Pressure-Dependent Chemical Shifts in the R3 Domain of Talin Show that It Is Thermodynamically Poised for Binding to Either Vinculin or RIAM

• Published in: Structure (London) Vol. 25; no. 12; pp. 1856 - 1866.e2
• Main Authors: Baxter, Nicola J., Zacharchenko, Thomas, Barsukov, Igor L., Williamson, Mike P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 05.12.2017
• Subjects: Adaptor Proteins, Signal Transducing - chemistry; Adaptor Proteins, Signal Transducing - metabolism; Animals; Binding Sites; cell adhesion; chemical shift; focal adhesion complex; Hydrostatic Pressure; Membrane Proteins - chemistry; Membrane Proteins - metabolism; Mice; Molecular Docking Simulation; Molecular Dynamics Simulation; Protein Binding; singular value decomposition; talin; Talin - chemistry; Talin - metabolism; vinculin; Vinculin - chemistry; Vinculin - metabolism; vinculin; talin; focal adhesion complex; cell adhesion; hydrostatic pressure; chemical shift; singular value decomposition
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2017.10.008

Talin mediates attachment of the cell to the extracellular matrix. It is targeted by the Rap1 effector RIAM to focal adhesion sites and subsequently undergoes force-induced conformational opening to recruit the actin-interacting protein vinculin. The conformational switch involves the talin R3 domain, which binds RIAM when closed and vinculin when open. Here, we apply pressure to R3 and measure 1H, 15N, and 13C chemical shift changes, which are fitted using a simple model, and indicate that R3 is only 50% closed: the closed form is a four-helix bundle, while in the open state helix 1 is twisted out. Strikingly, a mutant of R3 that binds RIAM with an affinity similar to wild-type but more weakly to vinculin is shown to be 0.84 kJ mol−1 more stable when closed. These results demonstrate that R3 is thermodynamically poised to bind either RIAM or vinculin, and thus constitutes a good mechanosensitive switch. [Display omitted] •An analysis of pressure-dependent data reveals chemical shifts of both states•The open state is 50% populated and has helix 1 opened out•Implies a stepwise opening of the 4-helix bundle in response to tension•Shows talin is thermodynamically poised for opening as a mechanosensitive switch Baxter et al. used high pressure to increase the population of the open state of the R3 domain of talin. They calculated chemical shifts of closed and open states, showing that the open state has helix 1 opened out, representing the start of force-dependent opening.