Thiolase mRNA translated in vitro yields a peptide with a putative N-terminal presequence

Area of Science:

• Plant biochemistry
• Molecular biology
• Cell biology

Background:

• Thiolase is a key enzyme in fatty acid oxidation, localized in plant glyoxysomes or peroxisomes.
• In cucumber cotyledons, thiolase processing involves proteolytic modification during its translocation into glyoxysomes.

Purpose of the Study:

• To isolate and characterize the full-length cDNA encoding the thiolase precursor in cucumber.
• To investigate the structural similarities and potential targeting mechanisms of plant thiolase.

Main Methods:

• Isolation of a full-length cDNA clone for cucumber thiolase precursor.
• Size comparison of in vitro synthesized precursor and mature glyoxysomal thiolase subunit.
• Sequence homology analysis with fungal, human, and bacterial thiolases, and other peroxisomal proteins.

Main Results:

• A cDNA encoding a 48,539 Da thiolase precursor was isolated.
• The plant thiolase precursor shares 40-47% identity with fungal and human counterparts.
• A 34-amino acid N-terminal extension in the plant precursor suggests a targeting sequence similar to other peroxisomal proteins.

Conclusions:

• Cucumber thiolase is synthesized as a precursor that undergoes proteolytic processing for glyoxysomal targeting.
• The N-terminal extension likely functions as a cleavable targeting signal for peroxisomal import.
• Comparative analysis highlights conserved features in peroxisomal enzyme targeting across different species.