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Matrix processing peptidase of mitochondria. Structure-function relationships
H Schneider1, M Arretz, E Wachter
1Institut für Physiologische Chemie, Physikalische Biochemie und Zellbiologie, Universität München, Federal Republic of Germany.
Abstract:
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.
Insights
Mitochondrial processing peptidase (MPP) and processing enhancing protein (PEP) cleave mitochondrial precursor proteins. Neurospora MPP
Area of Science:
- Mitochondrial biology
- Protein processing
- Molecular genetics
Background:
- Mitochondrial precursor proteins require proteolytic cleavage of targeting sequences.
- Mitochondrial processing peptidase (MPP) and processing enhancing protein (PEP) are key enzymes in this process.
Purpose of the Study:
- To determine the cDNA sequence of Neurospora MPP.
- To elucidate the structural and functional characteristics of Neurospora MPP and its relationship to PEP.
Main Methods:
- Expression cloning of Neurospora MPP cDNA.
- Sequence analysis and comparison with yeast MPP and PEP.
- Biochemical assays to determine enzyme activity and metal ion dependence.
Main Results:
- The cDNA sequence of Neurospora MPP was determined.
- Neurospora MPP exhibits a two-domain structure with similarity to yeast MPP and both yeast and Neurospora PEP.
- Four conserved cysteine residues were identified in Neurospora and yeast MPP.
- MPP activity is dependent on divalent metal ions and can be inactivated by sulfhydryl reagents.
- Both MPP and PEP are synthesized as precursors processed during mitochondrial import.
Conclusions:
- Neurospora MPP shares structural homology with related proteins, suggesting conserved functional mechanisms.
- Divalent metal ions and specific cysteine residues are crucial for MPP activity.
- The processing of MPP and PEP precursors highlights a coordinated import and maturation pathway within mitochondria.