Correction

Abstract

2012. A Mechanochemical Model of Actin Filaments. Yogurtcu ON, Kim JS, Sun SX. Biophys J. 103(4): 719–727. Due to an incorrect interpretation of the experimental stretching stiffness values of F-actin, the model parameters shown in the original text are incorrect. The parameters are now adjusted to correctly describe the stretching mechanical properties of actin filaments. Table 1 below shows the model parameters, where the updated values are shown in bold. Significant changes to the results are discussed below. The overall conclusions are unchanged by the new parameters.Table 1Corrected bond stiffness parameters, bond free energies and intrinsic geometric parameters for our modelATP–ATPADP–ADPkl [pN/μm]4.8 × 1064.29 × 106kθ [pN·μm]0.270.12kφ [pN·μm]0.330.17kd [pN/μm]9.99 × 1039.71 × 103kφ [pN·μm]5.45.1kψ [pN·μm]1.20.5ΔGlong [kBT ]−20.07−18.07ΔGdiag [kBT ]−8.08−6.08l0 [nm]6.006.00θ [◦]28.5528.55φ [◦]−6.43−6.43d0 [nm]6.006.00φ0 [◦]104.27104.27ψ0 [◦]60.0060.0 Open table in a new tab The filament with the new parameter set is an order of magnitude stiffer against axial stresses and thus correctly represents the experimental results of Ref. 32 (Kojima et al., PNAS, 91, 12962-12966, 1994). Bending persistence lengths of F- ATP and F-ADP models are relatively unchanged, but under higher bending forces chemical state changes are more pronounced with respect to the original model. With the new parameters, the model filament on average shows about 50% less out of plane deflection. Also, stretch-induced filament tip twist relation parameter is about three times smaller with respect to the original report. In addition, cofilin binding cooperativity is on average about 50% weaker and the cooperativity is localized and is only up to the i + 4th neighboring monomers. The effect of the new parameters on the mechanochemical treatment of F-actin is shown below (Figure 6) . Since the stretching strains are now ten times smaller with respect to the original model, the monomers preferentially stay in the ATP state (Figure 6A). In comparison to the original model, bending deflections are enhanced, especially for higher forces. As a result, ADP-type monomers form a larger cluster at the location where the bond strains are large (Figure 6B and 6C). The authors apologize for this error and thank Edward H. Egelman for bringing this to their attention. A Mechanochemical Model of Actin FilamentsYogurtcu et al.Biophysical JournalAugust 22, 2012In BriefIn eukaryotic cells, actin filaments are involved in important processes such as motility, division, cell shape regulation, contractility, and mechanosensation. Actin filaments are polymerized chains of monomers, which themselves undergo a range of chemical events such as ATP hydrolysis, polymerization, and depolymerization. When forces are applied to F-actin, in addition to filament mechanical deformations, the applied force must also influence chemical events in the filament. We develop an intermediate-scale model of actin filaments that combines actin chemistry with filament-level deformations. Full-Text PDF Open Archive