title: Domain-domain interactions in filamin A (16-23) impose a hierarchy of unfolding forces.
abstract: The quaternary structure of Filamin A (FLNa) 16-23 was recently shown to exhibit multiple domain-domain interactions that lead to a propeller-like construction. Here we present single-molecule force spectroscopy experiments to show a wide variety of mechanical responses of this molecule and compare it with its linear counterpart FLNa 1-8. The compact structure of FLNa 16-23 leads to a broad distribution of rupture forces and end-to-end lengths in the force-extension mode and multiple unraveling timescales in the force-clamp mode. Moreover, a subset of force-extension trajectories reveals a mechanical hierarchy in which the rupture of domain-domain interactions at high forces (>200 pN) liberates the unfolding of individual domains at low forces (∼100 pN). This mechanism may also explain the order-of-magnitude difference in the rates of the biexponential fits to the distribution of unfolding dwell times under force-clamp. Overall, FLNa 16-23 under a force of 100 pN is more compliant than the linear FLNa 1-8. Because a physiological role of FLNa is to crosslink actin filaments, this range of responses allows it to accommodate a broad spectrum of forces exerted by the cell and its environment.
authors.affiliation: Department of Physics and Center for Soft Matter Research, New York University, New York, New York, USA.
authors.forename: Tianyou
authors.initials: T
authors.lastname: Xu
authors.forename: Herbert
authors.initials: H
authors.lastname: Lannon
authors.forename: Sébastein
authors.initials: S
authors.lastname: Wolf
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Nakamura
authors.forename: Jasna
authors.initials: J
authors.lastname: Brujic
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000818:Animals; D064448:Filamins / Q000737:chemistry* / Q000378:metabolism; D018625:Microscopy, Atomic Force; D009842:Oligopeptides / Q000737:chemistry; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D058767:Protein Unfolding; D061987:Sf9 Cells; D018411:Spodoptera
chemical_list: D000199:Actins; D064448:Filamins; D009842:Oligopeptides