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 (Tm) and only in the presence of the protein. No similar interdigitation of the membrane lipids was observed temperatures well above Tm 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 Tm 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 Tm 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.