Binding of thermalized and active membrane curvature-inducing proteins

TL;DR

This study explores how membrane-bound proteins induce phase changes in membranes, revealing equilibrium and nonequilibrium behaviors, phase transitions, and the effects of activity on membrane morphology through analytical and numerical methods.

Contribution

It combines analytical and numerical approaches to characterize membrane phase behavior induced by curvature proteins, including active processes, revealing new phase transition insights.

Findings

Membrane exhibits three phases: unbound, bound, and separated/corrugated.

Transitions between phases include second order and first order, with some becoming continuous.

Active binding/unbinding alters the stability of the separated/corrugated phase.

Abstract

Membrane phase behavior induced by the binding of curvature-inducing proteins is studied by a combination of analytical and numerical approaches. In thermal equilibrium under the detailed balance between binding and unbinding, the membrane exhibits three phases: an unbound uniform flat phase (U), a bound uniform flat phase (B), and a separated/corrugated phase (SC). In the SC phase, the bound proteins form hexagonally-ordered bowl-shaped domains. The transitions between the U and SC phases and between the B and SC phases are second order and first order, respectively. At a small spontaneous curvature of the protein or high surface tension, the transition between B and SC phases becomes continuous. Moreover, a first-order transition between the U and B phases is found at zero spontaneous curvature driven by the Casimir-like interactions between rigid proteins. Furthermore, nonequilibrium dynamics is investigated by the addition of active binding and unbinding at a constant rate. The active binding and unbinding processes alter the stability of the SC phase.