Blocker for the small conductance calcium-activated potassium channels (PubMed:2839478, PubMed:2307683, PubMed:11527975). Shows the best affinity for KCa2.2/KCNN2 (Kd=0.2 nM), followed by KCa2.3/KCNN3 (Kd=1.1 nM) and KCa2.1/KCNN1 (Kd=325 nM) (PubMed:11527975). Expressed by the venom gland. Has the structural arrangement of an alpha-helix connected to a beta-sheet by disulfide bonds (CSalpha/beta). Two disulfide bonds are the minimal requirement needed to produce a nativelike and bio-active conformation in this toxin. The third disulfide provides an additional contribution to structure stabilization and can modulate biological potency depending on its position and the structural regions involved in biological activity. A mutant [R7diaminobutanoic acid] has been developed that discriminates KCa2.2/KCNN2 (Kd=3.8 nM) from KCa2.3/KCNN3 (Kd=2500 nM). Belongs to the short scorpion toxin superfamily. Potassium channel inhibitor family. Alpha-KTx 05 subfamily.