Ion-channels formed by hypelcins, antibiotic peptides, in planar bilayer lipid membranes

Ion-channel properties of native hypelcins (HP) A-I, A-V and B-V isolated from Hypocrea peltata and a synthetic analog, HP-A-Pheol, were studied in planar bilayer lipid membranes by a single-channel recording technique. The native and synthetic hypelcins formed ion-channels with three conductance levels for 3 mole dm(-3) KCl: less than or equal to 0.09 nS at 225 mV (level 0, only detectable at voltages above 200 mV), approximate to 0.6 nS at 150 mV (level 1, most common level) and approximate to 3 nS at 150 mV (level 2). The effects of the C-terminal aminoalcohol on the channel properties were examined with KP-A-I, HP-A-V and HP-A-Pheol, whose C-termini are leucinol (Leuol), isoleucinol (Ileol) and phenylalaninol (Pheol), respectively. The substitution of Pheol for Leuol and Ileol prolonged the open channel lifetime. A comparison of HP-A-V (Gln18) and HP-B-V (Glu18) indicated that the carboxyl group at position is increased both the open channel lifetime and the magnitude of unitary channel conductance at each conductance level. The pores of level 1 showed poor ion-selectivity for K+ over Cl-. The selectivity order of alkali metal cations was Rb greater than or equal to Cs greater than or equal to K > Na > Li for level 1 and Cs > Rb > K > Na > Li for level 0. The unitary current-voltage characteristics showed non-linear relationships, which were simulated by a Nernst-Planck approach with a simple barrier model.