Margatoxin

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

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.