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Margatoxin (MgTx) is a Kv1.3 voltage-dependent potassium channel-blocking toxic peptide found in the venom of the South American scorpion Centruroides margaritatus.

Contents

Source

Centruroides margaritatus is also known as the Central American bark scorpion. It is native to Central and South America. Typical examples are 5-8 cm long, including the tail.

Chemistry

The amino acid sequence is:

H-Thr-Ile-Ile-Asn-Val-Lys-Cys-Thr-Ser-Pro-Lys-Gln-Cys-Leu-Pro-Pro-Cys-Lys-Ala-Gln-Phe-Gly-Gln-Ser-Ala-Gly-Ala-Lys-Cys-Met-Asn-Gly-Lys-Cys-Lys-Cys-Tyr-Pro-His-OH (Disulfide bonds between Cys7-Cys29, Cys13-Cys34 and Cys17-Cys36).

The molecular formula is C178H286N52O50S7 and the molecular weight is 4179.0.

Target

Margatoxin is a specific blocker for Kv1.3 potassium channels.

Mode of action

Margatoxin blocks Kv1.3 channels specifically with high chemical affinity (picomolar concentrations) as a peptidyl inhibitor. These channels play a key role in neurotransmitter release. Blocking these channels results in a loss of outward current.

Toxicity

The median lethal dose (LD50) of margatoxin is 59.9 mg/kg, so Centruroides margaritatus stings are not dangerous to humans except as a result of possible anaphylactic responses. They do cause pain, local swelling and tingling for 3–4 hours, but no intervention beyond symptomatic relief should be necessary.

References

  • Knaus HG, Koch RO, Eberhart A, Kaczorowski GJ, Garcia ML, Slaughter RS.[125I]margatoxin, an extraordinarily high affinity ligand for voltage-gated potassium channels in mammalian brain. Biochemistry. 1995 Oct 17;34(41):13627-34.
  • Garcia-Calvo M, Leonard RJ, Novick J, Stevens SP, Schmalhofer W, Kaczorowski GJ, Garcia ML. Purification, characterization, and biosynthesis of margatoxin, a component of Centruroides margaritatus venom that selectively inhibits voltage-dependent potassium channels. J Biol Chem. 1993 Sep 5;268(25):18866-74.
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