A toxin to nervous, cardiac, and endocrine ERG K+ channels isolated from Centruroides noxius scorpion venom

Toxins isolated from a variety of venoms are tools for probing the physiolo gical function and structure of ion channels. The ether-a-go-go-related gen es (erg) codify for the K+ channels (ERG), which are crucial in neurons and are impaired in human long-QT syndrome and Drosophila 'seizure' mutants. W e have isolated a peptide from the scorpion Centruroides noxius Hoffmann th at has no sequence homologies with other toxins, and demonstrate that it sp ecifically inhibits (IC50=16+/-1 nM) only ERG channels of different species and distinct histogenesis. These results open up the possibility of invest igating ERG channel structure-function relationships and novel pharmacologi cal tools with potential therapeutic efficacy.