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At least 1,063 records · Page 59Linked to original sources
PubMed1988

Solution spatial structure of 'long' neurotoxin M9 from the scorpion Buthus eupeus by 1H-NMR spectroscopy.

1H-NMR spectra of Buthus eupeus neurotoxin M9 (66 amino acid residues, four disulfide bonds) reveal two slowly exchangeable conformations at acidic pH. The spatial structure of the conformer prevailing under physiologically relevant conditions has been determined from two-dimensional 1H-NMR data treated by means of a distance geometry algorithm and refined by molecular modelling. Interrelation between the structure and function of mammalian neurotoxin M9 is discussed by comparing its conformation with those of the scorpion insectotoxins which exhibit different biological specificity (insectotoxins v-2, v-3 and I5A).

Amino Acid Sequence↗
PubMed1990

Nested allostery in scorpion hemocyanin (Pandinus imperator).

The oxygen-binding behavior of the 24-meric hemocyanin of the scorpion Pandinus imperator and its dependence on allosteric effectors such as protons can be successfully described by the nesting model; the MWC model is not acceptable. The affinities of the four assumed conformations of the allosteric unit, the 12-meric half-molecule, are not dependent on pH whereas the three allosteric equilibrium constants decrease with decreasing proton concentration. Comparison with the oxygen-binding behavior of the 24-meric tarantula hemocyanin (Eurypelma californicum) reveals that the affinity values for the various conformations seem to be conserved for chelicerata hemocyanin.

Allosteric Site↗
PubMed1982

Electron microscopic evidence for scorpion toxin binding to synapses of rat brain cortex.

The venom from the scorpion Centruroides noxius Hoffman was fractionated by Sephadex G-50 gel filtration. The toxic fraction (n.II) was coupled to Sepharose-4B and used for purification of specific horse immunoglobulins. The purified immunoglobulins were linked to ferritin with glutaraldehyde and repurified in the same affinity column. This complex bound to the postsynaptic membrane of rat brain tissue previously exposed to toxin.

Animals↗
PubMed1983

Voltage-sensitive Na+ channels in the neurohypophysis of the rat as demonstrated by 125I-labelled scorpion toxin.

Fresh rat neural lobe slices were incubated in the presence of [125I] alpha-scorpion toxin (ScTX), a specific marker of Na+ channels. Quantitative electron microscope autoradiography revealed preferential, irregularly spaced labeling of the axolemma of neurosecretory axons, with a significantly higher crude specific activity than any other neuronal or non-neuronal compartment. The number of specific binding sites at the neural lobe surface was calculated to be about 23 per microns2 of axolemma.

Animals↗
PubMed1994

Isolation and characterization of TsTX-V, a new neurotoxin from Tityus serrulatus scorpion venom which delays the inactivation of Na+ channels.

TsTX-V, a new neurotoxin from Tityus serrulatus scorpion venom able to induce a prolongation of the inactivation of Na+ channels, has been purified to homogeneity. The venom was chromatographed on CM-cellulose-52 and 13 fractions were first collected. A subsequent stepwise elution chromatography of fraction XI afforded, among other toxins, highly purified TsTX-V, which showed a single band by PAGE, SDS-PAGE or isoelectric focusing, a distinctive amino acid composition, mol. wt. = 7230, pI = 8.0 and i.v. LD50 = 94 +/- 7 micrograms/kg in mice. TsTX-V induced a long lasting hypertension in anesthetized rats and prolonged the action potential of the B fibers of the rabbit vagus nerve at 0.03 microgram/ml. At 0.3 microgram/ml and higher concentrations it caused also a nerve depolarization. These effects on nerve membranes were irreversible and could be suppressed by tetrodotoxin (200-500 nM). Nerve fibers depolarized by high extracellular K+(15-30mM) concentrations still displayed long duration action potentials after TsTX-V treatment. It is suggested that TsTX-V blocks the Na+ channel inactivation system probably as an alpha-toxin.

Action Potentials↗
PubMed1976

Supersensitivity induced by the toxin of Brazilian scorpion venom (Tityus serrulatus Lutz e Mello).

The purified toxin of the Brazilian scorpion venom (TsTX) enhances the pharmacological actions of directly and indirectly acting substances on several preparations. The enhancing action of TsTX is more pronounced for the indirectly acting drugs, which is highly suggestive of a prejunctional site of action. Secondarily, TsTX does also produce an unspecific increase of sensitivity at the level of the pharmacological receptor itself. The mechanism by which these changes are brought about remains to be determined.

Acetylcholine↗
PubMed1976

Potentiation of bradykinin action on smooth muscle by a scorpion venom extract.

Gel filtration of the water extract of the venom of the scorpion T. serrulatus showed four peaks; the first peak (P1) is devoid of toxic activity but increases the bradykinin-induced contraction of isolated rat uterus and guinea-pig ileum. The stepwise fractionation of the pooled P1 peak was performed in a DEAE-cellulose column and the bradykinin potentiating activity was found in the second protein peak. Finger-printing of this material showed that the bradykinin potentiating material migrates to the anode, giving two spots when submitted to chromatography, the activity being found in the spot that presents the greatest Rf. The potentiator is destroyed by heating at 97 degrees C, is not dialysable and is destroyed by incubation with pronase. Some of these properties differentiate it from the BPF's from snake venoms.

Animals↗
PubMed1980

Ultrastructure of the flagellum in sperms of the scorpion Tityus bahiensis.

In spermatids of the scorpion Tityus bahiensis two centrioles appear coaxially aligned. The flagellum shows 9 peripheral doublets and a central rod (9 + 1 pattern). This central rod, of about 15 nm in diameter, is positively stained when a cytochemical method for histone staining is used. Longitudinal sections show that radial spokes are apparently in groups of three and showing a basic repeat of about 94 nm.

Animals↗
PubMed1993

Cloning and characterization of cDNAs that code for Na(+)-channel-blocking toxins of the scorpion Centruroides noxius Hoffmann.

With the purpose of studying the organization and characteristics of the genes that code for toxins present in the venom of the Mexican scorpion, Centruroides noxius Hoffmann (CnH), we prepared a lambda gt11 cDNA library from the venom glands. Using specific oligodeoxyribonucleotides (oligos) designed according to known amino acid (aa) sequences of CnH toxins (STox), we detected several positive clones, determined their nucleotide (nt) sequences and deduced their aa sequences. A comparative analysis of these sequences with previously reported STox revealed that CnH cDNAs code for a family of very similar STox. The cDNA coding for a known STox, II-10, was cloned. Additionally, three other complete (new) nt sequences were obtained for cDNAs encoding peptides similar to STox 1 from CnH or variants 2 and 3 from Centruroides sculpturatus Ewing. Southern blot genomic DNA analysis showed a minimum size of approximately 600 bp as EcoRI fragments for elements of this family. PCR amplifications of CnH genomic DNA and hybridization of PCR products with specific probes indicated that the genomic structural regions that code for these genes do not contain introns, or at least not large introns.

Amino Acid Sequence↗
PubMed1992

Effect of scorpion Leiurus quinquestriatus (H&E) venom on the clinical chemistry parameters of the rat.

Egyptian scorpion venom was collected by electrical stimulation of the telson. Rats were injected with the lyophilized venom in 3 different doses (100, 200 and 400 micrograms/kg). Blood samples were drawn by heart puncture before and 4 h after venom administration. Serum was separated and collected for determination of glucose, blood urea nitrogen (BUN), creatinine, uric acid (UA), total proteins, cholesterol, sodium, potassium, calcium, inorganic phosphorus, alkaline phosphatase, aspartate aminotransferase (AST, GOT), alanine aminotransferase (ALT, GPT), lactate dehydrogenase and creatine phosphokinase (CPK). Serum glucose, creatinine, GOT, GPT and LDH were increased significantly in all treatments. At the same time serum BUN and CPK were elevated significantly with a dose-response relationship. On the other hand, serum total proteins, uric acid, cholesterol, calcium and potassium were significantly decreased 4 h after administration of the 3 doses. These changes in clinical chemistry parameters are most probably related to the toxic effect of the venom on the target organs.

Animals↗
PubMed1992

Effect of scorpion Leiurus quinquestriatus (H&E) venom on rat's heart rate and blood pressure.

The effects of scorpion Leiurus quinquestriatus (H&E) venom collected from the South Sinai region, Egypt, on heart rate (HR) and mean arterial pressure (MAP) were studied after intramuscular administration of 3 different doses (100, 200 and 400 micrograms/kg) to anesthetized rats. The effects of adrenergic and cholinergic blocking agents on the venom-induced HR and MAP changes were also evaluated. In two groups of rats, propranolol or atropine were given before the venom administration. In the third group the venom was given before the injection of propranolol and atropine in combination. HR was measured by using a cardiotachometer coupler connected to an ECG coupler. MAP was calculated from the recorded arterial blood pressure (ABP) after catheterization of the left common carotid artery. Venom doses of 100 and 200 micrograms/kg produced tachycardia with a dose-response relationship, whereas 400 micrograms/kg evoked sinus tachycardia followed by bradycardia then tachycardia. MAP was elevated after the administration of each dose and reached its maximum value after 60 min with a dose-response relationship. Sinus, atrial and ventricular arrhythmias were observed from the recorded ECG during the time studied. This study revealed that the venom has pressor and depressor effects which are mediated through the autonomic nervous system. Propranolol reduced the stimulatory effects of the highest dose of the venom while atropine was effective in eliminating the depressor effect of the venom on HR. The arrhythmias induced by the venom were blocked by the injection of the two blockers and are assumed to be due to the release of catecholamines and acetylcholine.

Animals↗
PubMed1992

The role of propranolol and atropine in mitigating the toxic effects of scorpion venom on rat electrocardiogram.

The effects of the scorpion Leiurus quinquestriatus (H.&E.) venom on electrocardiogram (ECG) parameters such as P-R and Q-T intervals and R and T wave amplitudes were investigated in anesthetized rats. Venom was administered intramuscularly (i.m.) at three doses (100, 200 and 400 micrograms/kg). ECG limb lead II was recorded for 4-h sessions. Because autonomic nervous system tone plays an important role in influencing ECG findings, another study was completed with concomitant pharmacologic autonomic nervous system blockade. Propranolol or atropine was injected 20 min before venom administration in two groups of rats. The results indicated that the venom has drastic effects on the electrical activity of the heart. The Q-T interval developed a dose-response relationship after venom administration. Propranolol abolished the toxic effects of the venom on P-R and Q-T intervals as well as on R wave amplitude, while atropine had no effect on the ECG changes produced by the venom.

Animals↗
PubMed1994

The effect of dithiothreitol on the activity of tityustoxin from the scorpion Tityus serrulatus venom.

The acetylcholine (ACh) liberating effect on rat brain slices of tityustoxin, an alpha toxin from the scorpion Tityus serrulatus venom, was measured in the absence and presence of dithiothreitol (DTT). The rate of net ACh liberation by toxin concentrations of 2 nmol in 5 ml of organ bath, was 7.5 +/- 0.09 nmol g-1 min-1. If DTT at a final concentration of 1 mM was added after a 10-min incubation period with toxin alone, inhibition of tityustoxin activity was 94%. With DTT 0.1 or 0.01 mmolar inhibition was 74% and 57%, respectively. The intense secretagogue effect, both in salivary and pancreatic glands of adult rats, induced by sublethal doses of tityustoxin was not affected by i.v. injection 10 min later of DTT 1 mumol g-1 of rat weight. When tityustoxin was injected i.p. at a dose 3 times the LD50 in mice, death ensued in 40 to 60 min. If toxin inoculation in mice was followed 10 min later by DTT 1 mumol g-1 of mouse weight, injected i.p. or i.v., deaths were delayed to 90 to 110 min, but no survival was observed. At necropsy, none of the mice treated with DTT showed any signs of pulmonary edema.

Acetylcholine↗
PubMed1995

Effects of toxin Ts-gamma and tityustoxin purified from Tityus serrulatus scorpion venom on isolated rat atria.

The effects of toxin Ts-gamma and tityustoxin purified from Tityus serrulatus scorpion venom were investigated on isolated rat atria. Rat atria were placed in an organ bath containing Krebs-Ringer solution, 30 degrees C, pH 7.4, and bubbled with a gas mixture of 95% O2 and 5% CO2. The atrial rate and contractile force were simultaneously recorded. Addition of toxin Ts-gamma to the bath (0.14 microM) evoked an initial reduction of both atrial rate and contractile force, followed by a small increase in force and a decrease in rate, and finally a long reduction of rate and force. Addition of an identical dose of Ts-gamma 30 or 60 min later did not evoke any effect. Addition of tityustoxin to the bath (0.14 microM) induced an increase of atrial rate and force. Addition of an identical dose of tityustoxin 30 min later evoked similar effects. The negative chronotropic and inotropic effects induced by Ts-gamma were abolished by tetrodotoxin (TTX, 1 microM) or atropine (1.5 microM), whereas the positive effects observed in the presence of atropine were prevented by TTX (1 microM) or alprenolol (10 microM). The negative chronotropic effect of 0.14 microM tityustoxin was only observed in the presence of physostigmine (0.3 microM). This negative effect was abolished by TTX (1 microM) or atropine (1.5 microM). The positive inotropic effect of tityustoxin was decreased by TTX (1 microM and 10 microM), but was totally prevented by guanethidine (10 microM) or alprenolol (10 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1995

Topology of the pore-region of a K+ channel revealed by the NMR-derived structures of scorpion toxins.

The architecture of the pore-region of a voltage-gated K+ channel, Kv1.3, was probed using four high affinity scorpion toxins as molecular calipers. We established the structural relatedness of these toxins by solving the structures of kaliotoxin and margatoxin and comparing them with the published structure of charybdotoxin; a homology model of noxiustoxin was then developed. Complementary mutagenesis of Kv1.3 and these toxins, combined with electrostatic compliance and thermodynamic mutant cycle analyses, allowed us to identify multiple toxin-channel interactions. Our analyses reveal the existence of a shallow vestibule at the external entrance to the pore. This vestibule is approximately 28-32 A wide at its outer margin, approximately 28-34 A wide at its base, and approximately 4-8 A deep. The pore is 9-14 A wide at its external entrance and tapers to a width of 4-5 A at a depth of approximately 5-7 A from the vestibule. This structural information should directly aid in developing topological models of the pores of related ion channels and facilitate therapeutic drug design.

Amino Acid Sequence↗
PubMed2005

Expression of the standard scorpion alpha-toxin AaH II and AaH II mutants leading to the identification of some key bioactive elements.

The AaH II toxin from the scorpion Androctonus australis Hector is considered to be the standard alpha-toxin because it selectively binds with the highest known affinity to site 3 of mammalian voltage-activated Na+ channels (Na(v)) on rat brain synaptosomes but does not bind to insect synaptosomes. We generated two different constructs in pMALp allowing us to produce AaH II fused with the maltose-binding protein (MBP) in E. coli. We obtained reasonable amounts of recombinant AaH II after cleavage by enterokinase at the site DDDDK. We show that the introduction of a net negative charge at the C-terminus by the suppression of H64 amidation and the addition of an extra residue to the C-terminus (G65) led to fully active AaH II mutants, exhibiting exactly the same affinity as the native toxin for its target on rat brain synaptosomes. In contrast, the mutation of residue K58 into V, I or E residues drastically reduced toxin activity.

Amino Acid Sequence↗
PubMed2003

Antimicrobial peptides from scorpion venom induce Ca(2+) signaling in HL-60 cells.

Parabutoporin (PP) and opistoporin 1 (OP1) are amphipathic alpha-helical antimicrobial peptides that were recently isolated from scorpion venom. In assays in which single granulocyte-like HL-60 cells as well as cells in suspension were used, both peptides were able to induce a reversible Ca(2+) release from intracellular stores and to increase Ca(2+) influx. Both effects could be clearly differentiated for OP1, inducing Ca(2+) release at lower concentrations. The Ca(2+) release was pertussis toxin-sensitive indicating the involvement of G-proteins. Ca(2+) release depended on the stage of differentiation of the cells with undifferentiated cells being the most sensitive. Desensitization occurred with OP1. No cross-desensitization occurred between OP1 and the bacterial chemoattractant fMLP indicating the involvement of different types of receptors. Ca(2+) release by OP1 was found not to be mediated via interaction with the formyl peptide receptor-like 1. Although some of the results might favor a receptor-like interaction, the receptor involved could not be identified.

Antimicrobial Cationic Peptides↗
PubMed2004

Antibiotic activity and structural analysis of the scorpion-derived antimicrobial peptide IsCT and its analogs.

IsCT is a non-cell-selective antimicrobial peptide isolated from the scorpion Opisthacanthus madagascariensis that has potent cytolytic activity against both mammalian and bacterial cells. To investigate the structure-activity relationships of IsCT and to design novel peptide antibiotics with bacterial cell selectivity, we synthesized several analogs of IsCT and determined their three-dimensional structures in solution by 2D-NMR spectroscopy. IsCT has a linear alpha-helical structure from Gly3 to Phe13, and [K7]-IsCT has a linear alpha-helical structure from Leu2 to Phe13. [K7, P8, K11]-IsCT, which has a bend in its middle region, exhibited the highest antibacterial activity without hemolytic activity, suggesting that its proline-induced bend is an important determinant of this selectivity. Tryptophan fluorescence showed that the high selectivity of [K7, P8, K11]-IsCT toward bacterial cells is closely correlated with its highly selective interaction with negatively charged phospholipids. Its potent activity against antibiotic-resistant bacteria suggests that [K7, P8, K11]-IsCT may serve as a promising lead candidate in the development of new peptide antibiotics.

Amino Acid Sequence↗