Eur. Phys. J. E (2015) 38: 50
https://doi.org/10.1140/epje/i2015-15050-3

Regular Article

A single charge in the actin binding domain of fascin can independently tune the linear and non-linear response of an actin bundle network

¹ Lehrstuhl für Zellbiophysik E27, Physik-Department, Technische Universität München, Garching, Germany
² Institute for Computational Mechanics, Department of Mechanical Engineering, Technische Universität München, Garching, Germany
³ Institute for Theoretical Physics, Universität Göttingen, Göttingen, Germany
⁴ Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
⁵ Institute of Medical Engineering IMETUM and Department of Mechanical Engineering, Technische Universität München, Garching, Germany

^* e-mail: oliver.lieleg@tum.de

Received: 23 January 2015
Revised: 12 March 2015
Accepted: 2 April 2015
Published online: 27 May 2015

Abstract

Actin binding proteins (ABPs) not only set the structure of actin filament assemblies but also mediate the frequency-dependent viscoelastic moduli of cross-linked and bundled actin networks. Point mutations in the actin binding domain of those ABPs can tune the association and dissociation dynamics of the actin/ABP bond and thus modulate the network mechanics both in the linear and non-linear response regime. We here demonstrate how the exchange of a single charged amino acid in the actin binding domain of the ABP fascin triggers such a modulation of the network rheology. Whereas the overall structure of the bundle networks is conserved, the transition point from strain-hardening to strain-weakening sensitively depends on the cross-linker off-rate and the applied shear rate. Our experimental results are consistent both with numerical simulations of a cross-linked bundle network and a theoretical description of the bundle network mechanics which is based on non-affine bending deformations and force-dependent cross-link dynamics.