Cryo-electron microscopy reconstructions of vinculin (Vt) and metavinculin (MVt) tail domains bound to F-actin.
MVt and Vt undergo partial unfolding transitions upon actin engagement.
This partial unfolding transition is required for actin bundling by Vt.
Tension will favor the partially unfolded, actin-bound state, reinforcing adhesion through vinculin.