查看文章

Tityus kappa (Ts κ), a novel toxin from the venom of the scorpion Tityus serrulatus, is a 35‐residue polypeptide cross‐linked by three disulphide bridges and acts on small‐conductance calcium‐activated potassium channels (SK channels). Ts κ was chemically synthesized using the solid‐phase method and characterized. The synthetic product, sTs κ, was indistinguishable from the natural toxin when tested in vitro in competition assay with radiolabelled apamin for binding to rat brain synaptosomes (IC₅₀ = 3 nm). The sTs κ was further tested in vivo for lethal activity to mice following intracerebroventricular inoculation (LD₅₀ = 70 ng per mouse). The half‐cystine pairings were formerly established by enzyme‐based cleavage of sTs κ; they were between Cys₇–Cys₂₈, Cys₁₃–Cys₃₃ and Cys₁₇–Cys₃₅, which is a disulphide bridge pattern similar to that of other short scorpion toxins. According to previous …