title: Cofilin increases the bending flexibility of actin filaments: implications for severing and cell mechanics.
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 microm, corresponding to a flexural rigidity of 0.040 pN microm(2). Cofilin binding lowers the persistence length approximately 5-fold to a value of 2.2 microm and the filament flexural rigidity to 0.0091 pN microm(2). 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.
authors.affiliation: Yale University, Department of Molecular Biophysics and Biochemistry, 260 Whitney Avenue, New Haven, CT 06520, USA.
authors.forename: Brannon R
authors.initials: BR
authors.lastname: McCullough
authors.forename: Laurent
authors.initials: L
authors.lastname: Blanchoin
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Martiel
authors.forename: Enrique M
authors.initials: EM
authors.lastname: De la Cruz
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D051340:Cofilin 2 / Q000502:physiology*; D003198:Computer Simulation; D003599:Cytoskeleton / Q000502:physiology*; D008840:Microfilament Proteins / Q000502:physiology*; D018583:Pliability; D011817:Rabbits
chemical_list: D051340:Cofilin 2; D008840:Microfilament Proteins