Peroxisomal Biogenesis Factor 13 (PEX13)

PEX13 functions as a docking factor for the predominantly cytoplasmic PTS1 receptor. PTS1 consists of a C-terminal tripeptide with the sequence ser-lys-leu or a conservative variant and is used by almost all proteins destined for the peroxisomal lumen. PTS2, also directs proteins to the peroxisomal lumen but differs from PTS1 because it is found at the N terminus and is used much less commonly. Integral peroxisomal membrane proteins use neither PTS1 nor PTS2, but rather a distinct type of signal. Pex13p SH3 interacted specifically with Pex5p in vitro. Pex5p was present mainly in the cytosol and only a small fraction was associated with peroxisomes. Pex13p is a component of the peroxisomal protein import machinery onto which the mobile pex5p receptor docks for the delivery of the selected PTS1 protein.