Appearance : white lyophilized solid
Purity rate : > 98%
AA sequence : Asp-Cys2-Thr-Arg-Met-Phe-Gly-Ala-Cys9-Arg-Arg-Asp-Ser-Asp-Cys15-Cys16-Pro-His-Leu-Gly-Cys21-Lys-Pro-Thr-Ser-Lys-Tyr-Cys28-Ala-Trp-Asp-Gly-Thr-Ile-NH2
Disulfide bonds : Cys2-Cys16, Cys9-Cys21 and Cys15-Cys28
Length (aa) : 34
Stromatoxin-1 (ScTx-1) has been isolated from the venom of the African tarentula Stromatopelma calceata.Stromatoxin-1 is a 34 amino-acid long peptide that belongs to the structural family of inhibitor cystine knot peptides reticulated by three disulfide bridges. It has an amidated C-terminus and bears strong homology with hanatoxin 1 (83%).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. Stromatoxin-1 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,Stromatoxin-1 has no effect on Kv1.1, Kv1.2, Kv1.3, Kv1.4, Kv1.5, Kv1.6 or Kv3.4 channels. The toxin has also no effect on voltage-dependent Na+ and Ca2+ channels of cerebellar granule cells. Stromatoxin-1 was found to increase the spontaneous phasic contraction amplitude, muscle force and tone in isolated rat urinary bladder smooth muscle. It also enhances myogenic constriction in pressurized arterial segments.