Ion release from vesicles induced by pardaxin and its analogues

Abstract The mechanism of pore formation employed by pardaxin, a shark-repellent neurotoxin, and three of its charge-modified analogues, (N 1 ,Lys 8 ,Lys 16 -trisuccinylamido)pardaxin, (N 1 ,Lys 8 ,Lys 16 -triacetyl) pardaxin and (C 33 -di-ethanolamido)pardaxin, was investigated. The kinetics of Tl + and IO 3 − release from large unilamellar phospholipid vesicles was measured under acidic, neutral and basic conditions. Both the kinetics of pore formation and the ability of the analogues to release ions increase when the N-terminal amino acid residue and the peptide backbone are either neutrally or positively charged. Moreover, five- or sixfold higher concentrations of the polypeptides are required for IO 3 − release than for Tl + release. Our results are consistent with the “barrel stave” model by which pardaxin and its analogues exert their pore-forming activities. The smallest pore permeable to Tl + is impermeable to IO 3 − , for which larger pores obtained at higher polypeptide concentrations are required.