Enhanced statistical sampling reveals microscopic complexity in the talin mechanosensor folding energy landscape

Rafael Tapia-Rojo*, Marc Mora, Stephanie Board, Jane Walker, Rajaa Boujemaa-Paterski, Ohad Medalia, Sergi Garcia-Manyes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)
59 Downloads (Pure)

Abstract

Statistical mechanics can describe the major conformational ensembles determining the equilibrium free-energy landscape of a folding protein. The challenge is to capture the full repertoire of low-occurrence conformations separated by high kinetic barriers that define complex landscapes. Computationally, enhanced sampling methods accelerate the exploration of molecular rare events. However, accessing the entire protein’s conformational space in equilibrium experiments requires technological developments to enable extended observation times. We used single-molecule magnetic tweezers to capture over a million individual transitions as a single talin protein unfolds and refolds under force in equilibrium. When observed at classically probed timescales, talin folds in an apparently uncomplicated two-state manner. As the sampling time extends from minutes to days, the underlying energy landscape exhibits gradually larger signatures of complexity, involving a finite number of well-defined rare conformations. Fluctuation analysis allows us to propose plausible structures of each low-probability conformational state. The physiological relevance of each distinct conformation can be connected to the binding of the cytoskeletal protein vinculin, suggesting an extra layer of complexity in talin-mediated mechanotransduction. More generally, our experiments directly test the fundamental notion that equilibrium dynamics depend on the observation timescale.

Original languageEnglish
Pages (from-to)52–60
JournalNature Physics
Early online date7 Nov 2022
DOIs
Publication statusE-pub ahead of print - 7 Nov 2022

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