ClpX Shifts into High Gear to Unfold Stable Proteins

Protein degradation by the ClpXP protease requires collaboration among the six AAA+ domains of ClpX. Using single-molecule optical tweezers, Sen et al. show that ClpX uses a coordinated succession of power strokes to translocate polypeptides in ATP-tunable bursts before reloading with nucleotide. This strategy allows ClpX to kinetically capture transiently unfolded intermediates.