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First published online 8 August 2006
doi: 10.1242/jcs.03100
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Research Article |
Department of Biology, Faculty of Sciences, Kyushu University Graduate School, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
* Author for correspondence (e-mail: yfujiscb{at}mbox.nc.kyushu-u.ac.jp)
Accepted 14 June 2006
The peroxin Pex19p functions in peroxisomal membrane assembly. Here we mapped functional domains of human Pex19p comprising 299 amino acids. Pex19p mutants deleted in the C-terminal CAAx farnesylation motif, the C-terminal 38 amino acid residues and the N-terminal 11 residues, maintained peroxisome-restoring activity in pex19 cells. The sequence 12-261 was essential for re-establishing peroxisome activity. Pex19p was partly localized to peroxisomes but mostly localized in the cytosol. Pex19p interacted with multiple membrane proteins, including the other two membrane biogenesis peroxins, Pex3p and Pex16p, those involved in matrix protein import such as Pex14p, Pex13p, Pex10p, and Pex26p, peroxisome morphogenesis factor Pex11pß, and a PMP70 peroxisome-targeting signal region at residues 1-123. In yeast two-hybrid assays, Pex10p and Pex11pß interacted only with full-length Pex19p. Of various truncated Pex19p variants active in translocating to peroxisomes, the mutants with the shortest sequence (residues 12-73 and 40-131) were localized to peroxisomes and competent in binding to Pex3p. Furthermore, membrane peroxins were initially discernible in a cytosolic staining pattern in pex19 cells only when co-expressed with Pex19p and were then localized to peroxisomes in a temporally differentiated manner. Pex19p probably functions as a chaperone for membrane proteins and transports them to peroxisomes by anchoring to Pex3p using residues 12-73 and 40-131.
Key words: Peroxisome biogenesis, Membrane assembly, Pex19p, Chaperone, Transporter
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