Ordered stacking of F-actin layers and mixed lipid bilayers: a columnar liquid crystal.

ABSTRACT

In this Letter, we show how the grooved helical structure of actin microfilaments (F-actin) interacting with mixed fluid lipid bilayers leads to handedness-independent 1D lipid bilayer undulations coupled to longitudinal in-plane ordering of the microfilaments. This longitudinal ordering is forced by the emerging in-plane compression and curvature energy terms of the straight 1D bilayer undulation wave fronts. Thereby, adjacent helices are set into registry along their long axis in their monolayer and π shifted between adjacent monolayers. An ordered composite multilamellar structure emerges by alternate stacking of these lipid bilayers and monolayers of F-actin. This two-dimensionally ordered system has the symmetries of a centered rectangular columnar liquid crystal, the straight 1D wave fronts playing the role of the classical molecular columns.