Protein-membrane interactions with a twist

Within a framework of elasticity theory and geometry, the Twister mechanism has been proposed some years ago for describing the interaction between a biofilament containing a twisted hydrophobic strip and a lipid membrane: this mechanism can induce membrane deformations possibly conducting to its opening. The present work intends to extend this model to the case of the interactions between a membrane and protein regions conserving their folds using coarse-grained molecular dynamics simulations. The protein region is modeled as a cylinder stabilized by a tensegrity scheme, leading to an elasticity similar to that observed in real proteins. Recording molecular dynamics trajectories of this cylinder in the presence of a fluid lipid bilayer membrane permits to investigate the effect of the positions of the hydrophobic parts on the interaction with the membrane. The entire configuration space is explored by systematically varying the strip width, the twisting of the strip as well as the range of hydrophobic interactions between the cylinder and the membrane. Three different states are observed: no interaction between cylinder and membrane, cylinder in contact with the membrane surface and cylinder inserted in the membrane with a variable tilt angle. The variations of the tilt angle are explained using a qualitative model based on the total hydrophobic moment of the cylinder. A deformation pattern of the membrane, previously predicted for the filament-membrane interaction by the Twister model, is observed for the state when the cylinder is in contact with the membrane surface, which allows to estimate the applied torques.