Kappa-stichotoxin-Shd1a: inhibits voltage-gated potassium channels (Kv). Kappa-stichotoxin-Shd1b: inhibits voltage-gated potassium channels (Kv). This toxin inhibits the binding of 125I-alpha-dendrotoxin to synaptosomal membranes (IC(50)=270 nM). Occurs in 2 forms which differ in the post-translational modification of Pro-6. In form SHTX-1 (Shd1a) Pro-6 is a hydroxyproline while in form SHTX-2 (Shd1b) Pro-6 is unmodified. PD(50) of SHTX-1 (Shd1a) and -2 (Shd1b) are 430 ug/kg into crabs. Belongs to the sea anemone structural class 9a family.