Abstract
Most peroxisomal matrix proteins are synthesized in cytosol with a targeting signal PTS1 at C-terminus or PTS2 at N-terminus. They are recognized by receptors, Pex5p and Pex7p, respectively, and imported into peroxisomes by binding to the docking factor, Pex14p, on peroxisomal membrane. Catalase, peroxisomal enzyme, has neither typical PTS1 nor PTS2. Peroxisomal import system of catalase is unknown. The study using pumpkin catalase, Cat1, suggested that internal PTS1 like sequence 'QKL' is functional for targeting, but the interaction between Cat1 and Pex5p was distinct from typical PTS1. Then we analyzed subcellular localization of mRFP-Cat1 fusion protein in Pex5p-defficient Arabidopsis generated by RNAi. Inhibition of Cat1 import into peroxisome in Pex5p-deficient Arabidopsis suggests that Pex5p is involved in catalase import. By the analysis using Arabidopsis mutants, we revealed that Pex14p, Pex13p, Pex12p and Pex10p which are necessary for PTS1 and PTS2 import, are also necessary for catalase import.
