High impact information on PEX4

• The Pas2 protein essential for peroxisome biogenesis is related to ubiquitin-conjugating enzymes [1].
• Therefore, Pex22p anchors Pex4p at the peroxisomal membrane [2].
• However, the severe sucrose dependence of the pex4 pex22 mutant is not accompanied by correspondingly strong defects in peroxisomal matrix protein import, suggesting that this peroxin pair may have novel plant targets in addition to those important in fungi [3].
• By screening for reduced response to indole-3-butyric acid, which is metabolized to active auxin in peroxisomes, we isolated an Arabidopsis thaliana peroxin4 (pex4) mutant [3].
• Furthermore, Pex1p and Pex6p were found to act upstream of Pex4p and Pex22p [4].

Biological context of PEX4

• The peroxisome biogenesis factors pex4p, pex22p, pex1p, and pex6p act in the terminal steps of peroxisomal matrix protein import [4].
• These results suggest that Pex1p, Pex4p, Pex6p, and Pex22p act late in peroxisomal matrix protein import, after matrix protein translocation [4].
• Crossing of pas1-1 and pas2 strains resulted in diploid cells that had regained the ability to grow on oleic acid as sole carbon source and to form peroxisomes [5].

Other interactions of PEX4

• We demonstrate the ubiquitination of Pex5p in cells lacking components of the peroxisomal AAA (ATPases associated with various cellular activities) or Pex4p-Pex22p complexes of the peroxisomal protein import machinery and in cells affected in proteasomal degradation [6].

References