Parabutoxin (PBTx) is a Shaker-related voltage-gated K+ channel (Kvα1) inhibitor purified from different Parabuthus scorpion species found in southern Africa.
Four different acidic peptides (PBTx1, PBTx2, PBTx3 and PBTx10) have been isolated and cloned from the venoms of three different Parabuthus scorpion species found in southern Africa.
PBTx3 has a mass of 4274 Da and consists of 37 amino acid residues with a well-conserved three-dimensional structure, stabilized by three disulphide bridges.
[1] These channels have different functions that include regulating neurotransmitter release, heart rate, insulin secretion, neuronal excitability, epithelial electrolyte transport, smooth muscle contraction and cell volume.
Experiments with a recombinant PBTx show a concentration dependency that suggests that the channel is blocked by a single peptide.