Cofilin increases the bending flexibility of actin filaments: implications for severing and cell mechanics |
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Authors: | McCullough Brannon R Blanchoin Laurent Martiel Jean-Louis De la Cruz Enrique M |
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Institution: | 1 Yale University, Department of Molecular Biophysics and Biochemistry, 260 Whitney Avenue, New Haven, CT 06520, USA 2 Institut de Recherches en Technologie et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique and Université Joseph Fourier, F38054 Grenoble, France 3 Université Joseph Fourier, TIMC-IMAG Laboratory, Grenoble, France; CNRS UMR 5525, Grenoble, France; INSERM, IRF 130, Grenoble, France |
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Abstract: | We determined the flexural (bending) rigidities of actin and cofilactin filaments from a cosine correlation function analysis of their thermally driven, two-dimensional fluctuations in shape. The persistence length of actin filaments is 9.8 μm, corresponding to a flexural rigidity of 0.040 pN μm2. Cofilin binding lowers the persistence length ∼5-fold to a value of 2.2 μm and the filament flexural rigidity to 0.0091 pN μm2. That cofilin-decorated filaments are more flexible than native filaments despite an increased mass indicates that cofilin binding weakens and redistributes stabilizing subunit interactions of filaments. We favor a mechanism in which the increased flexibility of cofilin-decorated filaments results from the linked dissociation of filament-stabilizing ions and reorganization of actin subdomain 2 and as a consequence promotes severing due to a mechanical asymmetry. Knowledge of the effects of cofilin on actin filament bending mechanics, together with our previous analysis of torsional stiffness, provide a quantitative measure of the mechanical changes in actin filaments associated with cofilin binding, and suggest that the overall mechanical and force-producing properties of cells can be modulated by cofilin activity. |
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Keywords: | single molecule imaging biopolymer mechanics persistence length severing |
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