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FTX-3.3 is the proposed structure of a calcium-channel blocking toxin that has been isolated from the funnel web spider (Agelenopsis aperta). The effects of FTX-3.3 and one of its analogues, sFTX-3.3, on acetylcholine release, on presynaptic currents at mouse motor nerve terminals and on whole-cell sodium currents in SK.N.SH cells (a human neuroblastoma cell line) have been studied. FTX-3.3 (10-30...
Green and black mamba snake venoms contain small proteins that bind to muscarinic receptors (Jeralinsky and Harvey, 1994; Kornisiukl et al., 1995). MT x 1 and MT x 2 from Eastern green mamba (Dendroaspis angusticeps) venom inhibit the binding of the muscarinic antagonist 3 H-NMS to synaptosomal membranes of different brain regions. They also inhibit the binding of 3 ...
Potassium channel toxins are small proteins isolated from venoms of snakes, scorpions, sea anemones and bees, which specifically block potassium-selective ion channels in cell membranes. The effects of the toxins were first discovered in the early 1980s, with the characterization of apamin from bee venom, charybdotoxin and noxiustoxin from different scorpions, and the dendrotoxins from mamba snakes...
Dendrotoxins are 57-60 residue proteins isolated from venoms of mamba snakes, Dendroaspis angusticeps, D. polylepis and D. viridis. They are related to Kunitz-type inhibitors of serine proteases. Six natural variants have been sequenced: two isoforms of α-dendrotoxin and δ-dendrotoxin from D. angusticeps, toxin I and toxin K fromD. polylepis , and Dv 14 from D. viridis. Two related toxins, β- and...
For many years sea anemones have constituted a source of neuroactive compounds mainly modifying kinetic aspects of sodium channels. In addition, potassium channel blocking activity has been discovered in the aqueous extract of Stichodactyla helianthus and Bunodosoma granulifera (Karlsson et al., 1991), and recently two potassium channel blockers have been isolated: BgK (Aneiros et al., 1993) and...
Previous studies have shown that homologous phospholipases A 2 (PLA 2 ) (Pa-3, Pa-9C, Pa-10F and Pa-11) from the venom of the Australian king brown snake, Pseudechis australis, significantly reduce the resting membrane potentials and quantal contents of endplate potentials recorded from endplate regions of mouse triangularis sterni nerve-muscle preparations. It is not clear whether...
The effect of diamide, a thiol-oxidizing agent, was tested using electrophysiological techniques to determine whether its ability to alter neuromuscular transmission in vitro could be attributed to alterations of ion channels controlling neuronal excitability and/or acetylcholine release. In mouse triangularis sterni preparations, diamide transiently increased the evoked release of acetylcholine...
The effects of the venom of the Sahara sand viper (Cerastes vipera) were studied on isolated chick biventer cervicis, isolated rat atria and vas deferens preparations, and on the electrocardiogram of anaesthetized rats. Effects on 3 H-noradrenaline uptake were studied using rat brain synaptosomes. At 50 μg/ml and 100 μg/ml, the venom caused a transient increase in rate and force of contractions...
Scorpion venoms contain toxins that block different types of potassium channels. Some of these toxins have affinity for high conductance Ca 2+ -activated K + channels and for dendrotoxin-sensitive voltage-dependent K + channels. The structural features that determine the specificity of binding to different channel types are not known. We investigated this using natural...
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