Pex14p is a member of the protein linkage map of Pex5p

Abstract

To identify members of the translocation machinery for peroxisomal proteins, we made use of the two‐hybrid system to establish a protein linkage map centered around Pex5p from Saccharomyces cerevisiae, the receptor for the C‐terminal peroxisomal targeting signal (PTS1). Among the five interaction partners identified, Pex14p was found to be induced under conditions allowing peroxisome proliferation. Deletion of the corresponding gene resulted in the inability of yeast cells to grow on oleate as well as the absence of peroxisomal structures. The PEX14 gene product of ∼38 kDa was biochemically and ultrastructurally demonstrated to be a peroxisomal membrane protein, despite the lack of a membrane‐spanning domain. This protein was shown to interact with itself, with Pex13p and with both PTS receptors, Pex5p and Pex7p, indicating a central function for the import of peroxisomal matrix proteins, either as a docking protein or as a releasing factor at the organellar membrane.

Peroxisomal Targeting Signal Receptor Pex5p Interacts with Cargoes and Import Machinery Components in a Spatiotemporally Differentiated Manner: Conserved Pex5p WXXXF/Y Motifs Are Critical for Matrix Protein Import

“…In yeast, Pex5p binds not only Pex14p but also the SH3 domain of Pex13p, implying that both serve as a docking receptor for Pex5p (3,5,7,13,14,21,22). On the other hand, the interaction between Pex5p and Pex13p in mammalian cells was not established.…”

Pex22p of Pichia pastoris, Essential for Peroxisomal Matrix Protein Import, Anchors the Ubiquitin-conjugating Enzyme, Pex4p, on the Peroxisomal Membrane

“…If Pex4p and/or Pex22p were missing, the import complex might lose its ability to function, due to incorrect stoichiometry, leading to a block of matrix protein import, and this could in turn lead to an instability of Pex5p. Several proteins of the import complex could be affected by Pex22p and Pex4p, including Pex13p (Albertini et al, 1997;Elgersma et al, 1996;Erdmann and Blobel, 1996;Gould et al, 1996), Pex14p (Albertini et al, 1997;Brocard et al, 1997;Fransen et al, 1998), or Pex17p (Huhse et al, 1998). Pex13p is stable in ⌬pex4 or ⌬pex22 strains (data not shown) and Pex5p is stable in a P. pastoris ⌬pex13 strain .…”

“…The localization of these two receptors is still controversial. It seems, however, that both receptors are localized to the cytosol and peroxi-100 somes, suggesting that the receptors shuttle from the cytoplasm to the peroxisomes, where they bind to the tightly associated peroxisomal membrane protein Pex13p (Girzalsky et al, 1999) and Pex14p (Albertini et al, 1997;Brocard et al, 1997;Fransen et al, 1998). Pex5p and Pex7p, as well as Pex14p, are in a complex with another peripheral peroxisomal membrane protein, Pex17p (Huhse et al, 1998).…”

Mutants of theYarrowia lipolytica PEX23Gene Encoding an Integral Peroxisomal Membrane Peroxin Mislocalize Matrix Proteins and Accumulate Vesicles Containing Peroxisomal Matrix and Membrane Proteins

“…Although separation of these two matrix protein pathways exists at this initial stage, convergence of the two pathways has been proposed to occur at the level of Pex14p, an integral peroxisomal membrane peroxin that has been demonstrated to bind both Pex5p and Pex7p (Albertini et al, 1997;Brocard et al, 1997;Huhse et al, 1998;Girzalsky et al, 1999;Shimizu et al, 1999). Pex13p, another peroxisomal integral membrane peroxin that was initially identified as the docking protein for the PTS1 receptor (Elgersma et al, 1996a;Erdmann and Blobel, 1996;Gould et al, 1996), has also been shown recently to bind the PTS2 receptor and to be required for the peroxisomal association of Pex14p (Girzalsky et al, 1999), suggesting that the point of convergence for the PTS1-and PTS2-dependent protein import pathways is at the level of the peroxisomal membrane and consists of a protein complex that contains both Pex13p and Pex14p.…”