Tc1, from Tityus cambridgei, is the first member of a new subfamily of scorpion toxin that blocks K+-channels

AbstractA new peptide, Tc1, containing only 23 amino acids closely packed by three disulfide bridges was isolated from the Amazonian scorpion Tityus cambridgei. It blocks reversibly the Shaker B K+-channels with a Kd of 65 nM and displaces binding of noxiustoxin to mouse brain synaptosome membranes. It is the shortest known peptide from scorpion venom that recognizes K+-channels and constitutes a new structural subfamily of toxin, classified as alphaKTx 13.1

Tetrapandins, a New Class of Scorpion Toxins That Specifically Inhibit Store-operated Calcium Entry in Human Embryonic Kidney-293 Cells

Venoms from 14 snakes and four scorpions were screened for inhibitory activities toward store-operated Ca2+ entry (SOCE) in human embryonic kidney-293 cells. An inhibitory activity was found in venom from the African scorpion Pandinus imperator. The active agent of this venom was purified by gel filtration and reverse-phase high pressure liquid chromatography methods. Sequence information on the purified fraction, by automatic Edman degradation and mass spectrometry analysis, identified the activity as being contained in two tetrapeptides, which we have named tetrapandins. We demonstrate that synthesized tetrapandins have inhibitory activity for SOCE in human embryonic kidney-293 cells while having no effect on either thapsigargin- or carbachol-stimulated release of Ca2+ stores. These toxins should be extremely useful in future studies to determine downstream events regulated by SOCE as well as to determine whether multiple pathways exist for thapsigargin-stimulated Ca2+ entry

Transcriptome analysis of the venom gland of the Mexican scorpion Hadrurus gertschi (Arachnida: Scorpiones)

<p>Abstract</p> <p>Background</p> <p>Scorpions like other venomous animals posses a highly specialized organ that produces, secretes and disposes the venom components. In these animals, the last postabdominal segment, named telson, contains a pair of venomous glands connected to the stinger. The isolation of numerous scorpion toxins, along with cDNA-based gene cloning and, more recently, proteomic analyses have provided us with a large collection of venom components sequences. However, all of them are secreted, or at least are predicted to be secretable gene products. Therefore very little is known about the cellular processes that normally take place inside the glands for production of the venom mixture. To gain insights into the scorpion venom gland biology, we have decided to perform a transcriptomic analysis by constructing a cDNA library and conducting a random sequencing screening of the transcripts.</p> <p>Results</p> <p>From the cDNA library prepared from a single venom gland of the scorpion <it>Hadrurus gertschi</it>, 160 expressed sequence tags (ESTs) were analyzed. These transcripts were further clustered into 68 unique sequences (20 contigs and 48 singlets), with an average length of 919 bp. Half of the ESTs can be confidentially assigned as homologues of annotated gene products. Annotation of these ESTs, with the aid of Gene Ontology terms and homology to eukaryotic orthologous groups, reveals some cellular processes important for venom gland function; including high protein synthesis, tuned posttranslational processing and trafficking. Nonetheless, the main group of the identified gene products includes ESTs similar to known scorpion toxins or other previously characterized scorpion venom components, which account for nearly 60% of the identified proteins.</p> <p>Conclusion</p> <p>To the best of our knowledge this report contains the first transcriptome analysis of genes transcribed by the venomous gland of a scorpion. The data were obtained for the species <it>Hadrurus gertschi</it>, belonging to the family Caraboctonidae. One hundred and sixty ESTs were analyzed, showing enrichment in genes that encode for products similar to known venom components, but also provides the first sketch of cellular components, molecular functions, biological processes and some unique sequences of the scorpion venom gland.</p

Pi5 and Pi6, two undescribed peptides from the venom of the scorpion Pandinus imperator and their effects on K + -channels

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Isolation, chemical and functional characterization of several new K+-channel blocking peptides from the venom of the scorpion Centruroides tecomanus

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Inhibition of the Collapse of the Shaker K+ Conductance by Specific Scorpion Toxins

The Shaker B K+ conductance (GK) collapses when the channels are closed (deactivated) in Na+ solutions that lack K+ ions. Also, it is known that external TEA (TEAo) impedes the collapse of GK (Gómez-Lagunas, F. 1997. J. Physiol. 499:3–15; Gómez-Lagunas, F. 2001. J. Gen. Physiol. 118:639–648), and that channel block by TEAo and scorpion toxins are two mutually exclusive events (Goldstein, S.A.N., and C. Miller. 1993. Biophys. J. 65:1613–1619). Therefore, we tested the ability of scorpion toxins to inhibit the collapse of GK in 0 K+. We have found that these toxins are not uniform regarding the capacity to protect GK. Those toxins, whose binding to the channels is destabilized by external K+, are also effective inhibitors of the collapse of GK. In addition to K+, other externally added cations also destabilize toxin block, with an effectiveness that does not match the selectivity sequence of K+ channels. The inhibition of the drop of GK follows a saturation relationship with [toxin], which is fitted well by the Michaelis-Menten equation, with an apparent Kd bigger than that of block of the K+ current. However, another plausible model is also presented and compared with the Michaelis-Menten model. The observations suggest that those toxins that protect GK in 0 K+ do so by interacting either with the most external K+ binding site of the selectivity filter (suggesting that the K+ occupancy of only that site of the pore may be enough to preserve GK) or with sites capable of binding K+ located in the outer vestibule of the pore, above the selectivity filter

Resurgent Current and Voltage Sensor Trapping Enhanced Activation by a β-Scorpion Toxin Solely in Nav1.6 Channel SIGNIFICANCE IN MICE PURKINJE NEURONS

Abstract Resurgent currents are functionally crucial in sustaining the high frequency firing of cerebellar Purkinje neurons expressing Nav1.6 channels. β-Scorpion toxins, such as CssIV, induce a left shift in the voltage-dependent activation of Nav1.2 channels by "trapping" the IIS4 voltage sensor segment. We found that the dangerous Cn2 β-scorpion peptide induces both the left shift voltage-dependent activation and a transient resurgent current only in human Nav1.6 channels (among 1.1-1.7), whereas CssIV did not induce the resurgent current. Cn2 also produced both actions in mouse Purkinje cells. These findings suggest that only distinct β-toxins produce resurgent currents. We suggest that the novel and unique selectivity of Cn2 could make it a model drug to replace deep brain stimulation of the subthalamic nucleus in patients with Parkinson disease