Compliant mechanical response of the ultrafast folding protein EnHD under force

Abstract Ultrafast folding proteins have become an important paradigm in the study of protein dynamics. Due to their low energetic barriers and fast kinetics, they are amenable for by both experiment simulation. However, single molecule force spectroscopy experiments on these systems challenging as do not provide mechanical fingerprints characteristic more mechanically stable proteins, which makes it difficult extract information about dynamics molecule. Here, we investigate unfolding ultrafast Engrailed Homeodomain (EnHD) single-molecule atomic microscopy experiments. Constant speed EnHD result featureless transitions typical compliant proteins. force-ramp mode recover sigmoidal curves that interpret a very folds unfolds many times over marginal barrier. This is supported simple theoretical model coarse-grained molecular simulations. Our results show ability modulate