Required, in concert with mitochondrial Hsp70 (SSC1), 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. Its main role may be maintaining the molecular chaperone SSC1 in a soluble and functional state. Also required for the efficient degradation of proteins by matrix protease PIM1, independent on its protein remodeling activity. Homohexamer, forming a ring with a central pore. The hexamer is stabilized by high protein concentrations and by ADP or ATP. Oligomerization influences ATP hydrolysis activity. By heat stress. Expressed at a higher level in respiring cells than in fermenting cells (at protein level). Has 2 AAA ATPase type nucleotide-binding domains (NBDs) per monomer. NBD1 is primarily responsible for ATP hydrolysis. NBD2 is crucial for oligomerization. Present with 2990 molecules/cell in log phase SD medium. Belongs to the ClpA/ClpB family.