Margatoxin

Margatoxin (MgTx) is a toxin from the South American scorpion Centruroides margaritatus, which blocks Kv1.3 voltage-dependent potassium channels.

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Source

Centruroides margaritatus also known as the Central American bark scorpion. This is a scorpion that is native to Central and South America. It is from a big scorpion family (Centuroides). They are about 5-8 cm long, including their tail.

Chemistry

Its 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)

Its molecular formula is C178 H286 N52 O50 S7

Its molecular weight is 4179.0

Target

Margatoxin is a specific blocker for the Kv1.3 channel, which is a subtype of 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

Centruroides margaritatus is not deadly but has a painful sting that causes local swelling and tingling. This means that if the scorpion stings you, the pain will be gone in 3-4 hours. The LD50 is 59.9 mg/kg, so a lot of scorpion venom should be injected to actually cause any damage to human. No extra treatment will be needed. Anti-histamines might be suited to prevent an allergic response.

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.

• Kupper J, Prinz AA, Fromherz P. Recombinant Kv1.3 potassium channels stabilize tonic firing of cultured rat hippocampal neurons. Pflugers Arch. 2002 Feb;443(4):541-7. Epub 2001 Oct 18.

• http://www.axxora.com/toxins-ALX-630-045/opfa.1.1.ALX-630-045.1879.4.1.html