Binding of curvature-inducing proteins onto tethered vesicles

TL;DR

This study combines theoretical and simulation approaches to understand how curvature-inducing proteins bind to tethered vesicles, revealing their sensing mechanisms, phase transitions, and resulting membrane morphologies.

Contribution

It introduces a mean-field theory and meshless membrane simulation to analyze protein binding and curvature sensing on tethered vesicles, highlighting phase behavior and morphological features.

Findings

Force-dependence curves are symmetric and reflect curvature sensing.

Bending rigidity and spontaneous curvature can be estimated from curves.

First-order phase transitions occur between low and high protein densities.

Abstract

A tethered vesicle, which consists of a cylindrical membrane tube and a spherical vesicle, is produced by a mechanical force that is experimentally imposed by optical tweezers and a micropipette. This tethered vesicle is employed for examining the curvature sensing of curvature-inducing proteins. In this study, we clarify how the binding of proteins with a laterally isotropic spontaneous curvature senses and generates the membrane curvatures of the tethered vesicle using mean-field theory and meshless membrane simulation. The force-dependence curves of the protein density in the membrane tube and the tube curvature are reflection symmetric and point symmetric, respectively, from the force point, in which the tube has a sensing curvature. The bending rigidity and spontaneous curvature of the bound proteins can be estimated from these force-dependence curves. First-order transitions can occur between low and high protein densities in the tube at both low and high force amplitudes. The simulation results of the homogeneous phases agree very well with the theoretical predictions. In addition, beaded-necklace-like tubes with microphase separation are found in the simulation.