PTS1containing

PTS1-containing refers to proteins that bear a peroxisomal targeting signal type 1 (PTS1) at their C-terminus, directing them to peroxisomes where they are imported into the matrix. The canonical PTS1 motif is a C-terminal tripeptide, commonly SKL (serine-lysine-leucine), but many functional variants exist. The broader PTS1 consensus is often described as a [S/A/C]-[R/K]-[L/M] pattern, with SKL and SRL among the most efficient signals. Noncanonical PTS1 sequences also target peroxisomes, though with varying efficiency.

PTS1-containing proteins are recognized by the cytosolic receptor Pex5, which binds the PTS1 motif and delivers the cargo to the peroxisomal membrane. The Pex5–cargo complex interacts with docking factors such as Pex14, enabling translocation of the unfolded or flexible cargo into the peroxisome matrix. Import can accommodate fully folded and oligomeric proteins, a notable feature of peroxisomal import. After delivery, Pex5 is recycled to the cytosol for further rounds of import.

Functions of PTS1-containing proteins are diverse and largely tied to peroxisomal roles, including fatty acid beta-oxidation, plasmalogen synthesis, and detoxification of reactive oxygen species, notably catalase. Examples of PTS1-containing enzymes include catalase and various peroxisomal oxidases and hydroxylases found across eukaryotes.

Clinical relevance arises when PTS1 signals or Pex5-mediated import become defective, potentially contributing to peroxisomal biogenesis disorders. These conditions can disrupt peroxisome function and lead to metabolic disturbances.