Gelsolin is a cytoplasmic, calcium-regulated, actin-modulating protein that binds to the barbed ends of actin filaments, preventing monomer exchange (end-blocking or capping). It can promote nucleation (the assembly of monomers into filaments), as well as sever existing filaments. In addition, this protein binds with high affinity to fibronectin. Plasma gelsolin and cytoplasmic gelsolin are derived from a single gene by alternate initiation sites and differential splicing.Sequence comparisons indicate an evolutionary relationship between gelsolin,villin, fragmin and severin. Six large repeating segments occur in gelsolin and villin, and 3 similar segments in severin and fragmin. While the multiple repeats have yet to be related to any known function of the actin-severing proteins, the superfamily appears to have evolved from an ancestral sequence of 120 to 130 amino acid residues.This gelsolin-like domain can also be found in the C-terminal of the members of Sec23/Sec24 family. They are components of the coat protein complex II (COPII) which promotes the formation of transport vesicles from the endoplasmic reticulum (ER). The Gelsolin structure has a three layers (alpha/beta/alpha) fold and a mixed beta-sheet topology.