The solution structure of BmTX2 purified from the venom of the Chinese Buthid
Buthusmartensi has been determined by 2D NMR spectroscopy techniques which led to the description of its3D conformation. The structure consists of a triple-stranded
![](/images/gifchars/beta2.gif)
-sheet connected to a helical structure.This helix encompasses 10 residues, from 11 to 20, begins with a turn of 3
10 helix, and ends with an
![](/images/gifchars/alpha.gif)
helix. The three strands of
![](/images/gifchars/beta2.gif)
sheet comprise residues 2-6, with a bulge covering residues 4 and 5,26-29, and 32-35, with a type I'
![](/images/gifchars/beta2.gif)
turn centered on residues 30-31. We also characterized the solutionstructure of BmTX1. The two toxins which are potent blockers of both large-conductance calcium-activated potassium channels (BK
Ca channels) and voltage-gated potassium channels (Kv1.3) are highlysuperimposable and possess the same structural characteristics. Analysis of these structures allows us tohypothesize that, besides the main surface of interaction described by the functional map of charybdotoxin,one can expect that the binding of scorpion toxins on BK
Ca channels may involve residues on the edgeof this surface.