions have also been recorded nowadays in the Pharmacopoeia of the People's Republic of China since 1963.

AIM OF STUDY

This study aims to explore the differences in composition of the venom of scorpions from different regions by using the method of transcriptomics and proteomics.

MATERIALS AND METHODS

Whole de novo transcriptomes, proteomics and their bioinformatic analyses were performed on samples of the scorpion Mesobuthus martensii and their venoms from four different provinces with clear geographical boundaries, including Hebei, Henan, Shandong and Shanxi.

RESULTS

The four captured samples had the same morphology, and the conserved CO-1 sequence matched that of M. martensii. A total of 141,003 of 174,653 transcripts were identified as unigenes, of which we successfully annotated 51,627 (36.61%), 21,970 (15.58%), 7,168 (5.08%), and 45,263 (32.10%) unigenes with the NR, GO, KEGG and SWISSPROT databases, respectively, while a total of 427 proteins were collected from the protein extracted from venoms. Both GO and KEGG annotations exhibited only slight differences among the four samples while the expression level of gene and protein was quite different. A total of 249 toxin-related unigenes were successfully screened, including 41 serine proteases and serine protease inhibitors, 39 potassium channel toxins, 38 phospholipases, 16 host defense peptides, 9 metalloproteases, and 50 other toxins. Although the toxin species were similar among the four samples, the gene expression of each toxin varied considerably, for example, the scorpion from HB province has the most abundant expression quality in sequences c48391_g1, c55239_g1 and c47749_g1 while the lowest expressions of c51178_g1, c62033_g3 and c63754_g2.

CONCLUSION

The regional differences in the transcriptomes and proteomes of M. martensii are mainly from expression levels e.g. toxins rather than expression species, of which the method can be further extended to evaluate the qualities of traditional Chinese medicines obtained from different regions.

Synthesis and Biological Activity of Scyllatoxin-Based BH3 Domain Mimetics Containing Two Disulfide Linkages

The B cell lymphoma 2 (BCL2) proteins are a family of evolutionarily related proteins that act as positive or negative regulators of the intrinsic apoptosis pathway. Overexpression of anti-apoptotic BCL2 proteins in cells is associated with apoptotic resistance, which can result in cancerous phenotypes and pathogenic cell survival. Consequently, anti-apoptotic BCL2 proteins have attracted considerable interest as therapeutic targets. We recently reported the development of a novel class of synthetic protein based on scyllatoxin (ScTx) designed to mimic the helical BH3 interaction domain of the pro-apoptotic BCL2 protein Bax. These studies showed that the number and position of native disulfide linkages contained within the ScTx-Bax structure significantly influences the ability for these constructs to target anti-apoptotic BCL2 proteins in vitro. The goal of the present study is to investigate the contribution of two disulfide linkages in the folding and biological activity of ScTx-Bax proteins. Here, we report the full chemical synthesis of three ScTx-Bax sequence variants, each presenting two native disulfide linkages at different positions within the folded structure. It was observed that two disulfide linkages were sufficient to fold ScTx-Bax proteins into native-like architectures reminiscent of wild-type ScTx. Furthermore, we show that select (bis)disulfide ScTx-Bax variants can target Bcl-2 (proper) in vitro and that the position of the disulfide bonds significantly influences binding affinity. Despite exhibiting only modest binding to Bcl-2, the successful synthesis of ScTx-Bax proteins containing two disulfide linkages represents a viable route to ScTx-based BH3 domain mimetics that preserve native-like conformations. Finally, structural models of ScTx-Bax proteins in complex with Bcl-2 indicate that these helical mimetics bind in similar configurations as wild-type Bax BH3 domains. Taken together, these results suggest that ScTx-Bax proteins may serve as potent lead compounds that expand the repertoire of "druggable" protein-protein interactions.

Proteomic endorsed transcriptomic profiles of venom glands from Tityus obscurus and T. serrulatus scorpions

Background

Except for the northern region, where the Amazonian black scorpion, T. obscurus, represents the predominant and most medically relevant scorpion species, Tityus serrulatus, the Brazilian yellow scorpion, is widely distributed throughout Brazil, causing most envenoming and fatalities due to scorpion sting. In order to evaluate and compare the diversity of venom components of Tityus obscurus and T. serrulatus, we performed a transcriptomic investigation of the telsons (venom glands) corroborated by a shotgun proteomic analysis of the venom from the two species.

Results

The putative venom components represented 11.4% and 16.7% of the total gene expression for T. obscurus and T. serrulatus, respectively. Transcriptome and proteome data revealed high abundance of metalloproteinases sequences followed by sodium and potassium channel toxins, making the toxin core of the venom. The phylogenetic analysis of metalloproteinases from T. obscurus and T. serrulatus suggested an intraspecific gene expansion, as we previously observed for T. bahiensis, indicating that this enzyme may be under evolutionary pressure for diversification. We also identified several putative venom components such as anionic peptides, antimicrobial peptides, bradykinin-potentiating peptide, cysteine rich protein, serine proteinases, cathepsins, angiotensin-converting enzyme, endothelin-converting enzyme and chymotrypsin like protein, proteinases inhibitors, phospholipases and hyaluronidases.

Conclusion

The present work shows that the venom composition of these two allopatric species of Tityus are considerably similar in terms of the major classes of proteins produced and secreted, although their individual toxin sequences are considerably divergent. These differences at amino acid level may reflect in different epitopes for the same protein classes in each species, explaining the basis for the poor recognition of T. obscurus venom by the antiserum raised against other species.

Scorpion envenoming in Morona Santiago, Amazonian Ecuador: Molecular phylogenetics confirms involvement of the Tityus obscurus group

Scorpion envenoming by species in the genus Tityus is hereby reported from rural locations in the Amazonian province of Morona Santiago, southeastern Ecuador. Twenty envenoming cases (18 patients under 15 years of age) including one death (a 4-year-old male) were recorded at the Macas General Hospital, Morona Santiago, between January 2015 and December 2016 from the counties of Taisha (n=17), Huamboyo (n=1), Palora (n=1), and Logroño (n=1). An additional fatality from 2014 (a 3-year-old female from Nayantza, Taisha county) is also reported. Leukocytosis and low serum potassium levels were detected in most patients. We observed a significant negative correlation between leukocytosis and hypokalemia. Scorpions involved in three accidents from Macuma, Taisha County, were identified as genetically related to Tityus obscurus from the Brazilian Amazonian region based on comparison of mitochondrial DNA sequences encoding cytochrome oxidase subunit I. These cases, along with previously reported envenoming from northern Manabí, reinforce the notion that scorpionism is a health hazard for children in Ecuador and emphasizes the need to supply effective antivenoms against local species, which are not currently available. The genetic affinity of the Ecuadorian specimens with T. obscurus may underlay toxinological, clinical, and venom antigenic relationships among Amazonian scorpions that deserves further exploration for designing therapeutic strategies to treat scorpionism in the region.

Expression of recombinant α-toxin BmKM9 from scorpion Buthus martensii Karsch and its functional characterization on sodium channels

Scorpion toxins are invaluable pharmacological tools for studying ion channels and potential drugs for channelopathies. The long-chain toxins from scorpion venom with four disulfide bridges exhibit their unusual bioactivity or biotoxicity by acting on the sodium channels. However, the functional properties of most toxins are still unclear due to their tiny amounts in crude venom and their challenging production by chemical and gene engineering techniques. Here, we expressed one of the long-chain α-toxins, BmKM9, found in the venom of the scorpion Buthus martensii Karsch and characterized its pharmacological properties on sodium channels. Unlike previous toxin production, the recombinant BmKM9 (rBmKM9) possessed no additional amino acid residues such as the His-tag and thrombin cleavage site. The refolded toxin could inhibit the inactivation of rNa_v1.4, hNa_v1.5 and hNa_v1.7 sodium channels. Dose-response experiments were further conducted on these channels. The calculated EC₅₀ values were 131.7±6.6nM for rNa_v1.4, 454.2±50.1nM for hNa_v1.5 and 30.9±10.3μM for hNa_v1.7. The channel activation experiments indicated that the rBmKM9 toxin could shift the activation curves of rNa_v1.4 and hNa_v1.5 channels toward a more negative direction and present the typical features of a β-toxin. However, instead of the same activation property on sodium channels, the rBmKM9 toxin could result in different inactivation shift capabilities on rNa_v1.4 and hNa_v1.5 channels. The V_1/2 values of the steady-state inactivation were altered to be more positive for rNa_v1.4 and more negative for hNa_v1.5. Moreover, the recovery of the hNa_v1.5 channel from inactivation was more significantly delayed than that of the rNa_v1.4 channel by exposure to rBmKM9. Together, these findings highlighted that the rBmKM9 toxin presents the pharmacological properties of both α- and β-toxins, which would increase the challenge to the classical classification of scorpion toxins. Furthermore, the expression method and functional information on sodium channels would promote the potential application of toxins and contribute to further channel structural and functional studies.

A Deeper Examination of Thorellius atrox Scorpion Venom Components with Omic Techonologies

This communication reports a further examination of venom gland transcripts and venom composition of the Mexican scorpion Thorellius atrox using RNA-seq and tandem mass spectrometry. The RNA-seq, which was performed with the Illumina protocol, yielded more than 20,000 assembled transcripts. Following a database search and annotation strategy, 160 transcripts were identified, potentially coding for venom components. A novel sequence was identified that potentially codes for a peptide with similarity to spider ω-agatoxins, which act on voltage-gated calcium channels, not known before to exist in scorpion venoms. Analogous transcripts were found in other scorpion species. They could represent members of a new scorpion toxin family, here named omegascorpins. The mass fingerprint by LC-MS identified 135 individual venom components, five of which matched with the theoretical masses of putative peptides translated from the transcriptome. The LC-MS/MS de novo sequencing allowed to reconstruct and identify 42 proteins encoded by assembled transcripts, thus validating the transcriptome analysis. Earlier studies conducted with this scorpion venom permitted the identification of only twenty putative venom components. The present work performed with more powerful and modern omic technologies demonstrates the capacity of accomplishing a deeper characterization of scorpion venom components and the identification of novel molecules with potential applications in biomedicine and the study of ion channel physiology.

Differential toxicity and venom gland gene expression in Centruroides vittatus

Variation in venom toxicity and composition exists in many species. In this study, venom potency and venom gland gene expression was evaluated in Centruroides vittatus, size class I-II (immature) and size class IV (adults/penultimate instars) size classes. Venom toxicity was evaluated by probit analysis and returned ED₅₀ values of 50.1 μg/g for class IV compared to 134.2 μg/g for class I-II 24 hours post injection, suggesting size class IV was 2.7 fold more potent. Next generation sequencing (NGS and qPCR were used to characterize venom gland gene expression. NGS data was assembled into 36,795 contigs, and annotated using BLASTx with UNIPROT. EdgeR analysis of the sequences showed statistically significant differential expression in transcripts associated with sodium and potassium channel modulation. Sodium channel modulator expression generally favored size class IV; in contrast, potassium channel modulators were favored in size class I-II expression. Real-time quantitative PCR of 14 venom toxin transcripts detected relative expression ratios that paralleled NGS data and identified potential family members or splice variants for several sodium channel modulators. Our data suggests ontogenetic differences in venom potency and venom related genes expression exist between size classes I-II and IV.

A bimodal activation mechanism underlies scorpion toxin-induced pain

Venomous animals use peptide toxins for hunting and self-defense. To achieve these goals, toxins need to bind to their targets with high affinity due to the small amount that a single bite or sting can deliver. The scorpion toxin BmP01 is linked to sting-induced excruciating pain; however, the reported minimum concentrations for activating TRPV1 channel or inhibiting voltage-gated potassium (Kv) channels (both in the micromolar range) appear too high to be biologically relevant. We show that the effective concentration of BmP01 is highly pH-dependent-it increases by about 10-fold in inhibiting Kv channels upon a 1-U drop in pH but decreases more than 100-fold in activating TRPV1. Mechanistic investigation revealed that BmP01 binds to one of the two proton-binding sites on TRPV1 and, together with a proton, uses a one-two punch approach to strongly activate the nociceptive channel. Because most animal venoms are acidic, proton-facilitated synergistic action may represent a general strategy for maximizing toxin potency.

Adaptive evolution of insect selective excitatory β-type sodium channel neurotoxins from scorpion venom

Insect selective excitatory β-type sodium channel neurotoxins from scorpion venom (β-NaScTxs) are composed of about 70-76 amino acid residues and share a common scaffold stabilized by four unique disulfide bonds. The phylogenetic analysis of these toxins was hindered by limited sequence data. In our recent study, two new insect selective excitatory β-NaScTxs, LmIT and ImIT, were isolated from Lychas mucronatus and Isometrus maculatus, respectively. With the sequences previously reported, we examined the adaptive molecular evolution of insect selective excitatory β-NaScTxs by estimating the nonsynonymous-to-synonymous rate ratio (ω=d_N/d_S). The results revealed 12 positively selected sites in the genes of insect selective excitatory β-NaScTxs. Moreover, these positively selected sites match well with the sites important for interacting with sodium channels, as demonstrated in previous mutagenesis study. These results reveal that adaptive evolution after gene duplication is one of the most important genetic mechanisms of scorpion neurotoxin diversification.

Discovery of three toxin peptides with Kv1.3 channel and IL-2 cytokine-inhibiting activities from Non-Buthidae scorpions, Chaerilus tricostatus and Chaerilus tryznai

Non-Buthidae venomous scorpions are huge natural sources of toxin peptides; however, only a few studies have been done to understand their toxin peptides. Herein, we describe three new potential immunomodulating toxin peptides, Ctri18, Ctry68 and Ctry2908, from two non-Buthidae scorpions, Chaerilus tricostatus and Chaerilus tryznai. Sequence alignment analyses showed that Ctri18, Ctry68 and Ctry2908 are three new members of the scorpion toxin α-KTx15 subfamily. Electrophysiological experiments showed that Ctri18, Ctry68 and Ctry2908 blocked the Kv1.3 channel at micromole to nanomole levels, but had weak effects on potassium channel KCNQ1 and sodium channel Nav1.4, which indicated that Ctri18, Ctry68 and Ctry2908 might have specific inhibiting effects on the Kv1.3 channel. ELISA experiments showed that Ctri18, Ctry68 and Ctry2908 inhibited IL-2 cytokine secretions of activated T lymphocyte in human PBMCs. Excitingly, consistent with the good Kv1.3 channel inhibitory activity, Ctry2908 inhibited cytokine IL-2 secretion in nanomole level, which indicated that Ctry2908 might be a new lead drug template toward Kv1.3 channels. Together, these studies discovered three new toxin peptides, Ctri18, Ctry68 and Ctry2908, with Kv1.3 channel and IL-2 cytokine-inhibiting activities from two scorpions, C. tricostatus and C. tryznai, and highlighted that non-Buthidae venomous scorpions are new natural toxin peptide sources.

A Novel Defensin-Like Peptide Associated with Two Other New Cationic Antimicrobial Peptides in Transcriptome of the Iranian Scorpion Venom

INTRODUCTION

Scorpion venom is a source of bioactive peptides, and some antimicrobial peptides (AMPs) have been found in the venom gland of scorpions. Therefore, the discovery of new anti-infective agents is an essential need to overcome the problem of antibiotic resistance of clinical isolates. Here, we describe three new cationic AMPs, including meuVAP-6, meuAP-18-1, and meuPep34 from the venom gland of the Iranian scorpion, Mesobuthus eupeus.

METHODS

The cDNA sequences encoding all the three peptides were obtained from the cDNA library of scorpion venom gland and were deposited in the GenBank database.

RESULTS

MeuVAP-6 and meuAP-18-1 are non-disulphide-bridged antimicrobial peptides, while meuPep34 is a cysteine-rich defensin-like peptide.

DISCUSSION

All three identified AMPs are rich in arginine and tryptophan. The overall results from the length, net charge, and hydrophobicity index suggested that meuPep34 could be the most active AMPs with the potential ability of biofilm inhibition. The data from molecular characterization of identified AMPs can provide a platform for further investigations in the drug design.

Feeding recombinant E. coli with GST-mBmKTX fusion protein increases the fecundity and lifespan of Caenorhabditis elegans

Scorpion venom could be a useful treatment for a variety of diseases, such as cancer, epilepsy and analgesia. BmKTX is a polypeptide extracts from scorpion venom (PESV), which have attracted much attention from researchers in recent years. mBmKTX is a mutant polypeptide according to the amino acid sequence of BmKTX. We expressed it with the vector pGEX-4T-1 in Escherichia coli, and Caenorhabditis elegans were used as the animal model and fed with the strains. In this study, the expression of pGEX-mBmKTX was analyzed by SDS-PAGE, and GST-mBmKTX purified from pGEX-mBmKTX as a glutathione S-transferase (GST)-tagged fusion protein is approximately 30kDa. The secondary structure prediction shows that mBmKTX is mainly composed of approximately 13% β-sheet and 86% loop. A food clearance assay and brood size assay indicated that the worms fed pGEX-mBmKTX ate more and had greater fecundity than those fed the empty vector. A lifespan analysis demonstrated that mBmKTX could significantly prolong the lifespan of C. elegans, with an increase of 22.5% compared with the control. Behavioral assays confirmed that mBmKTX had no influence on the locomotion of C. elegans. In addition, microarray analysis and quantitative real-time PCR demonstrated that there are 320 differentially expressed genes, 182 of which are related to reproduction, growth and lifespan. In conclusion, the data suggested that mBmKTX has potential utility for increasing fecundity and animal survival.

Bioactivity of Natural and Engineered Antimicrobial Peptides from Venom of the Scorpions Urodacus yaschenkoi and U. manicatus

The spread of multidrug-resistant human pathogens has drawn attention towards antimicrobial peptides (AMPs), which are major players in the innate immune systems of many organisms, including vertebrates, invertebrates, plants and microbes. Scorpion venom is an abundant source of novel and potent AMPs. Here, we investigated natural and engineered AMPs from the scorpions Urodacus yaschenkoi and U. manicatus to determine their antimicrobial spectra as well as their hemolytic/cytotoxic activity. None of the AMPs were active against fungi, but many of them were active at low concentrations (0.25–30 µM) against seven different bacteria. Hemolytic and cytotoxic activities were determined using pig erythrocytes and baby hamster kidney cells, respectively. The amino acid substitutions in the engineered AMPs did not inhibit cytotoxicity, but reduced hemolysis and therefore increased the therapeutic indices. The phylogenetic analysis of scorpion AMPs revealed they are closely related and the GXK motif is highly conserved. The engineered scorpion AMPs offer a promising alternative for the treatment of multidrug-resistant bacterial infections and could be modified further to reduce their hemolytic/cytotoxic activity.

Functional and immuno-reactive characterization of a previously undescribed peptide from the venom of the scorpion Centruroides limpidus

A previously undescribed toxic peptide named Cl13 was purified from the venom of the Mexican scorpion Centruroides limpidus. It contains 66 amino acid residues, including four disulfide bonds. The physiological effects assayed in 7 different subtypes of voltage gated Na⁺-channels, showed that it belongs to the β-scorpion toxin type. The most notorious effects were observed in subtypes Nav1.4, Nav1.5 and Nav1.6. Although having important sequence similarities with two other lethal toxins from this scorpion species (Cll1m and Cll2), the recently developed single chain antibody fragments (scFv) of human origin were not capable of protecting against Cl13. At the amino acid sequence level, in 3 stretches of peptide Cl13 (positions 7-9, 30-38 and 62-66) some differences with respect to other similar toxins are observed. Some of these differences coincide with contact points with the human antibody fragments.

Exon Shuffling and Origin of Scorpion Venom Biodiversity

Scorpion venom is a complex combinatorial library of peptides and proteins with multiple biological functions. A combination of transcriptomic and proteomic techniques has revealed its enormous molecular diversity, as identified by the presence of a large number of ion channel-targeted neurotoxins with different folds, membrane-active antimicrobial peptides, proteases, and protease inhibitors. Although the biodiversity of scorpion venom has long been known, how it arises remains unsolved. In this work, we analyzed the exon-intron structures of an array of scorpion venom protein-encoding genes and unexpectedly found that nearly all of these genes possess a phase-1 intron (one intron located between the first and second nucleotides of a codon) near the cleavage site of a signal sequence despite their mature peptides remarkably differ. This observation matches a theory of exon shuffling in the origin of new genes and suggests that recruitment of different folds into scorpion venom might be achieved via shuffling between body protein-coding genes and ancestral venom gland-specific genes that presumably contributed tissue-specific regulatory elements and secretory signal sequences.

rBmαTX14 Increases the Life Span and Promotes the Locomotion of Caenorhabditis Elegans

The scorpion has been extensively used in various pharmacological profiles or as food supplies. The exploration of scorpion venom has been reported due to the presence of recombinant peptides. rBmαTX14 is an α-neurotoxin extracted from the venom gland of the East Asian scorpion Buthus martensii Karsch and can affect ion channel conductance. Here, we investigated the functions of rBmαTX14 using the Caenorhabditis elegans model. Using western blot analysis, rBmαTX14 was shown to be expressed both in the cytoplasm and inclusion bodies in the E.coli Rosetta (DE3) strain. Circular dichroism spectroscopy analysis demonstrated that purified rBmαTX14 retained its biological structures. Next, feeding nematodes with E.coli Rosetta (DE3) expressing rBmαTX14 caused extension of the life span and promoted the locomotion of the nematodes. In addition, we identified several genes that play various roles in the life span and locomotion of C. elegans through microarray analysis and quantitative real-time PCR. Furthermore, if the amino acid site H₁₅ of rBmαTX14 was mutated, rBmαTX14 no longer promoted the C. elegans life span. In conclusion, the results not only demonstrated the functions and mechanism of rBmαTX14 in C. elegans, but also provided the new sight in the utility of recombinant peptides from scorpion venom.

Transgenic plants expressing the AaIT/GNA fusion protein show increased resistance and toxicity to both chewing and sucking pests

The adoption of pest-resistant transgenic plants to reduce yield losses and decrease pesticide use has been successful. To achieve the goal of controlling both chewing and sucking pests in a given transgenic plant, we generated transgenic tobacco, Arabidopsis, and rice plants expressing the fusion protein, AaIT/GNA, in which an insecticidal scorpion venom neurotoxin (Androctonus australis toxin, AaIT) is fused to snowdrop lectin (Galanthus nivalis agglutinin, GNA). Compared with transgenic tobacco and Arabidopsis plants expressing AaIT or GNA, transgenic plants expressing AaIT/GNA exhibited increased resistance and toxicity to one chewing pest, the cotton bollworm, Helicoverpa armigera. Transgenic tobacco and rice plants expressing AaIT/GNA showed increased resistance and toxicity to two sucking pests, the whitefly, Bemisia tabaci, and the rice brown planthopper, Nilaparvata lugens, respectively. Moreover, in the field, transgenic rice plants expressing AaIT/GNA exhibited a significant improvement in grain yield when infested with N. lugens. This study shows that expressing the AaIT/GNA fusion protein in transgenic plants can be a useful approach for controlling pests, particularly sucking pests which are not susceptible to the toxin in Bt crops.

A single-point mutation enhances dual functionality of a scorpion toxin

Scorpion venom represents a tremendous, hitherto partially explored peptide library that has been proven to be useful not only for understanding ion channels but also for drug design. MeuTXKα3 is a functionally unknown scorpion toxin-like peptide. Here we describe new transcripts of this gene arising from alternative polyadenylation and its biological function as well as a mutant with a single-point substitution at site 30. Native-like MeuTXKα3 and its mutant were produced in Escherichia coli and their toxic function against Drosophila Shaker K(+) channel and its mammalian counterparts (rKv1.1-rKv1.3) were assayed by two-electrode voltage clamp technique. The results show that MeuTXKα3 is a weak toxin with a wide-spectrum of activity on both Drosophila and mammalian K(+) channels. The substitution of a proline at site 30 by an asparagine, an evolutionarily conserved functional residue in the scorpion α-KTx family, led to an increased activity on rKv1.2 and rKv1.3 but a decreased activity on the Shaker channel without changing the potency on rKv1.1, suggesting a key role of this site in species selectivity of scorpion toxins. MeuTXKα3 was also active on a variety of bacteria with lethal concentrations ranging from 4.66 to 52.01μM and the mutant even had stronger activity on some of these bacterial species. To the best of our knowledge, this is the first report on a bi-functional short-chain peptide in the lesser Asian scorpion venom. Further extensive mutations of MeuTXKα3 at site 30 could help improve its K(+) channel-blocking and antibacterial functions.

Whole Transcriptome of the Venom Gland from Urodacus yaschenkoi Scorpion

Australian scorpion venoms have been poorly studied, probably because they do not pose an evident threat to humans. In addition, the continent has other medically important venomous animals capable of causing serious health problems. Urodacus yaschenkoi belongs to the most widely distributed family of Australian scorpions (Urodacidae) and it is found all over the continent, making it a useful model system for studying venom composition and evolution. This communication reports the whole set of mRNA transcripts produced by the venom gland. U. yaschenkoi venom is as complex as its overseas counterparts. These transcripts certainly code for several components similar to known scorpion venom components, such as: alpha-KTxs, beta-KTxs, calcins, protease inhibitors, antimicrobial peptides, sodium-channel toxins, toxin-like peptides, allergens, La1-like, hyaluronidases, ribosomal proteins, proteasome components and proteins related to cellular processes. A comparison with the venom gland transcriptome of Centruroides noxius (Buthidae) showed that these two scorpions have similar components related to biological processes, although important differences occur among the venom toxins. In contrast, a comparison with sequences reported for Urodacus manicatus revealed that these two Urodacidae species possess the same subfamily of scorpion toxins. A comparison with sequences of an U. yaschenkoi cDNA library previously reported by our group showed that both techniques are reliable for the description of the venom components, but the whole transcriptome generated with Next Generation Sequencing platform provides sequences of all transcripts expressed. Several of which were identified in the proteome, but many more transcripts were identified including uncommon transcripts. The information reported here constitutes a reference for non-Buthidae scorpion venoms, providing a comprehensive view of genes that are involved in venom production. Further, this work identifies new putative bioactive compounds that could be used to seed research into new pharmacological compounds and increase our understanding of the function of different ion channels.

Biochemical, transcriptomic and proteomic analyses of digestion in the scorpion Tityus serrulatus: insights into function and evolution of digestion in an ancient arthropod

Scorpions are among the oldest terrestrial arthropods and they have passed through small morphological changes during their evolutionary history on land. They are efficient predators capable of capturing and consuming large preys and due to envenomation these animals can become a human health challenge. Understanding the physiology of scorpions can not only lead to evolutionary insights but also is a crucial step in the development of control strategies. However, the digestive process in scorpions has been scarcely studied. In this work, we describe the combinatory use of next generation sequencing, proteomic analysis and biochemical assays in order to investigate the digestive process in the yellow scorpion Tityus serrulatus, mainly focusing in the initial protein digestion. The transcriptome generated database allowed the quantitative identification by mass spectrometry of different enzymes and proteins involved in digestion. All the results suggested that cysteine cathepsins play an important role in protein digestion. Two digestive cysteine cathepsins were isolated and characterized presenting acidic characteristics (pH optima and stability), zymogen conversion to the mature form after acidic activation and a cross-class inhibition by pepstatin. A more elucidative picture of the molecular mechanism of digestion in a scorpion was proposed based on our results from Tityus serrulatus. The midgut and midgut glands (MMG) are composed by secretory and digestive cells. In fasting animals, the secretory granules are ready for the next predation event, containing enzymes needed for alkaline extra-oral digestion which will compose the digestive fluid, such as trypsins, astacins and chitinase. The digestive vacuoles are filled with an acidic proteolytic cocktail to the intracellular digestion composed by cathepsins L, B, F, D and legumain. Other proteins as lipases, carbohydrases, ctenitoxins and a chitolectin with a perithrophin domain were also detected. Evolutionarily, a large gene duplication of cathepsin L occurred in Arachnida with the sequences from ticks being completely divergent from other arachnids probably due to the particular selective pressures over this group.

Transcriptome analysis of scorpion species belonging to the Vaejovis genus

Scorpions belonging to the Buthidae family have traditionally drawn much of the biochemist's attention due to the strong toxicity of their venoms. Scorpions not toxic to mammals, however, also have complex venoms. They have been shown to be an important source of bioactive peptides, some of them identified as potential drug candidates for the treatment of several emerging diseases and conditions. It is therefore important to characterize the large diversity of components found in the non-Buthidae venoms. As a contribution to this goal, this manuscript reports the construction and characterization of cDNA libraries from four scorpion species belonging to the Vaejovis genus of the Vaejovidae family: Vaejovis mexicanus, V. intrepidus, V. subcristatus and V. punctatus. Some sequences coding for channel-acting toxins were found, as expected, but the main transcribed genes in the glands actively producing venom were those coding for non disulfide-bridged peptides. The ESTs coding for putative channel-acting toxins, corresponded to sodium channel β toxins, to members of the potassium channel-acting α or κ families, and to calcium channel-acting toxins of the calcin family. Transcripts for scorpine-like peptides of two different lengths were found, with some of the species coding for the two kinds. One sequence coding for La1-like peptides, of yet unknown function, was found for each species. Finally, the most abundant transcripts corresponded to peptides belonging to the long chain multifunctional NDBP-2 family and to the short antimicrobials of the NDBP-4 family. This apparent venom composition is in correspondence with the data obtained to date for other non-Buthidae species. Our study constitutes the first approach to the characterization of the venom gland transcriptome for scorpion species belonging to the Vaejovidae family.

Scorpion peptide LqhIT2 activates phenylpropanoid pathways via jasmonate to increase rice resistance to rice leafrollers

LqhIT2 is an insect-specific toxin peptide identified in Leiurus quinquestriatus hebraeus that can be toxic to lepidoptera pests. However, whether LqhIT2 induces insect resistance in rice, and how the LqhIT2 influences the biochemical metabolism of rice plants remains unknown. Here, purified LqhIT2-GST fusion protein had toxicity to rice leafrollers. Meanwhile, in vitro and field trials showed that LqhIT2 transgenic rice plants were less damaged by rice leafrollers compared to the wild type plants. Introducing LqhIT2 primed the elevated expression of lipoxygenase, a key component of the jasmonic acid biosynthetic pathway, together with enhanced linolenic acid, cis-(+)-12-oxophytodienoic acid, jasmonic acid, and jasmonic acid-isoleucine levels. In addition, phenylalanine ammonia-lyase, a key gene of the phenylpropanoid pathway, was up-regulated. Correspondingly, the contents of downstream products of the phenylpropanoid pathway such as flavonoids and lignins, were also increased in LqhIT2 transgenic plants. These changes were paralleled by decreased starch, glucose, and glucose-6-phosphate accumulation, the key metabolites of glycolysis pathway that supplies the raw material and intermediate carbon products for phenylpropanoids biosyntheses. These findings suggest that, in addition to its own toxicity against pests, LqhIT2 activate the phenylpropanoid pathway via jasmonate-mediated priming, which subsequently increases flavonoid and lignin content and improves insect resistance in rice.

Bacterial overexpression of recombinant heteroscorpine-1 (rHS-1), a toxin from Heterometrus laoticus scorpion venom: trends for antibacterial application and antivenom production

Heteroscorpine-1 (HS-1) was identified as a member of the scorpine family. HS-1 shows insecticidal activities, exhibiting a low median lethal dose (LD50) in mealworm (Tenebrio molitor L.) and inhibitory activities against Bacillus subtilis, Klebsiella pneumoniae, and Pseudomonas aeruginosa. In this study, a recombinant HS-1 (rHS-1) was produced by overexpression in E. coli. A large yield of product was obtained. The structure of purified rHS-1 was confirmed through mass spectrometry. Both anti-crude venom and anti-rHS-1 antibodies specifically recognized rHS-1, suggesting its structural similarity. Reactivated rHS-1 caused roughening and blebbing of bacterial cell surfaces. It showed higher activity than that of pre-refolded protein. Antisera raised against a partially purified and mis- or unfolded peptide can inhibit relevant bioactivity.

Effects of dietary transgenic poplar leaf pellets on performance and tissues in rabbits

BACKGROUND

Various studies have been conducted to evaluate the effect of Bt crops on animals. Insect-resistant bioassays have revealed that the chitinase-BmkIT combination could be used as a new pest-resistant gene source and might be a complementary alien gene source to the Bt toxin gene. So it is necessary to assay the effects of chitinase-BmkIT plants on animals.

RESULTS

Forty 40-day old New Zealand White Rabbits (Oryctolagus cuniculus) were fed for 60 consecutive days with formulated feed containing dehydrated poplar (Populus cathayana Rehd) leaves harbouring chitinase-BmkIT gene combination or untransformed counterparts, and the potential toxicological effects of transgenic leaves on rabbits were explored. The results of the growth study revealed no significant differences for daily weight gain, feed intake and feed conversion ratio where they were 101.6%, 99.2% and 97.8% of the treatment compared to the control, respectively. No obvious pathological change was observed in the small intestine, stomach, spleen, kidney, lung, heart, bladder, pancreas, prostate and ovary. Electron microscopy observations of liver cells and renal cells showed they were both normal in the two groups. No feed-derived chitinase, BmkIT and NPTII genes were found in small intestine, blood, or leg muscle samples although they were detected in the formulated feed.

CONCLUSION

We conclude that the processed poplar leaves with foreign chitinase-BmkIT genes had no obviously harmful effects on rabbits.

Molecular, immunological, and biological characterization of Tityus serrulatus venom hyaluronidase: new insights into its role in envenomation

Background

Scorpionism is a public health problem in Brazil, and Tityus serrulatus (Ts) is primarily responsible for severe accidents. The main toxic components of Ts venom are low-molecular-weight neurotoxins; however, the venom also contains poorly characterized high-molecular-weight enzymes. Hyaluronidase is one such enzyme that has been poorly characterized.

Methods and principal findings

We examined clones from a cDNA library of the Ts venom gland and described two novel isoforms of hyaluronidase, TsHyal-1 and TsHyal-2. The isoforms are 83% identical, and alignment of their predicted amino acid sequences with other hyaluronidases showed conserved residues between evolutionarily distant organisms. We performed gel filtration followed by reversed-phase chromatography to purify native hyaluronidase from Ts venom. Purified native Ts hyaluronidase was used to produce anti-hyaluronidase serum in rabbits. As little as 0.94 µl of anti-hyaluronidase serum neutralized 1 LD₅₀ (13.2 µg) of Ts venom hyaluronidase activity in vitro. In vivo neutralization assays showed that 121.6 µl of anti-hyaluronidase serum inhibited mouse death 100%, whereas 60.8 µl and 15.2 µl of serum delayed mouse death. Inhibition of death was also achieved by using the hyaluronidase pharmacological inhibitor aristolochic acid. Addition of native Ts hyaluronidase (0.418 µg) to pre-neutralized Ts venom (13.2 µg venom+0.94 µl anti-hyaluronidase serum) reversed mouse survival. We used the SPOT method to map TsHyal-1 and TsHyal-2 epitopes. More peptides were recognized by anti-hyaluronidase serum in TsHyal-1 than in TsHyal-2. Epitopes common to both isoforms included active site residues.

Conclusions

Hyaluronidase inhibition and immunoneutralization reduced the toxic effects of Ts venom. Our results have implications in scorpionism therapy and challenge the notion that only neurotoxins are important to the envenoming process.

In Brazil, accidents with scorpion stings have been a serious public health problem, and Tityus serrulatus (Ts) is primarily responsible for severe accidents. Therefore, efforts have been made to understand the characteristics of the molecules present in scorpion venoms. These venoms are complex mixtures, in which neurotoxins are the main toxic components. Ts venom also contains enzymes, such as hyaluronidase, that have not been well characterized. In this study, we described for the first time two sequences of Ts hyaluronidase isoforms: TsHyal-1 and TsHyal-2. We purified native hyaluronidase from Ts venom and produced anti-hyaluronidase serum in rabbits. This serum neutralized hyaluronidase activity present in Ts venom. In vivo neutralization assays showed that anti-hyaluronidase serum inhibited and delayed mouse death after injection of a lethal dose (50% lethal dose, LD₅₀) of Ts venom. This work confirms the influence of hyaluronidase in Ts venom lethality and paves the way for the development of new strategies for scorpionism therapy.

Evolution stings: the origin and diversification of scorpion toxin peptide scaffolds

The episodic nature of natural selection and the accumulation of extreme sequence divergence in venom-encoding genes over long periods of evolutionary time can obscure the signature of positive Darwinian selection. Recognition of the true biocomplexity is further hampered by the limited taxon selection, with easy to obtain or medically important species typically being the subject of intense venom research, relative to the actual taxonomical diversity in nature. This holds true for scorpions, which are one of the most ancient terrestrial venomous animal lineages. The family Buthidae that includes all the medically significant species has been intensely investigated around the globe, while almost completely ignoring the remaining non-buthid families. Australian scorpion lineages, for instance, have been completely neglected, with only a single scorpion species (Urodacus yaschenkoi) having its venom transcriptome sequenced. Hence, the lack of venom composition and toxin sequence information from an entire continent’s worth of scorpions has impeded our understanding of the molecular evolution of scorpion venom. The molecular origin, phylogenetic relationships and evolutionary histories of most scorpion toxin scaffolds remain enigmatic. In this study, we have sequenced venom gland transcriptomes of a wide taxonomical diversity of scorpions from Australia, including buthid and non-buthid representatives. Using state-of-art molecular evolutionary analyses, we show that a majority of CSα/β toxin scaffolds have experienced episodic influence of positive selection, while most non-CSα/β linear toxins evolve under the extreme influence of negative selection. For the first time, we have unraveled the molecular origin of the major scorpion toxin scaffolds, such as scorpion venom single von Willebrand factor C-domain peptides (SV-SVC), inhibitor cystine knot (ICK), disulphide-directed beta-hairpin (DDH), bradykinin potentiating peptides (BPP), linear non-disulphide bridged peptides and antimicrobial peptides (AMP). We have thus demonstrated that even neglected lineages of scorpions are a rich pool of novel biochemical components, which have evolved over millions of years to target specific ion channels in prey animals, and as a result, possess tremendous implications in therapeutics.

Metabolic effect of an exogenous gene on transgenic Beauveria bassiana using liquid chromatography-mass spectrometry-based metabolomics

Genetic modification of Beauveria bassiana with the scorpion neurotoxin aaIT gene can distinctly increase its insecticidal activity, whereas the effect of this exogenous gene on the metabolism of B. bassiana is unknown until now. Thus, we investigate the global metabolic profiling of mycelia and conidia of transgenic and wild-type B. bassiana by liquid chromatography-mass spectrometry (LC-MS). Principal component analysis (PCA) and orthogonal projection to latent structure discriminant analysis (OPLS-DA) reveal clear discrimination of wild-type mycelia and conidia from transgenic mycelia and conidia. The decrease of glycerophospholipids, carnitine, and fatty acids and the increase of oxylipins, glyoxylate, pyruvic acid, acetylcarnitine, fumarate, ergothioneine, and trehalose in transgenic mycelia indicate the enhanced oxidative reactions. In contrast, most metabolites related to oxidative stress are not altered significantly in conidia, which implies that there will be no significant oxidative stress reaction when the aaIT gene is quiescent in cells.

Three new antimicrobial peptides from the scorpion Pandinus imperator

Three novel cysteine-free venom peptides, which were referred to as Pantinin-1, Pantinin-2 and Pantinin-3, respectively, have been identified from the scorpion Pandinus imperator by cDNA cloning strategy. The precursor of each peptide consists of a signal peptide, a mature peptide with no disulfide bridges, and an acidic propeptide with a typical processing signal. Each of the three peptides is an α-helical, cationic and amphipathic molecule with 13 or 14 amino acid residues. Their amino acid sequences are homologous to those of some 13-mer antimicrobial peptides isolated from scorpions. Antimicrobial assay showed that all the three peptides possess relatively strong activities against Gram-positive bacteria and a fungus, but have very weak antimicrobial activities against Gram-negative bacteria. Toxicity assay showed that the three peptides exhibit very low or mild hemolytic activities against human red blood cells. It is interesting to see that Pantinin-3 is able to potently inhibit the growth of vancomycin-resistant Enterococcus (VRE) S13, a pathogen that can cause a number of human infections; this suggests that Pantinin-3 has great potential to be applied in the treatment of VRE infections. Our findings gain new insights into the structure/function relationships of the small linear cationic antimicrobial peptides from scorpions, and provide new templates for designing of antimicrobial agents targeting antibiotic-resistant pathogenic bacteria.

Quantitative design of regulatory elements based on high-precision strength prediction using artificial neural network

Accurate and controllable regulatory elements such as promoters and ribosome binding sites (RBSs) are indispensable tools to quantitatively regulate gene expression for rational pathway engineering. Therefore, de novo designing regulatory elements is brought back to the forefront of synthetic biology research. Here we developed a quantitative design method for regulatory elements based on strength prediction using artificial neural network (ANN). One hundred mutated Trc promoter & RBS sequences, which were finely characterized with a strength distribution from 0 to 3.559 (relative to the strength of the original sequence which was defined as 1), were used for model training and test. A precise strength prediction model, NET90_19_576, was finally constructed with high regression correlation coefficients of 0.98 for both model training and test. Sixteen artificial elements were in silico designed using this model. All of them were proved to have good consistency between the measured strength and our desired strength. The functional reliability of the designed elements was validated in two different genetic contexts. The designed parts were successfully utilized to improve the expression of BmK1 peptide toxin and fine-tune deoxy-xylulose phosphate pathway in Escherichia coli. Our results demonstrate that the methodology based on ANN model can de novo and quantitatively design regulatory elements with desired strengths, which are of great importance for synthetic biology applications.

Insights into scorpion venom peptides: alternative processing of β-KTx propeptide from Tityus serrulatus venom results in a new naturally occurring thimet oligopeptidase inhibitor

Most functions attributed to Tityus serrulatus venom (TsV) are related to active molecules on ion-channels; however, here we describe a new pentapeptide that was discovered through enzymatic assay selection using EP24.15. The primary structure analysis revealed the sequence KEXXG (X means Ile or Leu), similar to the sequence present in the β-KTX propeptide described from the venom of Tityus spp. We confirmed through HPLC analysis that KEILG is the peptide present in TsV, but that KELLG also inhibits EP24.15 although through different mechanisms.

Scorpion toxins specific for potassium (K+) channels: a historical overview of peptide bioengineering

Scorpion toxins have been central to the investigation and understanding of the physiological role of potassium (K⁺) channels and their expansive function in membrane biophysics. As highly specific probes, toxins have revealed a great deal about channel structure and the correlation between mutations, altered regulation and a number of human pathologies. Radio- and fluorescently-labeled toxin isoforms have contributed to localization studies of channel subtypes in expressing cells, and have been further used in competitive displacement assays for the identification of additional novel ligands for use in research and medicine. Chimeric toxins have been designed from multiple peptide scaffolds to probe channel isoform specificity, while advanced epitope chimerization has aided in the development of novel molecular therapeutics. Peptide backbone cyclization has been utilized to enhance therapeutic efficiency by augmenting serum stability and toxin half-life in vivo as a number of K⁺-channel isoforms have been identified with essential roles in disease states ranging from HIV, T-cell mediated autoimmune disease and hypertension to various cardiac arrhythmias and Malaria. Bioengineered scorpion toxins have been monumental to the evolution of channel science, and are now serving as templates for the development of invaluable experimental molecular therapeutics.

[Codon optimization and eukaryotic expression analysis of the analgesic peptide gene BmK AngM1 from Buthus martensii Karsch]

Codon bias is an important factor which influences heterologous gene expression. Optimizing codon sequence could improve expression level of heterologous gene. In order to improve the expression level of BmK AngM1 gene encoding the analgesic peptide from Buthus martensii Karsch in Pichia pastoris, the codon-optimized BmK AngM1 gene according to its cDNA sequence and the preference codon usage of P. pastoris were cloned into expression vector pPIC9K and then transformed into P. pastoris. The expersion of recombinant BmK AngM1 (rBmK AngM1) was inducced by methanol in the medium, and the expression level of the optimized BmK AngM1 gene was 3.7 times of the native one. These results suggested that the expression of BmK AngM1 in P. pastoris could be successfully improved by codon optimization.

Purification and cDNA cloning of a novel neurotoxic peptide (Acra3) from the scorpion Androctonus crassicauda

Androctonus crassicauda is one of the Southeastern Anatolian scorpions of Turkey with ethno-medical and toxicological importance. Two toxic peptides (Acra1 and Acra2) were isolated and characterized from the venom of this scorpion. In this communication, the isolation of an additional toxin (Acra3) by chromatographic separations (HPLC and TSK-gel sulfopropyl) and its chemical and functional characterization is reported. Acra3 is a 7620Da molecular weight peptide, with 66 amino acid residues crosslinked by four disulfide bridges. The gene coding for this peptide was cloned and sequenced. Acra3 is anticipated to undergo post-translational modifications at the C-terminal region, having an amidated serine as last residue. Injection of Acra3 induces severe neurotoxic events in mice, such as: excitability and convulsions, leading to the death of the animals within a few minutes after injection. Electrophysiological assays conducted with pure Acra3, using cells that specifically expressed sodium channels (Nav1.1-Nav1.6) showed no clear effect. The exact molecular target of Acra3 remained undiscovered, similar to three other scorpion peptides that clustered very closely in the phylogenetic tree included here. The exact target of these four peptides is not very clear.

Tremendous intron length differences of the BmKBT and a novel BmKBT-like peptide genes provide a mechanical basis for the rapid or constitutive expression of the peptides

The cDNA sequence encoding a novel BmKBT-like peptide (referred to as BmKBy) was cloned and sequenced from the scorpion Mesobuthus martensii Karsch. Functional analysis indicated that both BmKBT and BmKBy possess strong toxicity in mice, but very weak toxicity in cotton bollworm. Phylogenetic analysis showed that BmKBy and BmKBT represent evolutionary intermediates between the α- and β-toxins from scorpions. The genomic sequences of BmKBT and BmKBy were also obtained. It is interesting to see that two genes, which contain an intron of 225 and 1529bp, respectively, exactly code for the BmKBT peptide. One gene, which contains an intron of 1312bp, codes for BmKBy. Given that genes with long introns favor constitutive expression, whereas those with short introns are rapidly regulated in response to stimulations, the BmKBT_a and BmKBT_b genes provide a mechanical basis for either constitutive expression or rapid generation of the toxic peptides in response to different signals.

BmK-YA, an enkephalin-like peptide in scorpion venom

By screening extracts of venom from the Asian scorpion Buthus martensii Karsch (BmK) for their abilities to activate opioid receptors, we have identified BmK-YA, an amidated peptide containing an enkephalin-like sequence. BmK-YA is encoded by a precursor that displays a signal sequence and contains four copies of BmK-YA sequences and four of His⁴-BmK-YA, all flanked by single amino acid residues. BmK-YA and His⁴-BmK-YA are amidated and thus fulfill the characteristics expected of bioactive peptides. BmK-YA can activate mammalian opioid receptors with selectivity for the δ subtype while His⁴-BmK-YA is inactive at opioid receptors. The discovery of BmK-YA suggests that scorpion venom may represent a novel source of bioactive molecules targeting G protein-coupled receptors (GPCRs) and reveal additional insights on the evolution of the opioid precursors.

Identification of a new specific Kv1.3 channel blocker, Ctri9577, from the scorpion Chaerilus tricostatus

Scorpion toxins are valuable resources for discovering new ion channel modulators and drug candidates. Potassium channel Kv1.3 is an important pharmacological target of T cell-mediated autoimmune diseases, which are encouraging the screening and design of the specific peptide blockers for Kv1.3 channel. Ctri9577, the first neurotoxin gene of Chaerilidae family was cloned from the venom of the scorpion Chaerilus tricostatus through the constructing its cDNA library. The sequence analysis showed that the mature peptide of Ctri9577 contained 39 amino acid residues including six conserved cysteines, whose low sequence similarity indicated that it was a new member of α-KTx15 subfamily. By using expression and purification technology, the recombinant peptide was obtained. Subsequently, the electrophysiological experiments indicated that the Ctri9577 peptide selectively inhibited Kv1.3 channel current with an IC(50) of 0.49±0.45 nM without effectively blocking potassium channels Kv1.1, Kv1.2, hERG and SK3. All these findings not only enrich the knowledge of toxins from the Chaerilidae family, but also present a novel potential drug candidate targeting Kv1.3 channels for the therapy of autoimmune diseases.

Identification and molecular characterization of three new K+-channel specific toxins from the Chinese scorpion Mesobuthus martensii Karsch revealing intronic number polymorphism and alternative splicing in duplicated genes

K(+)-channel specific toxins from scorpions are powerful probes used in the structural and functional characterization of different subfamilies of K(+)-channels which are thought to be the most diverse ion channels. However, only a limited number of K(+)-channel toxins have been identified from scorpions so far; moreover, little is known about the mechanisms for the generation of a combinatorial peptide library in a venom gland of a scorpion. Here, we identified and characterized three new K(+)-channel toxin-like peptides from the scorpion Mesobuthus martensii Karsch, which were referred to as BmKcug1, BmKcug2 and BmKcugx, respectively. BmKcug1 and BmKcug2 are two new members of α-KTx1 subfamily, and have been classified as α-KTx1.14 and α-KTx1.15, respectively. BmKcugx represents a new subfamily of K(+)-channel specific toxins which was classified into α-KTx22. BmKcugx was thus classified as α-KTx22.1. Genomic analysis demonstrated that BmKcugx gene has two exons interrupted by an intron inserted in the signal peptide encoding region, whereas BmKcug1a (a close homologue of BmKcug1)/BmKcug2 gene was interrupted by two introns, located within the 5'UTR of the gene and in the signal peptide encoding region, respectively. Transcriptomic analysis for the venom glands of M. martensii Karsch indicated that the abundances of the transcripts of BmKcug1a and BmKcug2 are much higher than that of BmKcugx; it suggests that the intron in 5'UTR could markedly increase the expression level of the K(+)-channel toxins. Alignment of the genomic sequences of BmKcug1a and BmKcug2 revealed that an alternative splicing event occurred at the intron 1-exon 2 junction in the 5'UTR of BmKcug2 transcript.

Gene cloning and functional characterization of four novel antimicrobial-like peptides from scorpions of the family Vaejovidae

From the cDNA libraries made from the venom glands of two scorpions belonging to the Vaejovidae family, four different putative non disulfide-bridged antimicrobial peptides were identified: VmCT1 and VmCT2 from Vaejovis mexicanus smithi plus VsCT1 and VsCT2 from Vaejovis subcristatus. These short peptides (with only 13 amino acid residues each) share important amino acid sequence similarities among themselves and with other reported antimicrobial peptides, but their biological activities vary dramatically. This communication reports the cloning, chemical synthesis and characterization of these peptides. Two peptides, VmCT1 and VmCT2 showed broad-spectrum antibacterial activity with minimum inhibitory concentrations MICs in the range of 5-25 μM and 10-20 μM respectively, whereas their hemolytic activity at these concentrations was low. Structure-function relationships that might determine the differences in activities are discussed.

Effects of BmKIT 3 R gene transfer on pupal development of Bombyx mori Linnaeus using a Gal4/UAS binary transgenic system

The pupal stage of the silkworm Bombyx mori Linnaeus lasts for approximately two weeks. However, prolongation of pupal duration would reduce the labor required to process and dry fresh cocoons. This study investigated the effects of BmKIT(3)(R) gene (from the Chinese scorpion Buthus martensii Karsch) transfer on the pupal development of B. mori using a Gal4/UAS binary transgenic system. Gal4 driven by a pupa-specific promoter BmWCP4 (from a B. mori wing-cuticle protein gene) or PDP (from a B. mori cocoonase gene), and BmKIT(3)(R) driven by a UAS cis-acting element were used to construct novel piggyBac-derived plasmids containing a neomycin-resistance gene (neo) controlled by the Bombyx mori nucleopolyhedrovirus (BmNPV) ie-1 (immediate-early gene) promoter and a green fluorescent protein gene (gfp) under the control of the B. mori actin 3 (A3) promoter. The vector was transferred into silkworm eggs by sperm-mediated gene transfer. Transgenic silkworms were produced after screening for neo and gfp genes, and gene transfer was verified by polymerase chain reaction and dot-blot hybridization. The larval development of the hybrid progeny of Gal4- and UAS-transgenic silkworms was similar to that of normal silkworms, but some pupae failed to metamorphose into moths, and the development of surviving pupae was arrested as a result of BmKIT(3)(R) expression. Moreover, Gal4 driven by the BmWCP4 promoter delayed pupal development more effectively than that driven by the PDP promoter in the Gal4/UAS binary transgenic system. Pupal durations of hybrid transgenic silkworm progeny with BmWCP4 and PDP promoters were approximately 5, 2, and 4 days longer, respectively, compared to corresponding normal silkworms, BmWCP4/Gal4, and UAS/BmKIT(3)(R) transgenic silkworms, respectively. These results suggest new avenues of research for prolonging the pupal duration of silkworms.

Characterization of BmKbpp, a multifunctional peptide from the Chinese scorpion Mesobuthus martensii Karsch: gaining insight into a new mechanism for the functional diversification of scorpion venom peptides

BmKbpp is a novel cationic and α-helical peptide from the Chinese scorpion Mesobuthus martensii Karsch, of which function or biological activity has not been characterized so far. Here we showed that BmKbpp possesses strong antimicrobial activity against both Gram-positive and Gram-negative bacteria with a MIC range from 2.3 μM to 68.2 μM for the majority of tested bacteria. BmKbpp also inhibits the growth of tested fungi with an IC50 range from 0.2 μM to 3.1 μM. Because BmKbpp potently inhibits the growth of some antibiotics-resistant pathogens, and shows very weak hemolytic activity, it has considerable potentials for therapeutic applications. Moreover, we found that BmKbpp markedly inhibits the superoxide production in granulocytes or HL-60 cells at the concentrations of submicromolar level; this suggests that BmKbpp can act as a signaling molecule involving innate immune regulation at low concentrations. The C-terminal region of BmKbpp (BmKbpp-C) shows 72% similarity to the peptide K-12, a bradykinin-potentiating peptide. We found that both BmKbpp and BmKbpp-C possess bradykinin-potentiating activity, and the activity of BmKbpp-C is stronger than that of BmKbpp. PCR amplification for the genomic gene of BmBpp showed that it is not a continuous sequence in the genome; it suggests that BmKbpp could come from a recombination event in transcript level. Taken together, our data suggest that multi-functionalization of a single peptide, which is probably mediated by trans-splicing, could be a new mechanism for the functional diversification of scorpion venom peptides.

[Construction and toxicity the recombinant SpltMNPV expressing the scorpion toxin gene]

OBJECTIVE

To develop a high toxic recombinant Spodoptera litura multicapsid nucleopolyhedroviruse (SpltMNPV) insecticide.

METHODS

We constructed a recombinant transfer vector that was characterized by disrupting of ecdysterioid UDP-glucosyltransferase (egt) gene and expressing the mature peptide of the Chinese scorpion, B. martensi Karsch (BmK ITal) gene at the control of ie-1 promoter. The transfer vector and the SpltMNPV II DNA cotransfected the SpLi cells. Recombinant viruses were purified by the end point dilution and fluorescent spot purification.

RESULTS

We successfully screened the recombinant SpltMNPV-deltaegt-Pph-egfp-ie-1-BmK ITal of which the egt gene was knocked out and expressed the mature peptide of the BmK ITal gene at the control of ie-1 promoter. Bioassays showed that, compared to the wide-type SpltMNPV, the speed of the recombinant virus killing the S. litura (LT50) increased by 0.7-0.8 days.

CONCLUSION

The insecticidal effect of SpltNPV could be increased by inserting the foreign gene, which provided a further opportunity to develop the SpltNPV into commercially viable products to control the S. litura.