InterPro domain: IPR007122

Gelsolin is an actin-modulating protein that severs F-actin, caps the barbed ends of actin filaments preventing monomer exchange, and promotes the nucleation step of actin polymerisation [ 1 , 2 ]. It can be regulated by Ca2+ and phosphoinositides [ 3 ]. The interaction between gelsolin and tropomyosin modulates actin dynamics [ 4 ]. Gelsolin also plays a role in ciliogenesis [ 5 ]. The structure of gelsolin has been solved [ 6 ].

Villin is an actin-binding protein that is found in a variety of tissues. It is able to bind to the barbed end of actin filaments with high affinity and can sever filaments [ 7 ]. In addition, villin's activity is important for actin bundling in certain cell types [ 8 ]. It was first isolated as a major component of the core of intestinal microvilli [ 9 ].

Villin/gelsolin family includes other actin-binding proteins such as severin and supervillin [ 10 ]. 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 [ 11 ].

1. The gelsolin family of actin regulatory proteins: modular structures, versatile functions. FEBS Lett. 552, 75-81
2. Preparation and characterization of pig plasma and platelet gelsolins. Eur. J. Biochem. 161, 69-76
3. Modulation of gelsolin function by phosphatidylinositol 4,5-bisphosphate. Nature 325, 362-4
4. The interaction of gelsolin with tropomyosin modulates actin dynamics. FEBS J. 280, 4600-11
5. Functional genomic screen for modulators of ciliogenesis and cilium length. Nature 464, 1048-51
6. The crystal structure of plasma gelsolin: implications for actin severing, capping, and nucleation. Cell 90, 661-70
7. Different calcium dependence of the capping and cutting activities of villin. J. Biol. Chem. 261, 9274-81
8. From the structure to the function of villin, an actin-binding protein of the brush border. Bioessays 12, 403-8
9. Villin: the major microfilament-associated protein of the intestinal microvillus. Proc. Natl. Acad. Sci. U.S.A. 76, 2321-5
10. Gelsolin superfamily proteins: key regulators of cellular functions. Cell. Mol. Life Sci. 61, 2614-23
11. Nucleotide sequence of pig plasma gelsolin. Comparison of protein sequence with human gelsolin and other actin-severing proteins shows strong homologies and evidence for large internal repeats. J. Mol. Biol. 203, 1127-33