ИСТИНА

Gramicidin A (gA) is a well-known pentadecapeptide that forms ion channels — conductive dimers — through transbilayer dimerization of gA monomers. It has been previously demonstrated that the lifetime of tandem gA channels, i.e. couples of gA dimers, constructed from pairs of linked gA monomers in each lipid monolayer, is about 1000 times greater than the lifetime of a single gA dimer. Besides, for gA analogs with N-terminal valine replaced by glycine or tyrosine, the time of relaxation to equilibrium increased, but not decreased, upon elevation of the total membrane conductance, thus contradicting the classical kinetic theory. In the framework of the elastic theory of liquid crystals adapted to lipid bilayers, we calculated lipid membrane deformations near gA monomers and dimers. If gA monomers/dimers are close enough, the deformations produced by them overlap, thereby leading to membrane-mediated interactions between gA molecules. According to our present results, the lifetime of tandem gA channels and dimerization constant calculated with the help of Mayer cluster expansion, using gA interaction energies, depend on gA concentration. We also demonstrated that these effects may be modulated by incorporation of other peptides (“impurities”) into the lipid membrane.