ATP-dependent specificity component of the Clp protease. It directs the protease to specific substrates. Can perform chaperone functions in the absence of ClpP (By similarity). Probably the major protease that degrades proteins tagged by trans-translation (PubMed:11395451). Component of the ClpX-ClpP complex. Forms a hexameric ring that, in the presence of ATP, binds to fourteen ClpP subunits assembled into a disk-like structure with a central cavity, resembling the structure of eukaryotic proteasomes. By heat shock. No degradation of trans-translationally tagged-peptides. Belongs to the ClpX chaperone family.