8.B.26 The Scorpion Toxin, Scoloptoxin (Scoloptoxin) Family
The Scoloptoxin family includes a number of peptide/protein toxins of vaious sized that bind to and inhibit various Na+ and K+ channels of the VIC superfamily (1.A.1). For example, κ-scoloptoxin, Ssm1a, inhibits voltage-gated potassium channel currents in DRG neurons with an IC50 of 44.2 nM and shows signs of neurotoxicity including twitching, paralysis, and body contractions (Yang et al. 2012), and the 47 aa centipede toxin, Ssd609, inhibits K+ currents by binding to KCNE1 (8.A.10.1.1), a single-span transmembrane auxiliary protein that modulates the voltage-gated potassium channel KCNQ1 (TC# 1.A.1.15.1 and 1.A.1.15.6). The KCNQ1/KCNE1 complex in cardiomyocytes exhibited slow activated potassium (Iks) currents (Sun et al. 2015). Another centipede toxin, SsmTx-I acts as a simple inhibitor or channel blocker rather than a gating modifier of at least 9 channels including Kv2.1 (TC# 1.A.1.2.11) (Chen et al. 2014). The high resolution structures of several of these toxins are known.