Controls reversibly actin polymerization and depolymerization in a pH-sensitive manner. It has the ability to bind G- and F-actin in a 1:1 ratio of cofilin to actin. It is the major component of intranuclear and cytoplasmic actin rods. Carlier, M. et al. (1999) J. Biol. Chem. 274, 33827-33830. Arber, S. et al. (1998) Nature 393, 805-809. Yang, N. et al. (1998) Nature 393, 809-812.