Force-dependent unfolding and folding dynamics of protein alpha-catenin modulation domains

α-catenin is an adhesion protein located at the cadherin-based cell-cell adherens junction.α-catenin cross-linksβ-catenin and actin fiber in the adhesion protein complex,and plays an important role in the formation and modulation of cell-cell adhesion.The central modulation domains can be unfolded to expose binding site of vinculin when stretching force is applied.Here,we studied the force-induced unfolding dynamics ofα-catenin modulation domains under different loading rates from which the unfolding distance of M2 and M3 domains is determined to be 5-7 nm,and an unfolding intermediate state is identified.We also found that the folding process of M1-M3 domains goes through different pathways with cooperativity.