ИСТИНА

Gramicidin A (gA) is a well-known peptide forming ion-conducting channels in a lipid membrane by transbilayer dimerization. gA channel is characterized by conductance, dimerization probability and channel lifetime. The channel characteristics depend on elastic properties of the lipid bilayer (thickness, spontaneous curvature and etc.). We studied how gA dimer is formed from two initially isolated monomers in the framework of theory of elasticity of liquid crystals adopted to lipid membranes. Because gA monomer is shorter than the lipid monolayer thickness, gA deforms lipid bilayer in its vicinity. If two monomers are close enough, their induced deformations overlap and monomers interact with each other. We calculated the interaction energy of monomers at different distances, obtained channel lifetime and probability of dimer formation. The results were compared with the experimental data [1, 2]. The features of monomer interaction could explain the long persistence of gA channels in planar bilayer after fusion with gA-containing liposomes [3] without assumptions of internal gating. Monomer interactions predict gA clustering at surface concentration of Ccrit = 0.05 nm–2, which is in good agreement with the experimental data [4]. 1. Goulian, M., et al. "Gramicidin channel kinetics under tension." Biophysical Journal 74.1 (1998): 328-337. 2. Lundbæk, Jens A., and Olaf S. Andersen. "Spring constants for channel-induced lipid bilayer deformations estimates using gramicidin channels." Biophysical journal 76.2 (1999): 889-895. 3. Jones, Tyson L., et al. "Gramicidin channels are internally gated." Biophysical journal 98.8 (2010): 1486-1493. 4. Diociaiuti, Marco, et al. "Aggregation of gramicidin A in phospholipid Langmuir–Blodgett monolayers." Biophysical journal82.6 (2002): 3198-3206.