User:Chiron Zebra/Mitochondrial processing peptidase

Mitochondria import the majority of their proteins from the cell cytosol, in order to achieve this many mitochondrial proteins encode a short targeting signal which directs them to the mitochondrion and through its preprotein translocase machinery. Mitochondrial proteins which reach the inner most mitochondrial compartment, the matrix, often undergo proteolytic cleavage of the targeting signal, performed by the Mitochondrial Processing Peptidase (MPP), this is often necessary for the maturation of the preprotein to its functional form or to reveal additional targeting sequences.

In most eukaryotes, the MPP consists of two subunits, an α and β subunit which bind together to form a heterodimeric complex. In humans these are the genes PMPCA and PMPCB. The subunits of the MPP are highly conserved, and have shown to be interoperable between species, homologues to MPPs are also found in eukaryotes whose mitochondria have evolved into divergent organelles, though in the case of Trichomonas the processing peptidase complex appears to be made of two β subunits. The origins of the mitochondrial processing peptidases are thought to be prokaryotic in origin, possibly originating in the endosymbiont which developed into the mitochondrion, this hypothesis has been supported by the discovery of a bacterial signal peptidase in Rickettsia, an organism thought to be a closely related to the mitochondrial progenitor. Experimentally this peptidase was shown to cleave signal sequences from mitochondrial proteins.

Human Proteins
PMPCA, PMPCB