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: < or = 0.09 nS at 225 mV (level 0, only detectable at voltages above 200 mV), approximately 0.6 nS at 150 mV (level 1, most common level) and approximately 3 nS at 150 mV (level 2). The effects of the C-terminal aminoalcohol on the channel properties were examined with HP-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 18 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 > or = Cs > or = 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.
Koide
N
N
Institute for Chemical Research, Kyoto University, Uji, Japan.
Asami
K
K
Fujita
T
T
D000408:Alamethicin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D007473:Ion Channels / Q000032:analysis*; D008051:Lipid Bilayers / Q000737:chemistry*; D008969:Molecular Sequence Data
D000900:Anti-Bacterial Agents; D007473:Ion Channels; D008051:Lipid Bilayers; D000408:Alamethicin; C025478:hypelcin A; C025479:hypelcin B