ATP-dependent specificity component of the Clp protease. Uses cycles of ATP binding and hydrolysis to unfold proteins and translocate them to the ClpP protease. It directs the protease to specific substrates both with and without the help of adapter proteins such as SspB. Participates in the final steps of RseA-sigma-E degradation, liberating sigma-E to induce the extracytoplasmic-stress response. It may bind to the lambda O substrate protein and present it to the ClpP protease in a form that can be recognized and readily hydrolyzed by ClpP. Can perform chaperone functions in the absence of ClpP. Binds 1 Zn(2+) ion per subunit. 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. Interacts with Mu phage DDE-recombinase A; this interaction remodels the viral transpososome for replication. By heat shock. Part of the clpP-clpX operon, clpX can be expressed individually from its own promoter. Delayed and decreased induction of the extracytoplasmic-stress response. Belongs to the ClpX chaperone family.