ATP-dependent zinc metalloprotease. Plays a role in the formation and regulation of the mitochondrial permeability transition pore (mPTP) and its proteolytic activity is dispensable for this function (PubMed:26387735). Binds 1 zinc ion per subunit. Forms heterooligomers with AFG3L1 and AFG3L2. Component of the mitochondrial permeability transition pore complex (mPTPC), at least composed of SPG7, VDAC1 and PPIF. Interacts with AFG3L2; the interaction is required for the efficient assembly of mitochondrial complex I. Interacts with AFG3L1. Interacts with MAIP1. Interacts with VDAC1 and PPIF. Upon import into the mitochondrion, the N-terminal transit peptide is cleaved by the mitochondrial-processing peptidase (MPP) to generate an intermediate form which undergoes a second proteolytic cleavage mediated by proteases AFG3L1 and/or AFG3L2 removing an additional N-terminal fragment to generate the proteolytically active mature form. In the N-terminal section; belongs to the AAA ATPase family. In the C-terminal section; belongs to the peptidase M41 family.