Purification of protein toxins from Leiurus Quinquestriatus Hebraeus that modify Na channels
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Toxins were purified from crude venom obtained from Middle Eastern scorpions, Leiurus cruinouestriatus hebraeus (Lqh). Active fractions were purified using cationic exchange chromatography, and tested for their ability to lengthen and attenuate propagated compound action potentials (C.A.P.) recorded from frog sciatic nerves using the sucrose-gap technique. The most active purified toxin was tested for its ability to modify Na channels using the frog skeletal muscle vaseline-gap voltage-clamp. Using a two-step purification scheme, two fractions, from Leiurus quinauestriatus hebraeus containing toxins (Lqhl and Lqh2), absorbing at 280 nM, were found to be active in prolonging and attenuating the C.A.P. The two fractions were tested and compared to toxin V (Lqq5) from Leiurus quinauestriatus quinauestriatus (Lqq) obtained from North African scorpions. Lqhl and Lqh2 were purified to homogeniety and possessed molecular weights of 6390 and 5870 Daltons respectively; thus both toxins differ in size from Lqq5 (7462). Electrophysiological experiments suggested that three toxins are different. Both toxins, Lqhl and Lqh2, exhibited greater potency than Lqq5. Evidence from sucrose-gap and voltage-clamp experiments suggests that all three toxins act in a voltage-dependent fashion to bind to Na channels and block them, besides their well known ability to modify inactivation kinetics.