Sunday, 20 August, 2006
Actin-Binding Proteins Sensitively Mediate F-Actin Bundle Stiffness
Mireille M. A. E. Claessens, Mark Bathe, Erwin Frey, Andreas R. Bausch -
Nature Materials 5, 748 (2006)
Despite the importance of F-actin bundle mechanical properties to many cytoskeletal processes, quantitative investigations of their mediation by actin binding proteins (ABPs) remain scarce. We directly measure the bending stiffness of F-actin crosslinked by three ABPs that are ubiquitous in eukaryotes and observe distinct regimes of bundle bending stiffness that differ by orders of magnitude depending on ABP type, concentration, and bundle size. The reported behaviour is reproduced quantitatively by a molecular-based mechanical model in which ABP shearing competes with F-actin extension/compression. A generic scaling parameter identifying the relevant bundle bending stiffness regimes is presented. Our results shed new light on the potential role of ABPs in associated cellular processes and demonstrate how single molecule properties determine mesoscopic material properties. Moreover, the observed mechanics of fiber bundle bending are completely general, with broad implications not only for cytoskeletal mechanics but also for the rational design of functional materials.