A lipid vesicle system for probing voltage-dependent peptide-lipid interactions: application to alamethicin channel formation.
A membrane potential is shown to be established in phosphatidylcholine/cholesterol unilamellar vesicles using valinomycin in conjunction with a potassium ion gradient; this potential is monitored using the externally added fluorescent dye Safranine O. In the same system, transmembrane calcium fluxes are then detected using the (internally trapped) fluorescent dye Quin-2. The calcium-transport behavior of the channel-forming peptide alamethicin is shown to be potential dependent in this system, in contrast to calcium transport by the ionophore Br-A23187, which is unaffected by the potential. The observation of this potential-dependent behavior for alamethicin suggests that this vesicle system may be suitable for direct spectroscopic observation of the voltage-gating process.
Woolley
G A
GA
Deber
C M
CM
D000408:Alamethicin; D000900:Anti-Bacterial Agents; D007473:Ion Channels / Q000502:physiology*; D008081:Liposomes; D008564:Membrane Potentials; D008954:Models, Biological; D010713:Phosphatidylcholines
D000900:Anti-Bacterial Agents; D007473:Ion Channels; D008081:Liposomes; D010713:Phosphatidylcholines; D000408:Alamethicin