Structural and functional study of peroxins

Project Manager: Yoshiteru SATO
(Faculty of Sciences, Post-doctoral Fellow)

■Traffic mechanism for peroxisomal matrix proein

　　In peroxisomal matrix, there are several hundreds of enzymes. These enzymes are imported to peroxisome by peroxisomal protein, Pex5p. This mechanism goes as described below.

1　.Ribosome synthesizes matrix protein in cytosol.
2.　Pex5p binds to matrix protein by recognizing peroxisome
　　targeting signal.
3.　Pex14p and Pex13p form entrance of peroxisome. Pex5p and
　　matrix protein reach the entrance by Pex5p and Pex14p interaction.
4.　Pex5p release the matrix protein in to the matrix. Subsequently, Pex5p is
　　ubiquitinated by Pex2p, Pex10p and Pex12p complex.
5.　Ubiquitinated Pex5p is led by p40 to Pex1p and Pex6p complex.
6.　Pex1p and Pex6p complex exports Pex5p into cytosol by using ATP
　　energy.
7.　Exported Pex5p is reused for the import of matrix protein.

In this study, I focused on Pex1p and p40 whose functional mechanisms are unclear yet.

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■Highly purified proteins for crystallographic analysis

　　In this study, I am performing crystallographic analysis of Pex1p and p40 which work for peroxisomal matrix protein import. During the last year, I succeeded to overexpress of these proteins by using E. coli and purify as highly pure protein by using three procedures. Now, initial screening for crystallization is ongoing.