PMID: 24235149

Authors:

Neuhaus A, Kooshapur H, Wolf J, Meyer HN, Madl T, Saidowsky J, Hambruch E, Lassam A, Jung M, Sattler M, Schliebs W, Erdmann R

Title:

A novel Pex14 interacting site of human Pex5 is critical for matrix protein import into peroxisomes.

Journal:

J Biol Chem. 2013 Nov 14.

Abstract:

Protein import into peroxisomes relies on the import receptor Pex5, which recognizes proteins with a peroxisomal targeting signal 1 (PTS1) in the cytosol and directs them to a docking complex at the peroxisomal membrane. Receptor-cargo docking occurs at the membrane-associated protein Pex14. In human cells, this interaction is mediated by seven conserved diaromatic pentapeptide motifs (WxxxF/Y-motifs) in the N-terminal half of Pex5 and the N-terminal domain (NTD) of Pex14. A systematic screening of a Pex5-peptide library by ligand blot analysis revealed a novel Pex5-Pex14 interaction site of Pex5. The novel motif comprises the sequence LVAEF with the evolutionary conserved consensus sequence LVxEF. Replacement of the amino acids LVAEF sequence by alanines strongly affects matrix protein import into peroxisomes in vivo. The NMR structure of a complex of Pex5-(57-71) with Pex14-NTD showed that the novel motif binds in a similar alpha-helical orientation as the WxxxF/Y motif but that the tryptophan pocket is now occupied by a leucine residue. Surface plasmon resonance analyses revealed 33-times faster dissociation rates for the LVxEF ligand when compared to a WxxxF/Y motif. Surprisingly, substitution of the novel motif with the higher affinity WxxxF/Y motif impairs protein import into peroxisomes. These data indicate that the distinct kinetic properties of the novel Pex14-binding site in Pex5 are important for processing of the PTS1 receptor at the peroxisomal membrane. The novel Pex14 binding site may represent the initial tethering site of Pex5 from which the cargo-loaded receptor is further processed in a sequential manner.