title: New insights into the role of the disordered WIP N-terminal domain revealed by NMR structural characterization.
abstract: WASp-interacting protein (WIP) is an intrinsically disordered 503-residue polypeptide with a key role in actin polymerization in activated T cells. Its interaction with actin is mediated by a pair of conserved actin binding motifs (ABMs) at the WIP N-terminus, a domain that has not been investigated in its unbound form. Here we use NMR to investigate the biophysical behavior of the N-terminal ABM in WIP using protonless (13)C'-detected spectroscopy. Secondary chemical shifts, residual dipolar couplings and temperature effects identify residual structure throughout the ABM, which exhibits transient helical and β-strand character for residues 30-42 and 44-62, respectively. These observed structural propensities echo the structure observed in the actin-bound state of the ABM. Furthermore, residues preceding the canonical ABM (17-25) and conserved among WIP-related proteins exhibit transient β-strand character, suggesting that the WIP(N) interaction epitope extends towards the N-terminal polyproline motif. This suggests a possible role for this region in mediating the WIP interaction with polyproline binders such as profilin. In revealing these features of the WIP ABM this study demonstrates the unique ability of NMR in characterizing unstructured domains and provides necessary information for further investigation of WIP-mediated protein-protein interactions.
authors.affiliation: Department of Chemistry, Bar Ilan University, Ramat Gan, Israel.
authors.forename: Hila
authors.initials: H
authors.lastname: Elazari-Shalom
authors.forename: Hadassa
authors.initials: H
authors.lastname: Shaked
authors.forename: Santiago
authors.initials: S
authors.lastname: Esteban-Martin
authors.forename: Xavier
authors.initials: X
authors.lastname: Salvatella
authors.forename: Mira
authors.initials: M
authors.lastname: Barda-Saad
authors.forename: Jordan H
authors.initials: JH
authors.lastname: Chill
mesh_terms: D002942:Circular Dichroism; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D051316:Wiskott-Aldrich Syndrome Protein / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D047908:Intracellular Signaling Peptides and Proteins; C109903:WIPF1 protein, human; D051316:Wiskott-Aldrich Syndrome Protein
keywords: 13C-detected spectroscopy; NMR; Wiskott-Aldrich syndrome; actin binding motif; intrinsically disordered proteins; structural biology