%0 Journal Article %J Biophysical Journal %D 2008 %T Dynamic viscoelasticity of actin cross-linked with wild-type and disease-causing mutant alpha-actinin-4 %A Ward, Sabine M. Volkmer %A Weins, Astrid %A Pollak, Martin R. %A Weitz, David A %X The actin cross-linker alpha-actinin-4 has been found to be indispensable for the structural and functional integrity of podocytes; deficiency or alteration of this protein due to mutations results in kidney disease. To gain insight into the effect of the cross-linker on cytoskeletal mechanics, we studied the macroscopic rheological properties of actin networks cross-linked with wild-type and mutant alpha-actinin-4. The frequency-dependent viscoelasticity of the networks is characterized by an elastic plateau at intermediate frequencies, and relaxation toward fluid properties at low frequencies. The relaxation frequencies of networks with mutant alpha-actinin-4 are an order of magnitude lower than that with the wild-type, suggesting a slower reaction rate for the dissociation of actin and alpha-actinin for the mutant, consistent with a smaller observed equilibrium dissociation constant. This difference can be attributed to an additional binding site that is exposed as a result of the mutation, and can be interpreted as a difference in binding energy barriers. This is further supported by the Arrhenius-like temperature dependence of the relaxation frequencies. %B Biophysical Journal %V 95 %P 4915-4923 %G eng %U https://www.cell.com/biophysj/fulltext/S0006-3495(08)78630-2 %N 10