The structure of the C-terminal actin-binding domain of talin

Abstract

Talin is a large dimeric protein that couples integrins to cytoskeletal actin. Here, we report the structure of the C-terminal actin-binding domain of talin, the core of which is a five-helix bundle linked to a C-terminal helix responsible for dimerisation. The NMR structure of the bundle reveals a conserved surface-exposed hydrophobic patch surrounded by positively charged groups. We have mapped the actin-binding site to this surface and shown that helix 1 on the opposite side of the bundle negatively regulates actin binding. The crystal structure of the dimerisation helix reveals an antiparallel coiled-coil with conserved residues clustered on the solvent-exposed face. Mutagenesis shows that dimerisation is essential for filamentous actin (F-actin) binding and indicates that the dimerisation helix itself contributes to binding. We have used these structures together with small angle X-ray scattering to derive a model of the entire domain. Electron microscopy provides direct evidence for binding of the dimer to F-actin and indicates that it binds to three monomers along the long-pitch helix of the actin filament.

The tale of two talins – two isoforms to fine‐tune integrin signalling

“…Full‐length talin is dimeric, and helix 62 [dimerisation domain (DD)] forms an antiparallel dimer with another talin molecule 74. In all our experiments to date, we see talin as a constitutive dimer when the DD is present; however, a calpain cleavage site immediately prior to the DD means it can be cleaved to yield monomeric talin 71.…”

“…The current model of talin function envisages the C‐terminal ABS3 74 as responsible for the initial force exerted on talin that leads to unfolding of the mechanosensitive talin rod domain, R3. This triggers vinculin interactions and leads to adhesion maturation 23.…”

Subcellular Localization of Talin Is Regulated by Inter-domain Interactions

“…Therefore, our results imply that the presence of Domain E prevents interaction of talin with cytoskeletal actin, although the precise mechanism remains to be resolved. Several regions of talin, including the talin FERM domain and several noncontiguous regions in the rod domain, bind actin (53,58,59), and it is reasonable to propose that one or more of these sites may be cryptic in FL talin and masked by the Domain E-F3 interaction.…”

Structural model and functional significance of pH-dependent talin–actin binding for focal adhesion remodeling

“…Initial 1 H N , 15 N, 13 C␣, 13 C␤, and 13 CЈ backbone resonance assignments of a shorter talin USH-I/LWEQ construct lacking the dimerization helix (2300 -2482) were made at 318 K and pH 6.0 using standard 3D tripleresonance experiments (18). Resonance assignments obtained at 318 K were transferred to spectra of a longer talin USH-I/LWEQ construct (2300 -2501) at 305 K using standard 3D triple-resonance experiments (40).…”

“…The simulations were originally carried out by using a homology model based on the structure of Hip1R (Hip-1-related). During the course of this study, Critchley and coworkers determined an NMR structure of the talin I/LWEQ domain (18) including the USH segment, but excluding the COOH-terminal dimerization domain (Protein Data Bank ID code 2JSW). Simulations using this NMR structure led to conclusions very similar those of the homology model, and those results are shown here.…”