Pardaxin: channel formation by a shark repellant peptide from fish.

The results of the various studies describing the mechanism involved in pore formation by pardaxin and some of its analogues, support a 'barrel-stave' model (Ehrenstein amd Lecar, 1977). In this model pardaxin exerts its activity via three successive steps: (i) a fast binding step (as reflected by the rapid increase of NBD fluorescence in the presence of vesicles); (ii) insertion of peptides into the lipid bilayer; and (iii) the monomers aggregate into a barrel-like formation in which a central aqueous pore surrounded by proteins is formed. This pore increases in diameter through the progressive recruitment of additional monomers. Both the fluorescence energy transfer (FET) studies and the observation of a significant difference in the increase of NBD fluorescence, depending on which terminal was labelled by the fluorophore, support a model by which aggregates are formed in an ordered parallel manner, where the C-terminus is more exposed to the aqueous phase.