Psalmotoxin (PcTx1) is a spider toxin from the venom of the Trinidad tarantula Psalmopoeus cambridgei. The psalmotoxin structure can be classified as an inhibitor cystine knot (ICK) protein. Many ion channel effectors from snail, spider, and scorpion venoms share a similar ICK structure, although they possess very different pharmalogical profiles. Among ICK toxins, psalmotoxin is the only peptide known to act on homomeric ASIC1 channels. Psalmotoxin is a 40-amino acid peptide, possessing 6 cysteines linked by three disulfide bridges. The three-dimensional structure consists of a compact disulfide-bonded core from which three loops and the N and C termini emerge. The main element of the structure is a three-stranded antiparallel β-sheet. Psalmotoxin can bind to a particular isoform of the Acid Sensing Ion Channel, the Acid Sensing Ion Channel 1 (ASIC1).
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