ATP-dependent chaperone that functions as an unfoldase. As part of the ClpXP protease complex, it recognizes specific protein substrates, unfolds them using energy derived from ATP hydrolysis, and then translocates them to the proteolytic subunit (CLPP) of the ClpXP complex for degradation (PubMed:11923310, PubMed:22710082, PubMed:28874591). Thanks to its chaperone activity, it also functions in the incorporation of the pyridoxal phosphate cofactor into 5- aminolevulinate synthase, thereby activating 5-aminolevulinate (ALA) synthesis, the first step in heme biosynthesis (PubMed:28874591). This chaperone is also involved in the control of mtDNA nucleoid distribution, by regulating mitochondrial transcription factor A (TFAM) activity (PubMed:22841477). {ECO:0000269|PubMed:11923310, ECO:0000269|PubMed:22710082, ECO:0000269|PubMed:22841477, ECO:0000269|PubMed:28874591}. This is the function of CLPX (caseinolytic mitochondrial matrix peptidase chaperone subunit X, Ensembl gene identifier ENSG00000166855).