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:
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.
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.
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.
Examples:
TC#	Name	Organismal Type	Example
8.B.2.1.1	*The K⁺ channel toxin kappa-KTx1.1 (κ-hefutoxin 1.1) of 22 aas (Srinivasan et al., 2002; Peigneur et al.* 2013).**	Animals (Scorpions)	*Toxin kappa KTx1.1 of Heterometrus fulvipes* (P82850)**

8.B.2.1.2	K⁺ channel toxin kappa-KTx1.4 of 62 aas	Animals	Toxin kappa-KTx1.4 of Heterometrus petersii (Asian forest scorpion)

8.B.2.1.3	kappa-KTx-like peptide k-KTxpcavC10 of 69 aa		*kappa-KTx-like peptide k-KTxpcavC10 of Pandinus cavimanus* (Tanzanian red clawed scorpion)**

8.B.2.1.4	Potassium channel toxin kappa-KTx 3.1 of 64 aa		Potassium channel toxin kappa-KTx 3.1 of Heterometrus petersii

Examples:
TC#	Name	Organismal Type	Example
8.B.2.2.1	*The K⁺ channel toxin α KTx11.3 (Huys et al., 2004)*	Scorpions	*Toxin α KTx11.3 of Parabuthus granulatus* (36 aas; Q6WGI9)**

8.B.2.2.2	Disulfide bond-forming potassium channel-impairing neurotoxin of 65 aas.		*Toxin of Lychas mucronatus* (Chinese swimming scorpion)**

8.B.2.2.3	Potassium channel toxin of 64 aa		K⁺ channel blocker of Hemiscorpius lepturus