Cytolytic and K+ channel blocking activities of β-KTx and scorpine-like peptides purified from scorpion venoms
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Among the scorpion venom components whose function are poorly known or even show contrasting pharmacological results are those called “orphan peptides”. The most widely distributed are named β-KTx or scorpine-like peptides. They contain three disulfide bridges with two recognizable domains: a freely moving N-terminal amino acid sequence and a tightly folded C-terminal region with a cysteine-stabilized α/β (CS-αβ) motif. Four such peptides and three cloned genes are reported here. They were assayed for their cytolytic, antimicrobial and K+ channel-blocking activities. Two main characteristics were found: the existence of an unusual structural and functional diversity, whereby the full-length peptide can lyse cells or kill microorganisms, and a C-terminal domain containing the CS-αβ motif that can block K+ channels. Furthermore, sequence analyses and phylogenetic reconstructions are used to discuss the evolution of this type of peptide and to highlight the versatility of the CS-αβ structures.