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  • Title: In vitro transport of membrane proteins to peroxisomes by shuttling receptor Pex19p.
    Author: Matsuzono Y, Fujiki Y.
    Journal: J Biol Chem; 2006 Jan 06; 281(1):36-42. PubMed ID: 16280322.
    Abstract:
    The peroxin Pex19p comprising 299 amino acids functions in peroxisomal membrane assembly. We here developed a cell-free system for transport of membrane proteins to peroxisomes. Pex19p interacts with multiple membrane peroxins, including other membrane biogenesis peroxins, Pex16p and Pex26p, involved in matrix protein import. Cell-free synthesized, 35S-labeled Pex19p was targeted to subcellular fractions containing peroxisomes from Chinese hamster ovary-K1 cells as well as peroxisomes isolated from rat liver in an ATP-dependent manner. Such translocation was also reproduced with in vitro synthesized 35S-Pex16p with two transmembrane segments and C-tail anchor-type 35S-Pex26p, upon incubation with 35S-Pex19p in the reaction mixtures containing isolated peroxisomes. The transported 35S-Pex16p and 35S-Pex26p were integrated into membranes as assessed by the sodium carbonate extraction method. Peroxisome-associated and partly Na2CO3-resistant 35S-Pex19p was released to the cytosolic fraction upon incubation in the absence of ATP, whereas 35S-Pex16p and 35S-Pex26p remained in the membranes. Furthermore, not only 35S-Pex19p but also 35S-Pex19p complexes each with 35S-Pex16p and 35S-Pex26p were bound to 35S-Pex3p in vitro. Together, these results strongly suggested that Pex19p translocates the membrane peroxins from the cytosol to peroxisomes in an ATP- and Pex3p-dependent manner and then shuttles back to the cytosol.
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