CboK7, also known as α-KTx 2.24, is a toxin produced by a species of scorpion, Centruroides bonito. It blocks voltage-gated K+ channels, with the highest affinity for Kv1.2 channels.
| CboK7 | |||||||
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| Identifiers | |||||||
| Symbol | ? | ||||||
| UniProt | C0HM78 | ||||||
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| Identifiers | |
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3D model (JSmol)
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| Properties | |
| C189H302N52O52S7 | |
| Molar mass | 4359.23 g·mol−1 |
| Related compounds | |
Related compounds
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CboK3, CboK4 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Etymology
editThis toxin is known by two names: CboK7 and α-KTx 2.24.[1]
The name CboK7 comes from the species the toxin was found in, C. bonito. K denotes the fact that the toxin affects potassium channels. Seven of these toxins were found in the venom of C. bonito, and this toxin was given the number 7.
The name α-KTx 2.24 is based on another naming system; scorpion toxins that affect potassium channels are referred to as KTx, and further classified with a Greek letter into one of the seven existing subfamilies, with this toxin belonging to the alpha family, which is characterized by a short chain and having three or four disulfide bridges.[1][2]
Chemistry
editFamily
editCentruroides bonito is found in the Mexican state Guerrero. The venom of C. bonito has seven different peptides, CboK1 to CboK7. These seven toxins are part of the α-KTx family (parabutoxin), whose family members have very low pH values.[3]
Structure
editCboK7 consists of 39 amino acid residues and weighs 4,365 Da.[4]
All CboK peptides contain a functional dyad of Lys and Tyr.[1] The functional dyad refers to a pair of amino acid residues in toxins that target Kv1 channels, which plays a key role in toxin-binding. It typically consists of a lysine residue paired with a hydrophobic residue, such as tyrosine, phenylalanine or leucine.[5]
Sequence: TFINVKCTSPKQCLKPCKDLYGPHAGEKCMNGKCKCYKV[4]
Homology
editCboK7 varies from CboK3 and CboK4 by one amino acid. Specifically, CboK7 has Phe instead of Ile in CboK3 and Val instead of Pro in CboK4.[1]
Target & mode of action
editCboK7 toxin affects voltage-gated potassium channels. It is capable of completely blocking Kv1.2 type channels, with a high affinity (Kd = 24 pM), and it can partially inhibit Kv1.1 and Kv1.3 channels with a lower affinity (Kd = 141 nM and 20.4 nM, respectively).[1]
The blocking occurs by the binding of CboK7 to the potassium channel. Specifically, its lysine residue blocks the selectivity filter,[1] which is the part of the channel that is structured in a way that allows only K+ ions to pass through. Blocking this filter prevents the flow of ions through the channel.[6]
The impact of CboK7 on humans has not yet been reported, but the typical symptoms of Centruroides genus venom poisoning are known.[7]
References
edit- ^ a b c d e f Shakeel, Kashmala; et al. (15 August 2023). "Of seven new K+ channel inhibitor peptides of Centruroides bonito, α-KTx 2.24 has a picomolar affinity for Kv1.2". Toxins. 15 (8): 506. doi:10.3390/toxins15080506. PMC 10467108. PMID 37624263.
- ^ "InterPro". www.ebi.ac.uk. Retrieved 2024-10-23.
- ^ "InterPro". www.ebi.ac.uk. Retrieved 2024-10-23.
- ^ a b "UniProt". www.uniprot.org. Retrieved 2024-10-23.
- ^ Mouhat, Stephanie; De Waard, Michel; Sabatier, Jean-Marc (February 2005). "Contribution of the functional dyad of animal toxins acting on voltage-gated Kv1-type channels". Journal of Peptide Science. 11 (2): 65–68. doi:10.1002/psc.630. ISSN 1075-2617. PMID 15635666.
- ^ "Nervous system | Definition, Function, Structure, & Facts | Britannica". www.britannica.com. 2024-09-25. Retrieved 2024-10-23.
- ^ Shamoon, Zafar; Peterfy, Ryan J.; Hammoud, Sami; Khazaeni, Babak (2024), "Scorpion Toxicity", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 28613678, retrieved 2024-10-23