Three-finger toxin
| Snake toxin and toxin-like protein | |||||||||
|---|---|---|---|---|---|---|---|---|---|
Erabutoxin A, a neurotoxin that is a member of the 3FTx superfamily. The three "fingers" are labeled I, II, and III, and the four conserved disulfide bonds are shown in yellow. Rendered from PDB: 1QKD.
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| Identifiers | |||||||||
| Symbol | Toxin_TOLIP | ||||||||
| Pfam | PF00087 | ||||||||
| Pfam clan | CL0117 | ||||||||
| InterPro | IPR003571 | ||||||||
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| Available protein structures: | |
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| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
Three-finger toxins (abbreviated 3FTx) are a protein superfamily of small toxin proteins found in the venom of snakes. Three-finger toxins are in turn members of a larger superfamily of three-finger protein domains which includes non-toxic proteins that share a similar protein fold. The group is named for its common structure consisting of three beta strand loops connected to a central core containing four conserved disulfide bonds. The 3FP protein domain has no enzymatic activity and is typically between 60-74 amino acid residues long. Despite their conserved structure, three-finger toxin proteins have a wide range of pharmacological effects. Most members of the family are neurotoxins that act on cholinergic intercellular signaling; the alpha-neurotoxin family interacts with muscle nicotinic acetylcholine receptors (nAChRs), the kappa-bungarotoxin family with neuronal nAChRs, and muscarinic toxins with muscarinic acetylcholine receptors (mAChRs).
The three-finger toxin superfamily is defined by a common tertiary structure consisting of three beta strand-containing loops (designated loops I, II, and III) projecting from a small hydrophobic core containing four conserved disulfide bonds. This structure is thought to resemble a hand with three fingers, giving rise to the name. The proteins are typically 60-74 amino acid residues long, though some have additional N- or C-terminal extensions. An additional disulfide bond may be present in either loop I or loop II. The superfamily can be broadly divided into three classes:
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