The general mitochondrial matrix processing protease from rat liver: structural characterization of the catalytic...

Area of Science:

• Mitochondrial biology
• Protease biochemistry
• Molecular genetics

Background:

• Mitochondrial protein import requires processing of precursor proteins.
• Mitochondrial matrix processing proteases cleave amino-terminal leader peptides.
• The general matrix processing protease (GMPP) is crucial for this process.

Purpose of the Study:

• To characterize the general matrix processing protease from rat liver mitochondria.
• To determine the primary structure of the 55-kDa catalytic subunit of GMPP.

Main Methods:

• Protein sequencing of the mature amino terminus and tryptic peptides.
• Polymerase chain reaction (PCR) amplification of rat liver RNA to synthesize a cDNA probe.
• Screening of a rat liver cDNA library to obtain a nearly full-length clone.

Main Results:

• The final enzyme preparation contained 55-kDa and 52-kDa subunits.
• The cDNA clone encodes a 508-amino acid precursor protein, including a 16-amino acid leader peptide.
• The mature 55-kDa subunit shows 36% identity to yeast and fungal mitochondrial processing peptidases.
• A conserved negatively charged alpha-helix was identified in the N-terminal half of the mature subunit.

Conclusions:

• The characterized 55-kDa subunit is the catalytically active component of rat liver GMPP.
• The identified structural features may play a role in recognizing and binding mitochondrial precursor proteins.
• This study provides insights into the molecular mechanisms of mitochondrial protein import.