Required, in concert with mitochondrial Hsp70, for the dissociation, resolubilization and refolding of aggregates of damaged proteins in the mitochondrial matrix after heat stress. May extract proteins from aggregates by unfolding and threading them in an ATP-dependent process through the axial channel of the protein hexamer, after which they can be refolded by the Hsp70 chaperone system. Required for resumption of mitochondrial respiratory function, DNA synthesis and morphology after heat stress (By similarity). Homohexamer, forming a ring with a central pore. Has 2 AAA ATPase type nucleotide-binding domains (NBDs) per monomer. NBD1 is primarily responsible for ATP hydrolysis. NBD2 is crucial for oligomerization (By similarity). Belongs to the ClpA/ClpB family.