Synthesis and expression of the gene coding for noxiustoxin, a K+ channel-blocking peptide from the venom of the scorpion Centruroides noxius

Microbial production of toxins from the scorpion venom: properties and applications

Scorpion venom are composed mainly of bioactive proteins and peptides that may serve as lead compounds for the design of biotechnological tools and therapeutic drugs. However, exploring the therapeutic potential of scorpion venom components is mainly impaired by the low yield of purified toxins from milked venom. Therefore, production of toxin-derived peptides and proteins by heterologous expression is the strategy of choice for research groups and pharmaceutical industry to overcome this limitation. Recombinant expression in microorganisms is often the first choice, since bacteria and yeast systems combine high level of recombinant protein expression, fast cell growth and multiplication and simple media requirement. Herein, we present a comprehensive revision, which describes the scorpion venom components that were produced in their recombinant forms using microbial systems. In addition, we highlight the pros and cons of performing the heterologous expression of these compounds, regarding the particularities of each microorganism and how these processes can affect the application of these venom components. The most used microbial system in the heterologous expression of scorpion venom components is Escherichia coli (85%), and among all the recombinant venom components produced, 69% were neurotoxins. This review may light up future researchers in the choice of the best expression system to produce scorpion venom components of interest.

Gene construction, expression and functional testing of an inotropic peptide from the venom of the black scorpion Hottentotta judaicus

Anti-insect depressant toxins represent a subfamily of scorpion venom-derived β-toxins that are polypeptides composed of 61-65 amino acid residues stabilized by four disulfide bridges. These toxins affect the activation of voltage-sensitive sodium channels (NaScTx) and exhibit the preferential ability to induce flaccid paralysis in insect larvae. Here we demonstrate the recombinant expression of the novel cardiac inotropic peptide (Bj-IP) that was classified as an anti-insect depressant βNaScTx isolated from the venom of Hottentotta judaicus. By using "splicing by overlap extension" (SOE)-PCR, allowing for the first time one step de novo synthesis of long-chain scorpion toxin genes, we generated a codon-optimized DNA fragment of Bj-IP for cloning into the Escherichia coli vector pQE30. Moreover, the gene of interest was fused to a 6xHis coding DNA sequence. Subsequent recombinant expression was performed in E. coli KRX. The purification of the polypeptide was achieved by a combination of NiNTA agarose columns and RP (C(18)) high-performance liquid chromatography. The purified fusion protein was digested with factor Xa resulting in the elution of Bj-IP. The yield of recombinant Bj-IP expression was approximately 4.5 mg per liter of culture. Mass spectrometry confirmed the theoretical total mass of Bj-IP (6608 Da). Tag-free Bj-IP was refolded in guanidine chloride buffer with a glutathione redox system which was supplemented with different additives at 16 °C. Supplementation with 10% glycerol produced Bj-IP folding forms that exhibited reproducible biological activity in mouse cardiomyocytes. Cell contractility was increased by almost 3-fold and decay kinetics were hasten by 47% after administration of Bj-IP. Taken together, here we show the recombinant expression of the functionally active cardiac inotropic peptide Bj-IP, a new βNaScTx from H. judaicus, for promising pharmacological applications. Furthermore, our data suggest that the use of SOE-PCR may help to facilitate in future the high throughput of cloning and/or modification of scorpion toxin genes.

Scorpion and spider venom peptides: gene cloning and peptide expression

This communication reviews most of the important findings related to venom components isolated from scorpions and spiders, mainly by means of gene cloning and expression. Rather than revising results obtained by classical biochemical studies that report structure and function of venom components, here the emphasis is placed on cloning and identification of genes present in the venomous glands of these arachnids. Aspects related to cDNA library construction, specific or random ESTs cloning, transcriptome analysis, high-throughput screening, heterologous expression and folding are briefly discussed, showing some numbers of species and components already identified, but also shortly mentioning limitations and perspectives of research for the future in this field.

Molecular cloning and sequencing of two 'short chain' and two 'long chain' K(+) channel-blocking peptides from the Chinese scorpion Buthus martensii Karsch

Five full-length cDNAs encoding the precursors of two 'short chain' scorpion non-toxic peptides active on Ca(2+)-activated K(+) channels (BmP02 and BmP03) and two novel putative long chain K(+) channel-blocking peptides (named BmTXKbeta and BmTXKbeta2) were first isolated from the venom gland cDNA library of the Chinese scorpion Buthus martensii Karsch (BmK). BmTXKbeta2 showed a high similarity with AaTXKbeta, while BmTXKbeta was completely different in the deduced primary structure from the long chain and short chain scorpion toxins already characterized. Thus, BmTXKbeta expands the scorpion long chain K(+) channel-blocking peptide family. Although little sequence similarity exists between the above two short and two long peptides, they are similar at the positions of six cysteines, suggesting that they should all share a similar scaffold composed of an alpha-helix and a three-stranded beta-sheet.

From noxiustoxin to Shiva-3, a peptide toxic to the sporogonic development of Plasmodium berghei

This communication reviews shortly the main structural and functional characteristics of Noxiustoxin, a 39 amino acid residue peptide, maintained closely packed by three-disulfide bridges and its effects on excitable membranes. Shiva-3, a cecropin like-peptide composed of 38 amino acid residues is also briefly reviewed. Its design and synthesis was made possible by the expertise gained through the work previously performed with Noxiustoxin. One of the most prominent functional characteristics of Shiva-3 is the toxic effect upon the sporogonic development of Plasmodium berghei (responsible for a murine version of malaria). A synthetic Shiva-3 gene was constructed by recursive polymerase-chain reaction (PCR) methodology and expressed using the vector pGEX2T as a hybrid protein between the glutathione-S-transferase at the N-terminal and Shiva-3 in the C-terminal part of the hybrid. The recombinant protein kills bacteria and Plasmodium berghei. The future aim of this work is to produce a transgenic mosquito that carries the message for synthesis and excretion of Shiva-3 and similar peptides, in the midgut of mosquitoes, in an attempt to control the spreading of human malaria.

Site directed mutants of Noxiustoxin reveal specific interactions with potassium channels

Several site directed mutations were introduced into a synthetic Noxiustoxin (NTX) gene. Alanine scanning of the nonapeptide at the N-terminal segment of NTX (threonine 1 (T1) to serine 9 (S9)) was constructed and the recombinant products were obtained in pure form. Additionally, lysine 28 (K28) was changed to arginine (R) or glutamic acid (E), cysteine 29 was changed to alanine, and residues 37-39 (Tyr-Asn-Asn) of the carboxyl end were deleted. The recombinant mutants were tested for their ability to displace 125I-NTX from rat brain synaptosome membranes, as well as for their efficiency in blocking the activity of Kv1.1 K+ channels expressed in Xenopus laevis oocytes. The main results indicate that residues K6, T8 at the amino end, and K28 and the tripeptide YNN at the carboxyl end are involved in specific interactions of NTX with rat brain and/or Kv1.1 K+ channels.