PMID:21529717

Citation	Maillard, RA, Chistol, G, Sen, M, Righini, M, Tan, J, Kaiser, CM, Hodges, C, Martin, A and Bustamante, C (2011) ClpX(P) generates mechanical force to unfold and translocate its protein substrates. Cell 145:459-69
Abstract	AAA(+) unfoldases denature and translocate polypeptides into associated peptidases. We report direct observations of mechanical, force-induced protein unfolding by the ClpX unfoldase from E. coli, alone, and in complex with the ClpP peptidase. ClpX hydrolyzes ATP to generate mechanical force and translocate polypeptides through its central pore. Threading is interrupted by pauses that are found to be off the main translocation pathway. ClpX's translocation velocity is force dependent, reaching a maximum of 80 aa/s near-zero force and vanishing at around 20 pN. ClpX takes 1, 2, or 3 nm steps, suggesting a fundamental step-size of 1 nm and a certain degree of intersubunit coordination. When ClpX encounters a folded protein, it either overcomes this mechanical barrier or slips on the polypeptide before making another unfolding attempt. Binding of ClpP decreases the slip probability and enhances the unfolding efficiency of ClpX. Under the action of ClpXP, GFP unravels cooperatively via a transient intermediate.
Links	PubMed PMC3686100 Online version:10.1016/j.cell.2011.04.010
Keywords	Adenosine Triphosphatases/metabolism; Biomechanics; Endopeptidase Clp/metabolism; Escherichia coli/enzymology; Escherichia coli/metabolism; Escherichia coli Proteins/metabolism; Green Fluorescent Proteins/analysis; Green Fluorescent Proteins/metabolism; Molecular Chaperones/metabolism; Protein Denaturation; Protein Folding; Protein Transport
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:CLPX		GO:0043335: protein unfolding	ECO:0000314:		P		Figure 4 - ClpX unfolds GFP.	complete CACAO 9068
ECOLI:CLPX	involved_in	GO:0043335: protein unfolding	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete
ECOLI:CLPP		GO:0043335: protein unfolding	ECO:0000314:		P		Figure 4 - ClpP complexes with ClpX to unfold GFP during proteolysis.	complete CACAO 9070
ECO27:CLPX		GO:0043335: protein unfolding	ECO:0000314:		P		Figure 4 - ClpX unfolds GFP.	complete CACAO 9058
ECO27:B7UJR0		GO:1901800: positive regulation of proteasomal protein catabolic process	ECO:0000314:		P		Figure 6 - With ClpP in complex with ClpX, slippage of the protein occurs much less and thus the ClpP works to positively regulate the catabolic process of GFP.	complete CACAO 9055

References

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