BeKm-1 toxin

BeKm-1 is a toxin from the Central Asian scorpion

potassium ion channels

.

Etymology

Be is the abbreviation of the scorpion from which the venom is isolated,
Buthus eupeus. Km is an abbreviation of M-type K⁺ current, which is inhibited by the venom.^[1]

Chemistry

BeKm-1 is a 4 kDa peptide consisting of 36
alpha-helix and three beta-strands, arranged in a strongly twisted antiparallel beta sheet, compactly fold up. The helix is confined by two ‘caps’ that have also been described in other short scorpion toxins.^[3]

BeKm-1 shows structural homology to the family of scorpion venom potassium channel blockers, the α-KTx family. Despite the similarities between BeKm-1 and these scorpion toxins, BeKm-1 belongs to a new subfamily of scorpion K1 channel blocking peptides. The differences between the subfamilies are in the COOH-terminal part: the newly described family of toxins, BeKm-1 included, contains Arg 17, Val 29 and Phe32, while the older one Lys, Met and Lys.

Mode of action

BekM-1 selectively inhibits
ECG.^[5]

Toxicity

The
Buthus eupeus
in mice is 1.45 mg/kg.

Treatment

Anti-venom of Androctonus crassicaude can be used in the treatment of

Buthus eupeus scorpion stings.^[6]

References

^ Angelo, K., et al., A radiolabeled peptide ligand of the hERG channel, [125I]-BeKm-1. Pflügers Arch, 2003. 447(1): p. 55-63.
^ Korolkova, Y.V., et al., An ERG channel inhibitor from the scorpion Buthus eupeus. J Biol Chem, 2001. 276(13): p. 9868-76.
^ Korolkova, Y.V., et al., New binding site on common molecular scaffold provides HERG channel specificity of scorpion toxin BeKm-1. J Biol Chem, 2002. 277(45): p. 43104-9.
^ Zhang, M., et al., BeKm-1 is a hERG-specific toxin that shares the structure with ChTx but the mechanism of action with ErgTx1. Biophys J, 2003. 84(5): p. 3022-36.
^ Qu, Y. et al., BeKm-1, a peptide inhibitor of hERG potassium currents, prolongs the QTc intervals in isolated rabbit heart. J Pharmacol Exp Ther, 2011. 337(1): p. 2-8.
^ Ozkan, O. and A. Carhan, The neutralizing capacity of Androctonus crassicauda antivenom against Mesobuthus eupeus scorpion venom. Toxicon, 2008. 52(2): p. 375-9.

[1] Angelo, K., et al., A radiolabeled peptide ligand of the hERG channel, [125I]-BeKm-1. Pflügers Arch, 2003. 447(1): p. 55-63.

[2] Korolkova, Y.V., et al., An ERG channel inhibitor from the scorpion Buthus eupeus. J Biol Chem, 2001. 276(13): p. 9868-76.

[3] Korolkova, Y.V., et al., New binding site on common molecular scaffold provides HERG channel specificity of scorpion toxin BeKm-1. J Biol Chem, 2002. 277(45): p. 43104-9.

[4] Zhang, M., et al., BeKm-1 is a hERG-specific toxin that shares the structure with ChTx but the mechanism of action with ErgTx1. Biophys J, 2003. 84(5): p. 3022-36.

[5] Qu, Y. et al., BeKm-1, a peptide inhibitor of hERG potassium currents, prolongs the QTc intervals in isolated rabbit heart. J Pharmacol Exp Ther, 2011. 337(1): p. 2-8.

[6] Ozkan, O. and A. Carhan, The neutralizing capacity of Androctonus crassicauda antivenom against Mesobuthus eupeus scorpion venom. Toxicon, 2008. 52(2): p. 375-9.

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