title: Calcium-controlled conformational choreography in the N-terminal half of adseverin.
abstract: 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.
authors.affiliation: Division of Structural Biology, University of Oxford, Henry Wellcome Building for Genomic Medicine, Oxford OX3 7BN, UK.|Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Biopolis, Singapore 138673, Singapore.|School of Biochemistry, Institute of Science, Suranaree University of Technology, 111 University Avenue, Muang, Nakhon Ratchasima 30000, Thailand.
authors.forename: Sakesit
authors.initials: S
authors.lastname: Chumnarnsilpa
authors.affiliation: Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Biopolis, Singapore 138673, Singapore.|Department of Biochemistry, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Robinson
authors.affiliation: Division of Structural Biology, University of Oxford, Henry Wellcome Building for Genomic Medicine, Oxford OX3 7BN, UK.|Science Division, Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Grimes
authors.affiliation: Division of Structural Biology, University of Oxford, Henry Wellcome Building for Genomic Medicine, Oxford OX3 7BN, UK.
authors.forename: Cedric
authors.initials: C
authors.lastname: Leyrat
mesh_terms: D000199:Actins / Q000378:metabolism*; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D003460:Crystallization; D004926:Escherichia coli; D018260:Gelsolin / Q000737:chemistry / Q000378:metabolism*; D052139:Intracellular Calcium-Sensing Proteins / Q000737:chemistry / Q000378:metabolism; D008840:Microfilament Proteins; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D000199:Actins; D018260:Gelsolin; D052139:Intracellular Calcium-Sensing Proteins; D008840:Microfilament Proteins; C065395:scinderin; D002118:Calcium