PEX5cargo

Pex5cargo is a term used in cell biology to describe the cohort of peroxisomal matrix proteins that are transported into peroxisomes via the cytosolic receptor Pex5. Most Pex5-dependent cargo proteins carry a C-terminal peroxisomal targeting signal type 1 (PTS1), a tripeptide motif such as SKL or its variants. The designation emphasizes cargo specificity of the Pex5-dependent import pathway across eukaryotes.

Functionally, Pex5 binds cargo in the cytosol and guides it to the peroxisomal membrane, where the Pex5–cargo complex interacts with docking components like Pex14 and Pex13. The cargo is released into the peroxisomal matrix, and Pex5 is recycled back to the cytosol via the Pex1/Pex6 ATPase complex (with other factors). While PTS1-bearing cargo dominates the Pex5 pathway, PTS2-bearing proteins are primarily imported via the Pex7 receptor, and thus are not typically counted among Pex5cargo.

Across fungi, plants, and animals, the Pex5cargo repertoire is diverse and essential for peroxisomal metabolism, including enzymes such as catalase and various beta-oxidation enzymes. Proper sorting of these proteins is critical for peroxisome biogenesis and function; defects in Pex5-mediated import can contribute to peroxisomal biogenesis disorders and related pathologies.

Research on Pex5cargo uses biochemical binding assays, fluorescent tagging, and proteomic approaches to catalog cargo and map targeting signals. Model organisms such as Saccharomyces cerevisiae and mammalian cell lines are used to study the dynamics of Pex5 cargo recognition, import, and recycling, informing our understanding of peroxisome biology and related diseases.