8.B.2 The Short Scorpion Toxin (S-ST) Superfamily
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). Belongs to 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 superfamily. 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).