Villin 14T, Actin-Severing Domain

Villin 14T is the amino-terminal domain of the actin-severing and bundling protein, villin. Villin is a member of a protein family which regulates eukaryotic, cytoskeletal actin by severing, capping, and nucleating actin filaments. Actin-severing proteins consist of three or six homologous, repetetive domains of about 130 amino acid residues in length, such as 14T. Villin is thought to have two calcium (Ca2+)-binding sites. The reason for this is that actin-binding is dependent upon calcium and is interrupted by the presence of phosphatidyl inositol 4,5-bisphosphate (PIP2).
The 126 amino acid residue villin 14T domain binds both calcium and actin monomers. It is a conserved domain among the actin-severing proteins. It consists of a central beta-sheet of 4 antiparallel strands. A fifth parallel strand is found at one edge of the protein. Three right-handed alpha helices shown in blue add to the secondary structure of this domain, as well as two 310 alpha helices shown in lavender.

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