Stromatoxin 1 (ScTx1)

Stromatoxin-1 inhibits with high affinities Kv2.1 and Kv2.2, that encode delayed K+ channels (respectively, with IC50 of 12 and 21 nM). The block is voltage-dependent and slowly reversible. It is also a very sensitive inhibitor of Kv4.2, that encodes a transient K+ current (IC50 of 1.2 nM). Here also, the block is voltage-dependent indicating that ScTx-1 acts as a gating modifier rather than a pore blocker. Reversibility is faster on Kv4.2 channels. In contrast, ScTx-1 has no effect on Kv1.1, Kv1.2, Kv1.3, Kv1.4, Kv1.5, Kv1.6 or Kv3.4 channels.