The functional face of “short-chain” scorpion toxins is built of two important dyads (Lys and Tyr) on the β-sheet side. Lysine plugs deep into the channel pore and Tyrosine, as penultimate or ultimate and hydrophobic residue, turns it to fixate it, leading to a physical occlusion of the channel pore. This is supported by the finding that deletion of the two C-terminal residues (sBmTx3-delYP) results in loss of ability to block IA-current.
