Direct interaction and determination of binding domains among peroxisomal import factors in Arabidopsis thaliana

We analyzed the role of Arabidopsis orthologues of human Pex14p, Pex5p and Pex7p that are central components of peroxisomal protein import machinery. Immunoblot analysis showed that, 4fPexl4p and AtPex5p were present in most organs in Arabidopsis, suggesting that these factors play a role in the main protein import pathways for plant peroxisomes. Two-hybrid analysis showed that AtPex14p interacted with AtPex5p, but not with AtPex7p. In addition, AtPex7p was bound to AtPex5p, indicating that the PTS2 pathway depends on the PTS1 pathway in Arabidopsis. Further analysis showed that the nine WXXXF/Y repeats in the amino acids sup231 K- sup450 D and sup1 M- sup230 V of AtPex5p are bound to two N-terminal domains, amino acids sup58 I- sup65 L and sup78 R- sup97 R of AtPexl4p and the C-terminal amino acids sup266 Y- sup317 S of AtPex7p, respectively. Since the binding domains of AtPex5p to AtPexl4p and AtPex7p do not overlap, AtPexl4p, AtPex5p and AtPex7p might form their complex and function cooperatively in peroxisomal protein import.