The carboxy-terminal end of glycolate oxidase directs a foreign protein into tobacco leaf peroxisomes.

The carboxy-terminal residues of several peroxisomal proteins were shown to act as a peroxisomal targetting signal. This study was conducted to test whether the C-terminus of glycolate oxidase, a key enzyme in the glycolate metabolism pathway, is functioning as a targetting signal that directs proteins into plant leaf peroxisomes. A chimeric gene coding for a fusion protein composed of the C-terminal-truncated beta-glucuronidase, a synthetic linker of four amino acids and the last six C-terminal amino acids of glycolate oxidase, was constructed. Transformation of tobacco plants with the chimeric gene resulted in expression of beta-glucuronidase enzymic activity. About 50% of the transgenic beta-glucuronidase activity was localized to the peroxisomes. The results indicate that the six C-terminal amino acid residues of glycolate oxidase act as a targetting signal that is recognized by leaf peroxisomes.