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Introducing a charged group near the N-terminus of gramicidin A (gA) is supposed to suppress its ability to form ion channels by restricting its head-to-head dimerisation. However, des-formyl-gramicidin was earlier found to exhibit significant protonophoric activity both in artificial and mitochondrial membranes. The present study deals with the activity of [Lys1]gA, [Lys3]gA, [Glu1]gA and [Glu3]gA in model membrane systems (planar lipid bilayers and liposomes) and mitochondria. All of the peptides induced proton conductivity in liposomes with almost the same potency, however, cationic derivatives were also able to cause non-specific leakage from liposomes. Measurements of electrical current through a planar lipid membrane at 100 mM HCl showed the formation of gA-like ion channels. However, effective concentrations of cationic peptides were by two orders of magnitude higher than those of anionic peptides. [Glu1]gA displayed considerably more pronounced effect on mitochondrial membrane potential compared to other peptides. A study of the properties of hybrid channels composed of cationic and anionic peptides is in progress.