Peptidase, Mitochondrial Processing Beta (PMPCb)

PMPCb is a member of the peptidase M16 family and encodes a protein with a zinc-binding motif. This protein is located in the mitochondrial matrix and catalyzes the cleavage of the leader peptides of precursor proteins newly imported into the mitochondria, though it only functions as part of a heterodimeric complex.In in vitro assays, MPPB bound frataxin, which was cleaved by the reconstituted MPP heterodimer. MPP cleavage of frataxin resulted in an intermediate form, comprising amino acids 41 to 210, which was processed further to the mature form. In vitro and in vivo experiments suggested that 2 C-terminal missense mutations found in FRDA patients, I151F  and G130V, modulated interaction with MPP-beta, resulting in a slower maturation process at the normal cleavage site.