Shape deformation of lipid membranes by banana-shaped protein rods: Comparison with isotropic inclusions and membrane rupture

TL;DR

This study uses simulations to analyze how banana-shaped protein rods deform lipid membranes, comparing their effects with isotropic inclusions and exploring conditions leading to membrane rupture and vesicle division.

Contribution

It provides new insights into the deformation mechanisms of lipid membranes induced by anisotropic protein rods versus isotropic inclusions, highlighting factors influencing membrane rupture and inversion.

Findings

Rod assembly causes membrane deformation and rupture under certain conditions.

Isotropic inclusions with similar rigidity distribute uniformly, unlike stiff inclusions that induce shape changes.

High rod density and stiffness can lead to vesicle rupture and formation of high-genus vesicles.

Abstract

The assembly of curved protein rods on fluid membranes is studied using implicit-solvent meshless membrane simulations. As the rod curvature increases, the rods on a membrane tube assemble along the azimuthal direction first and subsequently along the longitudinal direction. Here, we show that both transition curvatures decrease with increasing rod stiffness. For comparison, curvature-inducing isotropic inclusions are also simulated. When the isotropic inclusions have the same bending rigidity as the other membrane regions, the inclusions are uniformly distributed on the membrane tubes and vesicles even for large spontaneous curvature of the inclusions. However, the isotropic inclusions with much larger bending rigidity induce shape deformation and are concentrated on the region of a preferred curvature. For high rod density, high rod stiffness, and/or low line tension of the membrane edge, the rod assembly induces vesicle rupture, resulting in the formation of a high-genus vesicle. A gradual change in the curvature suppresses this rupture. Hence, large stress, compared to the edge tension, induced by the rod assembly is the key factor determining rupture. For rod curvature with the opposite sign to the vesicle curvature, membrane rupture induces inversion of the membrane, leading to division into multiple vesicles as well as formation of a high-genus vesicle.