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Adseverin is a member of the calcium-regulated gelsolin superfamily of actin-binding proteins. Here we report the crystal structure of the calcium-free N-terminal half of adseverin (iA1-A3) and the Ca(2+)-bound structure of A3, which reveal structural similarities and differences with gelsolin. Solution small-angle X-ray scattering combined with ensemble optimization revealed a dynamic Ca(2+)-dependent equilibrium between inactive, intermediate and active conformations. Increasing calcium concentrations progressively shift this equilibrium from a main population of inactive conformation to the active form. Molecular dynamics simulations of iA1-A3 provided insights into Ca(2+)-induced destabilization, implicating a critical role for the A2 type II calcium-binding site and the A2A3 linker in the activation process. Finally, mutations that disrupt the A1/A3 interface increase Ca(2+)-independent F-actin severing by A1-A3, albeit at a lower efficiency than observed for gelsolin domains G1-G3. Together, these data address the calcium dependency of A1-A3 activity in relation to the calcium-independent activity of G1-G3.

Original publication

DOI

10.1038/ncomms9254

Type

Journal article

Journal

Nat Commun

Publication Date

14/09/2015

Volume

6

Keywords

Actins, Binding Sites, Calcium, Crystallization, Escherichia coli, Gelsolin, Intracellular Calcium-Sensing Proteins, Microfilament Proteins, Molecular Dynamics Simulation, Mutagenesis, Site-Directed, Protein Structure, Tertiary, Scattering, Small Angle, X-Ray Diffraction