Matrix processing peptidase of mitochondria

The mitochondrial processing peptidase (MPP) and the processing
enhancing protein (PEP) cooperate in the proteolytic cleavage of
matrix targeting sequences from nuclear-encoded mitochondrial
precursor proteins. We have determined the cDNA sequence of
Neurospora MPP after expression cloning. MPP appears to contain two
domains of approximately equal size which are separated by a
loop-like sequence. Considerable structural similarity exists to
the recently sequenced yeast MPP as well as to Neurospora and yeast
PEP. Four cysteine residues are conserved in Neurospora and yeast
MPP. Inactivation of MPP can be achieved by using sulfhydryl
reagents. MPP (but not PEP) depends on the presence of divalent
metal ions for activity. Both MPP and PEP are synthesized as
precursors containing matrix targeting signals which are processed
during import into mitochondria by the mature forms of MPP and PEP.