Isolation and nucleotide sequence of a cDNA clone encoding rat mitochondrial malate dehydrogenase

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Mitochondrial malate dehydrogenase (mMDH) is crucial for the citric acid cycle.
• Understanding the precursor protein sequence is key to elucidating mitochondrial import mechanisms.

Purpose of the Study:

• To determine the complete amino acid sequence of the rat mitochondrial malate dehydrogenase (mMDH) precursor.
• To characterize the N-terminal transit peptide responsible for mitochondrial import.

Main Methods:

• Screening of a rat atrial cDNA library using a synthetic oligodeoxynucleotide probe.
• Isolation and sequencing of a full-length cDNA clone encoding pre-mMDH.

Main Results:

• The complete amino acid sequence of pre-mMDH was determined from a 1.2 kb cDNA clone.
• A 24-amino acid N-terminal extension (transit peptide) was identified, directing mitochondrial import.
• The mature mMDH protein consists of 314 amino acids after cleavage of the transit peptide.
• The transit peptide exhibits polar and basic amino acid composition and homology with other mitochondrial targeting sequences.

Conclusions:

• The identified transit peptide is critical for targeting mMDH to the mitochondrial matrix.
• The sequence data provides insights into the post-translational modification and import of mMDH.