Abstract
Most peroxisomal matrix proteins are synthesized in cytosol with targeting signal at C- (PTS1) or N-terminus (PTS2). PTS1 and PTS2 proteins are recognized by receptors, Pex5p and Pex7p, respectively, and imported into peroxisomes by binding to the docking factor, Pex14p, on peroxisomal membrane. Catalase is highly accumulated in peroxisomes. Perhaps, there is a specific pathway for catalase because catalase has neither typical PTS1 nor PTS2.
We generated transgenic tobacco BY-2 cells in which Pex5p was suppressed by RNAi method, and observed subcellular localization of GFP-catalase fusion proteins. When the expression of Pex5p was suppressed, catalase could be imported into peroxisomes, suggesting that other proteins besides Pex5p are involved in catalase import. We isolated the proteins binding to tobacco catalase by yeast two-hybrid system, and analyzed the binding proteins. We also analyzed subcellular localization of catalase in the Pex14p mutant of Arabidisopsis to investigate whether Pex14p is involved in catalase import.
