PTS2 Co-receptors: Diverse proteins with common features

Abstract

One feature of the PTS2 import pathway is the separation of the roles of the PTS receptor between two proteins. Pex7p alone is insufficient to act as the receptor for the import cycle for peroxisomal matrix proteins. In all cases, Pex7p needs a PTS2 co-receptor to form an import-competent PTS2 receptor complex together with the PTS2 cargo. We provide an overview of the proteins that have been identified as PTS2 co-receptors and discuss their proposed functions.

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

“…In mammals and plants but not in yeasts/fungi, Pex5p is also in charge of targeting PTS2-containing proteins to the organelle matrix (4). In this case, however, the Pex5p-PTS2 interaction is not direct but rather bridged by Pex7p, the socalled PTS2 receptor (5).…”

Identification of Ubiquitin-specific Protease 9X (USP9X) as a Deubiquitinase Acting on Ubiquitin-Peroxin 5 (PEX5) Thioester Conjugate

“…In mammals, plants, and many other organisms, both PTS1-and PTS2-containing proteins are targeted to the organelle by PEX5, the socalled peroxisomal shuttling receptor (4 -7). The PEX5-PTS1 interaction is direct, whereas PTS2-containing proteins bind PEX5 via the adaptor protein PEX7 (8,9).…”

Molecular Mechanisms and Physiological Significance of Organelle Interactions and Cooperation

“…The primary docking of Pex5 is driven by a lipid-protein interaction (Kerssen et al, 2006), but the functional interaction is dependent on specific sequences within Pex5 that mediate the interaction with proteins of the DC (Saidowsky et al, 2001;Otera et al, 2002). In contrast, Pex7 cannot move to the peroxisomal surface by itself, but requires the interaction with a co-receptor protein, which encodes the sequence elements required for the interaction with the proteins of the docking complex (Schliebs and Kunau, 2006;Grunau et al, 2009;Kunze et al, 2015). This co-receptor function for Pex7 is exerted in many organisms (metazoa and plants) by the PTS1 receptor Pex5 (Braverman et al, 1998;Otera et al, 1998;Khan and Zolman, 2010), whereas in fungi independent proteins exist for this function (Purdue et al, 1998;Titorenko et al, 1998).…”