Polypeptide loop translocation by single ClpB disaggregases

Re-dissolving protein aggregates is crucial to cells, but the
molecular basis has remained untested in direct experiments.
Using combined optical tweezers and single-molecule fluo-
rescence detection, we show that the disaggregase ClpB ex-
trudes loops of protein chains through its central pore, and
hence forcibly extracts protein chains from aggregates. The
data reveal notable processivity, power, step-dynamics, and
switching between translocation modes. Protein disaggre-
gation can thus be highly deterministic and energy-driven
process, while polypeptide loop extrusion may be exploited
by other systems including p97/cdc48