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The plant PTS1 receptor: similarities and differences to its human and yeast counterparts
Author(s) -
Wimmer Christine,
Schmid Markus,
Veenhuis Marten,
Gietl Christine
Publication year - 1998
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1998.00320.x
Subject(s) - peroxisome , glyoxysome , peroxisomal targeting signal , biology , biochemistry , tetratricopeptide , immunogold labelling , yeast , cytosol , saccharomyces cerevisiae , microbiology and biotechnology , receptor , gene , genetics , enzyme , antibody
Summary Two targeting signals, PTS1 and PTS2, mediate import of proteins into the peroxisomal matrix. We have cloned and sequenced the watermelon (Citrullus vulgaris) cDNA homologue to the PTS1 receptor gene (PEX5). Its gene product, CvPex5p, belongs to the family of tetratricopeptide repeat (TPR) containing proteins like the human and yeast counterparts, and exhibits 11 repeats of the sequence W‐X 2 ‐(E/S)‐(Y/F/Q) in its N‐terminal half. According to fractionation studies the plant Pex5p is located mainly in the cytosolic fraction and therefore could function as a cycling receptor between the cytosol and glyoxysomes, as has been proposed for the Pex5p of human and some yeast peroxisomes. Transformation of theHansenula polymorphaperoxisome deficient pex5 mutant with watermelon PEX5 resulted in restoration of peroxisome formation and the synthesis of additional membranes surrounding the peroxisomes. These structures are labeled in immunogold experiments using antibodies against theHansenula polymorphaintegral membrane protein Pex3p, confirming their peroxisomal nature. The plant Pex5p was localized by immunogold labelling mainly in the cytosol of the yeast, but also inside the newly formed peroxisomes. However, import of the PTS1 protein alcohol oxidase is only partially restored by CvPex5p.