Topic
Parabuthus transvaalicus
About: Parabuthus transvaalicus is a research topic. Over the lifetime, 27 publications have been published within this topic receiving 741 citations. The topic is also known as: Transvaal Thicktail scorpion.
Papers
TL;DR: It is proposed that the prevenom of scorpions is used as a highly efficacious predator deterrent and for immobilizing small prey while conserving metabolically expensive venom until a certain level of stimuli is reached, after which the venom is secreted.
Abstract: Scorpion venom is a complex mixture of salts, small molecules, peptides, and proteins. Scorpions employ this valuable tool in several sophisticated ways for subduing prey, deterring predators, and possibly during mating. Here, a subtle but clever strategy of venom utilization by scorpions is reported. Scorpions secrete a small quantity of transparent venom when initially stimulated that we propose to name prevenom. If secretion continues, a cloudy and dense venom that is white in color is subsequently released. The prevenom contains a combination of high K+ salt and several peptides including some that block rectifying K+ channels and elicit significant pain and toxicity because of a massive local depolarization. The presence of high extracellular K+ in the prevenom can depolarize cells and also decrease the local electrochemical gradient making it more difficult to reestablish the resting potential. When this positive change to the K+ equilibrium potential is combined with the blockage of rectifying K+ channels, this further delays the recovery of the resting potential, causing a prolonged effect. We propose that the prevenom of scorpions is used as a highly efficacious predator deterrent and for immobilizing small prey while conserving metabolically expensive venom until a certain level of stimuli is reached, after which the venom is secreted.
171 citations
TL;DR: These scorpions perceive risk and regulate venom expenditure during stinging according to level of threat, providing further support for the venom-metering hypothesis.
60 citations
TL;DR: The discovery of birtoxin, a bioactive long chain neurotoxin peptide with only three disulfide bridges, offers new insight into understanding the role of conserved disulfides bridges with respect to scorpion toxin structure and function.
Abstract: The venom of the South African scorpion Parabuthus transvaalicus was characterized using a combination of mass spectrometry and RP-HPLC separation and bioassays. The crude venom was initially separated into 10 fractions. A novel, moderately toxic but very high abundance peptide (birtoxin) of 58 amino-acid residues was isolated, identified and characterized. Each purification step was followed by bioassays and mass spectroscopy. First a C4 RP-HPLC column was used, then a C18 RP Microbore column purification resulted in . 95% purity in the case of birtoxin from a starting material of 230 mg of crude venom. About 12‐14% of the D214 absorbance of the total venom as observed after the first chromatography step was composed of birtoxin. This peptide was lethal to mice at low microgram quantities and it induced serious symptoms including tremors, which lasted up to 24 h post injection, at submicrogram amounts. At least seven other fractions that showed different activities including one fraction with specificity against blowfly larvae were identified. Identification of potent components is an important step in designing and obtaining effective antivenom. Antibodies raised against the critical toxic components have the potential to block the toxic effects and reduce the pain associated with the scorpion envenomation. The discovery of birtoxin, a bioactive long chain neurotoxin peptide with only three disulfide bridges, offers new insight into understanding the role of conserved disulfide bridges with respect to scorpion toxin structure and function.
58 citations
TL;DR: Tests confirm that toxins which inhibit potassium channels and alter sodium channel gating are present in the venoms studied, and point to a clear interspecies relationship within the genus Parabuthus.
32 citations
TL;DR: Phaiodotoxin is the first toxic peptide ever purified from a scorpion of the family Iuridae, and shifts the voltage dependence of activation and inactivation of insect Na+ channels (para/tipE) to more negative and positive potentials, respectively.
Abstract: A peptide called phaiodotoxin was isolated from the venom of the scorpion Anuroctonus phaiodactylus. It is lethal to crickets, but non toxic to mice at the doses assayed. It has 72 amino acid residues, with a molecular mass of 7971 atomic mass units. Its covalent structure was determined by Edman degradation and mass spectrometry; it contains four disulfide-bridges, of which one of the pairs is formed between cysteine-7 and cysteine-8 (positions Cys63-Cys71). The other three pairs are formed between Cys13-Cys38, Cys23-Cys50 and Cys27-Cys52. Comparative sequence analysis shows that phaiodotoxin belongs to the long-chain subfamily of scorpion peptides. Several genes coding for this peptide and similar ones were cloned by PCR, using cDNA prepared from the RNA of venomous glands of this scorpion. Electrophysiological assays conducted with this toxin in several mammalian cell lines (TE671, COS7, rat GH3 and cerebellum granular cells), showed no effect on Na+ currents. However, it shifts the voltage dependence of activation and inactivation of insect Na+ channels (para/tipE) to more negative and positive potentials, respectively. Therefore, the 'window' current is increased by 225%, which is thought to be the cause of its toxicity toward insects. Phaiodotoxin is the first toxic peptide ever purified from a scorpion of the family Iuridae.
29 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2019 | 1 |
| 2015 | 3 |
| 2012 | 2 |
| 2011 | 1 |
| 2010 | 1 |
| 2008 | 1 |