Margatoxin (MgTX) is a peptide that selectively inhibits Kv1.3 voltage-dependent potassium channels. It was purified from scorpion venom and its amino acid sequence was determined. Margatoxin is a peptide of 39 amino acids with a molecular weight of 4185 Dalton. The primary amino acid sequence of Margatoxin is as follows: 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. There are disulfide bridges between Cys 7-Cys29, Cys13-Cys34 and Cys17-Cys36. Margatoxin is classified as a 'Scorpion short toxin' by Pfam, showing sequence homology with other potassium channel blockers, such as charybdotoxin (44%), kaliotoxin (54%), iberiotoxin (41%) and noxiustoxin (79%), which are also derived from scorpion venom.
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