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8.B.2 The Short Scorpion Toxin (S-ST) Family

K+ channel toxin kappa Ktx1.1 of the Indian black scorpion slows the activation kinetics of Kv1.3 currents, and blocks Kv1.3 and Kv1.2 potassium channels. This block is dose-dependent, voltage-independent, and reversible. This toxin has no effect on Kv1.1 currents (Srinivasan et al., 2002).  This family includes Pfam family Toxin_31 (TC# 8.B.2.1) and Toxin_25 (TC# 8.B.2.2).

The 16 aa peptide is amidated and contains a disulfide bridge. It belongs to the K+ channel inhibitor kappa KTx family within the short scorpion toxin family. Another such toxin, K+ channel toxin α-KTx11.3/Parabutoxin-10) binds and inhibits voltage-sensitive potassium channels. It inhibits the vertebrate potassium channel Kv1.1 with low affinity. It shows a region of 26 aas with 46% identity with γ-2 purothionin from wheat (TC #1.C.45.1.3).

This family belongs to the: Defensin Superfamily.

References associated with 8.B.2 family:

Huys, I., Olamendi-Portugal, T., Garcia-Gomez, B.I., Vandenberghe, I., Van Beeumen, J., Dyason, K., Clynen, E., Zhu, S., van der Walt, J., Possani, L.D., and Tytgat, J. (2004). A subfamily of acidic α-K+ toxins. J. Biol. Chem. 279: 2781-2789. 14561751
Peigneur, S., Y. Yamaguchi, H. Goto, K.N. Srinivasan, P. Gopalakrishnakone, J. Tytgat, and K. Sato. (2013). Synthesis and characterization of amino acid deletion analogs of κ-hefutoxin 1, a scorpion toxin on potassium channels. Toxicon 71: 25-30. 23726856
Srinivasan, K.N., Sivaraja, V., Huys, I., Sasaki, T., Cheng, B., Kumar, T.K., Sato, K., Tytgat, J., Yu, C., San, B.C., Ranganathan, S., Bowie, H.J., Kini, R.M., and Gopalakrishnakone, P. (2002). Kappa-Hefutoxin1, a novel toxin from the scorpion Heterometrus fulvipes with unique structure and function. Importance of the functional diad in potassium channel selectivity. J. Biol. Chem. 277: 30040-30047. 12034709