Calcium-regulated, actin-modulating protein that binds to the plus (or barbed) ends of actin monomers or filaments, preventing monomer exchange (end-blocking or capping). It can promote the assembly of monomers into filaments (nucleation) as well as sever filaments already formed. Plays a role in ciliogenesis (By similarity). Binds to actin and to fibronectin. Identified in a complex composed of ACTA1, COBL, GSN AND TMSB4X (By similarity). Interacts with the inactive form of EIF2AK2/PKR (By similarity). A cytoplasmic form may also exist. Phosphorylated on tyrosine residues in vitro. Belongs to the villin/gelsolin family.