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

Area of Science:

• Biophysics
• Statistical Mechanics
• Molecular Biology

Background:

• Protein folding landscapes are complex, with rare conformations often hidden at longer timescales.
• Enhanced sampling methods are computationally intensive for exploring these rare events.
• Experimental techniques need advancement to observe protein dynamics over extended periods.

Purpose of the Study:

• To investigate the timescale dependence of protein folding dynamics.
• To identify and characterize low-occurrence conformations in protein energy landscapes.
• To explore the role of these conformations in protein function and mechanotransduction.

Main Methods:

• Utilized single-molecule magnetic tweezers to observe over a million force-induced unfolding/refolding transitions of talin.
• Extended observation times from minutes to days to probe equilibrium dynamics.
• Applied fluctuation analysis to identify and characterize rare conformational states.

Main Results:

• Talin folding appears two-state at short timescales but reveals complex energy landscape signatures with extended observation.
• A finite number of well-defined, low-probability conformations were identified.
• Plausible structures for these rare states were proposed, linking them to vinculin binding.

Conclusions:

• Protein equilibrium dynamics are fundamentally dependent on the observation timescale.
• Extended timescale observations reveal hidden complexity in protein folding landscapes.
• Identified talin conformations may play a significant role in mechanotransduction via vinculin binding.