Babycurus-toxin 1 (BcTx1) is a component of the venom of the east African scorpion ''Babycurus centrurimorphus''. This toxin modifies both the activation and the inactivation properties of insect

sodium channel Sodium channels are integral membrane proteins that form ion channels, conducting sodium ions (Na+) through a cell's membrane. They belong to the superfamily of cation channels and can be classified according to the trigger that opens the channel ...

Sources

This toxin is a component of the venom secreted by the east African scorpion ''Babycurus centrurimorphus'' of the scorpion family

Buthidae The Buthidae are the largest family of scorpions, containing about 100 genera and 1339 species as of 2022. A few very large genera (''Ananteris'', ''Centruroides'', '' Compsobuthus'', or '' Tityus'') are known, but a high number of species-poor o ...

, and is more specific in envenoming insects, for example the cockroach, than in human envenoming.Action of babycurus-toxin 1 from the east African scorpion Babycurus centrurimorphus on the isolated cockroach giant axon
; Ben Khalifa R. Stankiewicz M. Pelhate M. Serrano-Hernandez S.E. Possani L.D. Hinkel H. Mebs D.; Toxicon 35:1069-1080(''1997'')

Chemistry

The molecular weight of BcTx1 is 3248. It belongs to the long (4 C-C) scorpion toxin superfamily and can be classified as a β-toxin. Only the first 30 amino acids of the BcTx1 protein have yet been sequenced. The toxin shares similarities in

protein structure Protein structure is the three-dimensional arrangement of atoms in an amino acid-chain molecule. Proteins are polymers specifically polypeptides formed from sequences of amino acids, the monomers of the polymer. A single amino acid monomer ma ...

with other toxins found in scorpions in North Africa and the Middle East, including the genera ''

Buthus ''Buthus'' is a genus of scorpion belonging and being eponymous to the family Buthidae. It is distributed widely across northern Africa, including Morocco, Mauritania, Algeria, Tunisia, Libya, Egypt, Senegal, Guinea-Bissau, Nigeria, Sudan, Somali ...

'' and ''

Centruroides ''Centruroides'' is a genus of scorpions of the family Buthidae. Several North American species are known by the common vernacular name bark scorpion. Numerous species are extensively found throughout the southern United States, Mexico, Centra ...

''.

Target

The toxin acts affects sodium channel properties. The toxin can bind to many different sodium channels, including mammalian channels, although the effects on non-insect sodium channels have not yet been tested.

Mode of action

BcTx1 acts on insect axonal sodium channels by lowering their activation threshold (by 5-10 mV), resulting in an increase of Na+ conductances. It also shifts the steady-state inactivation curve in the negative direction (by ~15 mV). In addition, BcTx1 slows down the activation of sodium channels. As a result of its action on the sodium channels, neurons depolarize and can no longer fire action potentials, leading to a flaccid paralysis.

References

{{reflist Ion channel toxins Neurotoxins