Reversibly and voltage-independently blocks voltage-gated potassium channels rKv1.2/KCNA2 (73%) (IC(50)=196 nM), hKv1.3/KCNA3 (50%) (IC(50)=508 nM), Shaker IR (30%), rKv1.6/KCNA6 (22%) (at 0.5 uM). Interaction of Ts15 with Kv1.3/KCNA3 is stronger than its interaction with Kv1.2/KCNA2. 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 voltage-gated sodium channels rNav1.4/SCN4A, hNav1.5/SCN5A, mNav1.6/SCN8A and rNav1.8/SCN10A, and Kv1.1/KCNA1, rKv1.4/KCNA4, rKv1.5/KCNA5, rKv2.1/KCNB1, hKv3.1/KCNC1, rKv4.2/KCND2, rKv4.3/KCND3 and hERG potassium channels, when tested at a concentration of 0.5 uM. Belongs to the short scorpion toxin superfamily. Potassium channel inhibitor family. Alpha-KTx 21 subfamily. Truncated N-terminus.