PTS2containing

PTS2-containing refers to proteins that carry a peroxisomal targeting signal type 2 (PTS2) at their N-terminus, directing them to peroxisomes. Peroxisomes are eukaryotic organelles involved in fatty acid beta-oxidation and various metabolic pathways. Proteins with a PTS2 signal are imported into the peroxisomal matrix for proper function.

The PTS2 motif is a nonapeptide located near the N-terminus, with a commonly cited consensus sequence of RLx5HL. In this motif, the essential residues typically include an arginine followed by a leucine early in the sequence, with a conserved histidine and leucine near the C-terminus of the nonapeptide. In practice, there is variation around the core motif, and not all PTS2 signals conform exactly to the canonical pattern. The presence of a functional PTS2 signal is often predicted bioinformatically but requires experimental validation in many cases.

Import of PTS2-containing proteins relies on the cytosolic receptor Pex7, which recognizes the PTS2 motif. In yeast and some organisms, co-receptors such as Pex18 or Pex21 assist in docking and translocation of the cargo across the peroxisomal membrane. The import pathway generally delivers folded or oligomeric proteins into the matrix, contrasting with some other organelle import systems. PTS2 import can be independent of the PTS1 pathway, though cross-talk and coordination between pathways can occur.

In organisms ranging from yeast to plants and mammals, many peroxisomal matrix enzymes are reported to utilize PTS2 signals. The exact repertoire of PTS2-containing proteins varies by species, and the signals can be degenerate. Disruptions in PTS2 targeting can affect peroxisome biogenesis and metabolism, underscoring the pathway’s biological importance.