PEX20

PEX20, or peroxin 20, is a protein found in a variety of fungi that functions as a peroxisome biogenesis factor. It is specifically linked to the import of matrix proteins that carry the peroxisomal targeting signal type 2 (PTS2).

In organisms where PEX20 is present, the protein often acts as an adaptor or co-receptor for the Pex7 receptor, aiding in the recruitment of PTS2-containing cargo to the peroxisomal membrane. This process typically involves cooperation with membrane docking components such as Pex13 and Pex14, enabling translocation of PTS2 proteins into the peroxisome. PEX20 is generally cytosolic but can associate with peroxisomes when import is active. The role of PEX20 can be essential for proper peroxisome biogenesis; loss of the gene disrupts PTS2 import and can lead to abnormal or absent peroxisomes in the affected cells.

Evolutionarily, PEX20 is functionally related to other PTS2 cofactors found in fungi, such as Pex18 and Pex21 in certain yeasts, where these cofactors modulate Pex7 activity. The presence and sequence of PEX20 vary among species, reflecting divergent strategies for handling PTS2 import.

In research, PEX20 helps illuminate the mechanisms of peroxisomal matrix protein import and the broader process of peroxisome assembly. It is not widely reported as a canonical peroxin in higher eukaryotes, where alternate cofactors fulfill the PTS2 import role.