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Channel Toxin (channel + toxin)
Selected AbstractsMolecular cloning, genomic organization and functional characterization of a new short-chain potassium channel toxin-like peptide BmTxKS4 from Buthus martensii Karsch(BmK)JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 4 2004Sheng Jiqun Abstract Scorpion venom contains many small polypeptide toxins, which can modulate Na+, K+, Cl,, and Ca2+ ion,channel conductance in the cell membrane. A full-length cDNA sequence encoding a novel type of K+ -channel toxin (named BmTxKS4) was first isolated and identified from a venom gland cDNA library of Buthus martensii Karsch (BmK). The encoded precursor contains 78 amino acid residues including a putative signal peptide of 21 residues, propeptide of 11 residues, and a mature peptide of 43 residues with three disulfide bridges. BmTxKS4 shares the identical organization of disulfide bridges with all the other short-chain K+ -channel scorpion toxins. By PCR amplification of the genomic region encoding BmTxKS4, it was shown that BmTxKS4 composed of two exons is disrupted by an intron of 87 bp inserted between the first and the second codes of Phe (F) in the encoding signal peptide region, which is completely identical with that of the characterized scorpion K+ -channel ligands in the size, position, consensus junctions, putative branch point, and A+T content. The GST-BmTxKS4 fusion protein was successfully expressed in BL21 (DE3) and purified with affinity chromatography. About 2.5 mg purified recombinant BmTxKS4 (rBmTxKS4) protein was obtained by treating GST-BmTxKS4 with enterokinase and sephadex chromatography from 1 L bacterial culture. The electrophysiological activity of 1.0,M rBmTxKS4 was measured and compared by whole cell patch-clamp technique. The results indicated that rBmTxKS4 reversibly inhibited the transient outward K+ current (Ito), delayed inward rectifier K+ current (Ik1), and prolonged the action potential duration of ventricular myocyte, but it has no effect on the action potential amplitude. Taken together, BmTxKS4 is a novel subfamily member of short-strain K+ -channel scorpion toxin. © 2004 Wiley Periodicals, Inc. J Biochem Mol Toxicol 18:187,195, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20026 [source] Chlorotoxin does not inhibit volume-regulated, calcium-activated and cyclic AMP-activated chloride channelsBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2000Chantal Maertens It was the aim of this study to look for a high-affinity and selective polypeptide toxin, which could serve as a probe for the volume-regulated anion channel (VRAC) or the calcium-activated chloride channel (CaCC). We have partially purified chlorotoxin, including new and homologous short chain insectotoxins, from the crude venom of Leiurus quinquestriatus quinquestriatus (Lqq) by means of gel filtration chromatography. Material eluting between 280 and 420 min, corresponding to fractions 15,21, was lyophilized and tested on VRAC and CaCC, using the whole-cell patch-clamp technique. We have also tested the commercially available chlorotoxin on VRAC, CaCC, the cystic fibrosis transmembrane conductance regulator (CFTR) and on the glioma specific chloride channel (GCC). VRAC and the correspondent current, ICl,swell, was activated in Cultured Pulmonary Artery Endothelial (CPAE) cells by a 25% hypotonic solution. Neither of the fractions 16,21 significantly inhibited ICl,swell (n=4,5). Ca2+ -activated Cl, currents, ICl,Ca, activated by loading T84 cells via the patch pipette with 1 ,M free Ca2+, were not inhibited by any of the tested fractions (15,21), (n=2,5). Chlorotoxin (625 nM) did neither effect ICl,swell nor ICl,Ca (n=4,5). The CFTR channel, transiently transfected in COS cells and activated by a cocktail containing IBMX and forskolin, was not affected by 1.2 ,M chlorotoxin (n=5). In addition, it did not affect currents through GCC. We conclude that submicromolar concentrations of chlorotoxin do not block volume-regulated, Ca2+ -activated and CFTR chloride channels and that it can not be classified as a general chloride channel toxin. British Journal of Pharmacology (2000) 129, 791,801; doi:10.1038/sj.bjp.0703102 [source] Molecular diversity of toxic components from the scorpion Heterometrus petersii venom revealed by proteomic and transcriptome analysisPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 13 2010Yibao Ma Abstract Scorpion venoms contain a vast untapped reservoir of natural products, which have the potential for medicinal value in drug discovery. In this study, toxin components from the scorpion Heterometrus petersii venom were evaluated by transcriptome and proteome analysis. Ten known families of venom peptides and proteins were identified, which include: two families of potassium channel toxins, four families of antimicrobial and cytolytic peptides, and one family from each of the calcium channel toxins, La1-like peptides, phospholipase A2, and the serine proteases. In addition, we also identified 12 atypical families, which include the acid phosphatases, diuretic peptides, and ten orphan families. From the data presented here, the extreme diversity and convergence of toxic components in scorpion venom was uncovered. Our work demonstrates the power of combining transcriptomic and proteomic approaches in the study of animal venoms. [source] Characterization of two Bunodosoma granulifera toxins active on cardiac sodium channelsBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2001Cyril Goudet Two sodium channel toxins, BgII and BgIII, have been isolated and purified from the sea anemone Bunodosoma granulifera. Combining different techniques, we have investigated the electrophysiological properties of these toxins. We examined the effect of BgII and BgIII on rat ventricular strips. These toxins prolong action potentials with EC50 values of 60 and 660 nM and modify the resting potentials. The effect on Na+ currents in rat cardiomyocytes was studied using the patch-clamp technique. BgII and BgIII slow the rapid inactivation process and increase the current density with EC50 values of 58 and 78 nM, respectively. On the cloned hH1 cardiac Na+ channel expressed in Xenopus laevis oocytes, BgII and BgIII slow the inactivation process of Na+ currents (respective EC50 values of 0.38 and 7.8 ,M), shift the steady-state activation and inactivation parameters to more positive potentials and the reversal potential to more negative potentials. The amino acid sequences of these toxins are almost identical except for an asparagine at position 16 in BgII which is replaced by an aspartic acid in BgIII. In all experiments, BgII was more potent than BgIII suggesting that this conservative residue is important for the toxicity of sea anemone toxins. We conclude that BgII and BgIII, generally known as neurotoxins, are also cardiotoxic and combine the classical effects of sea anemone Na+ channels toxins (slowing of inactivation kinetics, shift of steady-state activation and inactivation parameters) with a striking decrease on the ionic selectivity of Na+ channels. British Journal of Pharmacology (2001) 134, 1195,1206; doi:10.1038/sj.bjp.0704361 [source] | ||||||||||