The N-terminal Half of the Peroxisomal Cycling Receptor Pex5p is a Natively Unfolded Domain

Abstract

Targeting of most newly synthesised peroxisomal matrix proteins to the organelle requires Pex5p, the so-called PTS1 receptor. According to current models of peroxisomal biogenesis, Pex5p interacts with these proteins in the cytosol, transports them to the peroxisomal membrane and catalyses their translocation across the membrane. Presently, our knowledge on the structural details behind the interaction of Pex5p with the cargo proteins is reasonably complete. In contrast, information regarding the structure of the Pex5p N-terminal half (a region containing its peroxisomal targeting domain) is still limited. We have recently observed that the Stokes radius of this Pex5p domain is anomalously large, suggesting that this portion of the protein is either a structured elongated domain or that it adopts a low compactness conformation. Here, we address this issue using a combination of biophysical and biochemical approaches. Our results indicate that the N-terminal half of Pex5p is best described as a natively unfolded premolten globule-like domain. The implications of these findings on the mechanism of protein import into the peroxisome are discussed.

Getting a camel through the eye of a needle: the import of folded proteins by peroxisomes

“…Binding of PTS1-containing cargo to the receptor is essential for import of the receptor-cargo complex, which can be rationalized in terms of the conformational change required to expose the N-terminal docking module which appears to be a natively unfolded domain (Carvalho et al, 2006). The N-and C-terminal regions of mammalian PEX5S without a bound ligand have been shown to interact with each other by a pull-down assay.…”

Members of the E2D (UbcH5) Family Mediate the Ubiquitination of the Conserved Cysteine of Pex5p, the Peroxisomal Import Receptor

“…these proteins are sequestered by adding to the import reactions a vast excess of a recombinant protein comprising only the cargo protein-binding domain of Pex5p (TPRs-Pex5p), then insertion of Pex5p is no longer possible (46). As shown in Fig.…”

Structural Insights into Cargo Recognition by the Yeast PTS1 Receptor

“…Functional and structural data revealed that Pex5p includes two separated, functionally distinct domains. The N-terminal domain is intrinsically disordered and capable to mediate all transport steps of the receptor cycle, including docking and pore formation as well as dislocation from the peroxisomal membrane (13)(14)(15). The C-terminal domain of the receptor consists of an array of tetratricopeptide repeat (TPR) domains and directly binds the PTS1 motif (16).…”