HsClpX and HsClpP are encoded by the nuclear genesCLPX (NCBI GeneID 10845) located on chromosome 15 andCLPP (NCBI GeneID 8192) located on chromosome 19.Their domain architecture is shown in Figure 1A. HsClpX is633 amino acid residues in length and consists primarily of theAAA+ domain preceded by a zinc-binding domain (ZBD) forsubstrate protein recognition.4 At the N-terminus of HsClpX isa mitochondrial targeting sequence (MTS) that is required forits translocation into the mitochondrial matrix.5 HsClpP is 277amino acid residues in length and consists almost entirely ofthe serine protease domain. Like HsClpX, a MTS is positioned at the N-terminus of HsClpP for mitochondrial translocation