Ionophoric Activity of Truncated Gramicidin A Analogue in Phospholipid Bilayers and Mitochondrial and Erythrocyte Membranes

摘要

Ionophoric activities of an N-terminus truncated gramicidin A (gA) analogue (mini-gramicidin) andits covalent dimer were studied in planar bilayer phospholipid membranes (BLM) using macroscopic currentmeasurements (at high concentrations of the peptides) and single-channel recordings. As with gA-induced cur-rents, mini-gramicidin-stimulated macroscopic currents through BLM underwent sensitized photoinactivation,i.e. were suppressed after irradiation with visible light in the presence of a photosensitizer generating singletoxygen. The sensitivity of the tested compounds to photoinactivation descended in the following order: mini-gramicidin dimer > mini-gramicidin monomer > gA. The data from single-channel measurements and kineticanalysis of flash-induced photoinactivation obtained at different levels of macroscopic currents suggest thatmini-gramicidin and its covalent dimer induce a variety of conducting states; their ratio depends on membranethickness. Analysis of natural (mitochondrial and erythrocyte) membranes established that ionophoric activitiesof mini-gramicidin and its covalent dimer depend essentially on the membrane type.