Interdigitation of Lipids Induced by Membrane-Active Proteins

The membrane-active protein Nogo-66 is found to induce interdigitation in dimyristoylphosphocholine membranes. Extensive molecular dynamics simulations have been employed to probe the interactions of Nogo-66 with these model membranes. This phase change happens when the temperature is close to the main transition temperature of the membrane (T_m) and only in the presence of the protein. No similar interdigitation of the membrane lipids was observed temperatures well above T_m in the presence of the protein. In addition, in protein-free simulations, no interdigitation of the membrane lipids was found both at temperatures near or well above T_m indicating that the observed effect is caused by the interactions of Nogo-66 with the membrane. Analysis of the simulations suggest protein-membrane interactions, even if transient, alter the lifetimes of lipid head defects and can potentially alter the effective T_m and cause interdigitation. This study emphasize the importance of membrane-active proteins and their interactions with membranes leading to phase transitions which would affect other membrane-related processes such as domain formation.