Has a dual role in the assembly of mitochondrial ATPase. Acts as a protease that removes N-terminal residues of mitochondrial ATPase CF(0) subunit 6 at the intermembrane space side. Also involved in the correct assembly of the membrane-embedded ATPase CF(0) particle, probably mediating association of subunit 6 with the subunit 9 ring (By similarity). Associates loosely with the inner membrane. Belongs to the peptidase M76 family.