Figure 3

Peroxisomal protein import. Pex5 and Pex7 recognize proteins with PTS1 and PTS2, respectively. Pex18 and Pex21 act as co-receptors for Pex7. The receptor-cargo complex is recognized by Pex13, Pex14 and Pex17. Pex5 shuttles between cytosol and membrane (and may be lumen, which at state is controversially discussed), and mediates the transfer of the cargo protein and becomes subsequently monoubiquitinated by Pex22-anchored Pex12 and Pex4. Pex5 is exported by Pex1 and Pex6 (anchored by Pex15). Malfunction of Pex5 recycling induces the RADAR mechanism, by which Pex5 becomes polyubiqunated via the E2-conjugating enzyme Ubc4 or Ubc5 and the E3-ubiquitin ligase Pex2 and Pex10. The polyubiquitinylated Pex5 is exported and degraded in the cytosol. (b) Type-II PMPs interact with Pex19, which docks to Pex3 and releases the PMP into the membrane. For color code see legend of Figure 2.