title: Calcium-dependent conformational stability of modules 1 and 2 of human gelsolin.
abstract: Gelsolin modulates the actin cytoskeleton in the cytoplasm and clears the circulation of stray filaments. In vitro, gelsolin cleaves, nucleates and caps actin filaments, activities that are calcium-dependent. Both cellular and secreted forms share a sequence of 730 residues comprising six homologous modules termed G1-G6. A disulphide bond is formed in secreted G2, whereas in the cytoplasm it remains reduced. A point mutation in G2 causes an amyloidosis with neurological, ophthalmological and dermatological symptoms. This mutation does not affect the cytoplasmic form, while the secreted form is proteolysed. As a first step towards understanding how gelsolin folds and functions in different cellular compartments, we have characterized at equilibrium the urea-induced unfolding of G1 and G2, with or without calcium and/or disulphide bond. G1 and G2 both exhibit two-state unfolding behaviour and are stabilized by calcium. The disulphide bond also contributes to the stability of G2. In the absence of Ca(2+) and disulphide bond, G2 adopts a non-native conformation, suggesting that folding of G2 in the cytoplasm relies on the presence of surrounding modules or other molecular partners.
authors.affiliation: Institut de Biologie Structurale J.-P. Ebel (CEA, CNRS, UJF), Laboratoire d'Ingénierie des Macromolécules, 41 rue Jules Horowitz, 38027 Grenoble, France. andre.zapun@ibs.fr
authors.forename: A
authors.initials: A
authors.lastname: Zapun
authors.forename: S
authors.initials: S
authors.lastname: Grammatyka
authors.forename: G
authors.initials: G
authors.lastname: Déral
authors.forename: T
authors.initials: T
authors.lastname: Vernet
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002850:Chromatography, Gel; D018260:Gelsolin / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D018260:Gelsolin; D011994:Recombinant Proteins; D002118:Calcium