Poster: Protein Targeting & Vesicular Trafficking

Abs # 1179: Analysis of peroxisomal biogenesis factors in Arabidopsis thaliana

Presenter:	Nito, Kazumasa , nitokaz@nibb.ac.jp
Authors	Nito, Kazumasa  (A)   Hayashi, Makoto  (A)   Nishimura, Mikio  (A)
Affiliations:	(A): National Institute for Basic Biology
Web Site:	http://www.nibb.ac.jp/index.html

Plant peroxisomes are known to differentiate into at least three classes, namely glyoxysomes, leaf peroxisomes and unspecialized peroxisomes. These different peroxisomes possess a different set of enzymes that is related to special function, and transform into one another in various developmental stages of higher plants. Most peroxisomal proteins have been known to contain either PTS1- or PTS2- transport signal within the molecules. We analyzed the role of Arabidopsis Pex14p, Pex5p and Pex7p that are central components of peroxisomal protein import machinery. AtPex14p was identified as a peroxisomal membrane protein from our mutant study. AtPex5p and AtPex7p are Arabidopsis orthologues of human Pex5p and Pex7p that are characterized as cytosolic PTS1- and PTS2-receptor, respectively. 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 ²³¹K-⁴⁵⁰D and N-terminal ¹M-²³⁰V of AtPex5p are bound to two N-terminal domains, ⁵⁸I-⁶⁵L and ⁷⁸R-⁹⁷R of AtPex14p and the C-terminal ²⁶⁶Y-³¹⁷S of AtPex7p, respectively. Since the binding domains of AtPex5p to AtPex14p and AtPex7p do not overlap, newly synthesized peroxisomal proteins are recognized by AtPex5p or AtPex7p in the cytosol, and then AtPex14p, AtPex5p and AtPex7p might form their complex on peroxisomal membrane and function cooperatively in peroxisomal protein import.