Two- or three-step assembly of banana-shaped proteins coupled with shape transformation of lipid membranes

TL;DR

This study uses meshless membrane simulations to explore how banana-shaped proteins induce local membrane bending and assemble in multiple steps, leading to significant shape transformations of vesicles and tubes.

Contribution

It reveals a novel two- or three-step assembly process of banana-shaped proteins and their role in membrane shape changes, which was not previously understood.

Findings

Proteins assemble via two continuous directional phase separations.

Increased rod curvature causes assembly along azimuthal and longitudinal directions.

High curvature induces tubular scaffold formation in vesicles.

Abstract

BAR superfamily proteins have a banana-shaped domain that causes the local bending of lipid membranes. We study as to how such a local anisotropic curvature induces effective interaction between proteins and changes the global shape of vesicles and membrane tubes using meshless membrane simulations. The proteins are modeled as banana-shaped rods strongly adhered to the membrane. Our study reveals that the rods assemble via two continuous directional phase separations unlike a conventional two-dimensional phase separation. As the rod curvature increases, in the membrane tube the rods assemble along the azimuthal direction and subsequently along the longitudinal direction accompanied by shape transformation of the tube. In the vesicle, in the addition to these two assembly processes, further increase in the rod curvature induces tubular scaffold formation.