Charybdotoxin is a new member of the K sup + channel toxin family that includes dendrotoxin I and mast cell degranulating peptide
- Universite de Nice (France)
- Institut Pasteur de Lille (France)
A polypeptide was identified in the venom of the scorpion Leiurus quinquestriatus hebraeus by its potency to inhibit the high affinity binding of the radiolabeled snake venom toxin dendrotoxin I ({sup 125}I-DTX{sub I}) to its receptor site. It has been purified, and its properties investigated by different techniques were found to be similar to those of MCD and DTX{sub I}, two polypeptide toxins active on a voltage-dependent K{sup +} channel. However, its amino acid sequence was determined, and it was shown that this toxin is in fact charybdotoxin (ChTX), a toxin classically used as a specific tool to block one class of Ca{sup 2+}-activated K{sup +} channels. ChTX, DTX{sub I}, and MCD are potent convulsants and are highly toxic when injected intracerebroventricularly in mice. Their toxicities correlate well with their affinities for their receptors in rat brain. These three structurally different toxins release ({sup 3}H)GABA from preloaded synaptosomes, the efficiency order being DTX{sub I} > ChTX > MCD. Both binding and cross-linking experiments of ChTX to rat brain membranes and to the purified MCD/DTX{sub I} binding protein have shown that the {alpha}-subunit of the MCD/DTX{sub I}-sensitive K{sup +} channel protein also contains the ChTX binding sites. Binding sites for DTX{sub I}, MCD, and ChTX are in negative allosteric interaction. The results show that charybdotoxin belongs to the family of toxins which already includes the dendrotoxins and MCD, which are blockers of voltage-sensitive K{sup +} channels. ChTX is clearly not selective for Ca{sup 2+}-activated K{sup +} channel.
- OSTI ID:
- 7138149
- Journal Information:
- Biochemistry; (USA), Vol. 28:25; ISSN 0006-2960
- Country of Publication:
- United States
- Language:
- English
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IODINE 125
CROSS-LINKING
NEUROREGULATORS
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MOLECULAR STRUCTURE
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PEPTIDES
POLYPEPTIDES
POTASSIUM COMPOUNDS
PURIFICATION
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DRUGS
ELECTRON CAPTURE RADIOISOTOPES
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INTERMEDIATE MASS NUCLEI
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NUCLEI
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550201* - Biochemistry- Tracer Techniques