Selectively and irreversibly binds (K(d)=2.9 pM) and blocks Kv1.3/KCNA3 potassium channels of human T-lymphocytes. Weakly blocks Kv1.2/KCNA2 (9%). Expressed by the venom gland. Has the structural arrangement of an alpha-helix connected to antiparallel beta-sheets by disulfide bonds (CS-alpha/beta). Does not block hKCa3.1/KCNN4, and mKv1.1/KCNA1 channels (Ref.1). Has been patented as lead compound, candidates for the treatment of various autoimmune diseases and diagnostic applications (Ref.1). Belongs to the short scorpion toxin superfamily. Potassium channel inhibitor family. Alpha-KTx 23 subfamily.