Solution structure of human Pex5.Pex14.PTS1 protein complexes obtained by small angle X-ray scattering

Area of Science:

• Cell Biology
• Molecular Biology
• Structural Biology

Background:

• Peroxisomal matrix proteins require targeting signals for import.
• The Pex5p receptor facilitates the import of proteins with C-terminal peroxisomal targeting signals.
• The precise mechanism of cargo-loaded Pex5p docking to the peroxisome remains elusive due to a lack of structural data.

Purpose of the Study:

• To elucidate the structural basis of the Pex5p-Pex14p interaction.
• To understand the docking mechanism of peroxisomal import machinery.
• To investigate the solution structure of the Pex5p-Pex14p complex.

Main Methods:

• Small-angle X-ray scattering (SAXS).
• Static light scattering (SLS).
• Stoichiometry titration studies.

Main Results:

• The Pex5p.Pex14p complex exhibits a 1:6 stoichiometry.
• Low-resolution structural models of the complex were generated using SAXS data.
• Free human Pex5p is monomeric and elongated, with a partially unfolded N-terminal domain.
• The N terminus of Pex5p remains extended in the complex, intermingling with Pex14p.

Conclusions:

• The extended structure of Pex5p is crucial for its interactions within the peroxisomal docking complex.
• This structural feature may facilitate interactions with lipids and membrane proteins.
• Understanding this complex is key to deciphering peroxisomal protein translocation.