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Published on: May 25, 2018
Mammalian pitrilysin: substrate specificity and mitochondrial targeting.
K Martin Chow1, O Gakh, I C Payne
1Department of Molecular and Cellular Biochemistry, University of Kentucky, B283 BBSRB, 741 South Limestone Street, Lexington, Kentucky 40536-0509, USA.
Biochemistry
|February 7, 2009
Summary
Mitochondrial metallopeptidase proteinase 1 (MP1) shows broad substrate specificity, preferring longer peptides. A 15-amino acid N-terminal sequence targets MP1 to mitochondria, crucial for its function.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Mitochondrial metallopeptidase proteinase 1 (MP1) is a key enzyme in mitochondrial protein processing.
- Understanding its substrate specificity and localization is vital for comprehending mitochondrial function.
Purpose of the Study:
- To investigate the substrate specificity of MP1.
- To identify the mitochondrial targeting signal of MP1.
Main Methods:
- Enzyme kinetics assays using physiological peptides.
- Analysis of MP1 cleavage sites compared to mitochondrial processing protease (MPP).
- Cell transfection studies (NT2 and HepG2 cells) with MP1 and its mutants, including fusion with green fluorescent protein (GFP).
Main Results:
- MP1 exhibits broad substrate specificity, with a preference for longer peptides (≥13 residues) showing lower K(m) and k(cat) values.
- Cleavage sites of MP1 partially overlap with MPP, but MP1 does not process citrate synthase precursor.
- MP1 cleaves the prepeptide from precitrate synthase.
- A 15-amino acid N-terminal sequence acts as a mitochondrial targeting signal, directing MP1 and GFP fusion proteins to mitochondria.
Conclusions:
- The N-terminus of MP1 contains a functional mitochondrial targeting signal.
- MP1's substrate specificity suggests a role in processing specific mitochondrial peptides, potentially including prepeptides.
- MP1 localization is critical for its function within the mitochondria.
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