Depolymerizes growing actin filaments in muscle cells; required for the assembly of actin filaments into the functional contractile myofilament lattice of muscle (PubMed:8107682). Competes with unc-87 for actin binding and inhibits the actin-bundling activity of unc-87 (PubMed:17684058). Interacts with F-actin. Isoforms only share an exon that codes for the initiator Met. Belongs to the actin-binding proteins ADF family.