BUY Psalmotoxin-1

Psalmotoxin-1. A Potent Blocker of ASIC 1a Channels.

Native Psalmotoxin-1 (PcTx-1) is a 40 amino acid toxin originally isolated from the venom of the South American tarantula Psalmopoeus cambridgei.
PcTX-1 is characterized by the unusual quadruplet Lys²⁵-Arg²⁶-Arg²⁷-Arg²⁸, which probably forms a strongly positive "patch" at the surface of the toxin molecule, constituting an area that is a strong candidate for channel binding site recognition. The molecular scaffold of PcTX-1 is likely to be similar to that previously described for both cone snail and spider toxins and comprises a triple-stranded antiparallel beta-sheet structure reticulated by three disulfide bridges.

PcTx-1 potently (IC-₅₀�=�0.9�nM) and specifically blocks a particular subclass of H⁺-gated cation channels, the Acid-sensing ion channels 1a (ASIC1a) and is able to discriminate between the two splice variant subtypes and not block the ASIC1b channel (which differs only in its N-terminal sequence). Moreover PcTX-1 loses its capacity to block ASIC1a as soon as this subunit is associated with another member of the family (ASIC2a or ASIC3).
The ASICs are abundant in the brain and spinal cord neurons and are implicated in pain sensation, ischemic stroke mechanosensation, learning and memory.
In acute and neuropathic pain models, specific blockage of ASIC1a with PcTx-1 results in analgesic effects working upstream of the opiate receptors.
Using an iodinated form of the toxin, the binding for the PcTX-1 site identifies at the cysteine-rich domains I and II (CRDI and CRDII) of the extracellular loop of ASIC1a. A Disulphide bridge between domains 1 and 4 of the channel supports a close relationship between the CRDI4�CRDII domain, where PcTx-1 acts, and the post-M1 region, the binding site for the proton.

Ion Channel Modulators; ASIC Channel Blockers.