Towards the molecular architecture of the peroxisomal receptor docking complex

Abstract

Import of yeast peroxisomal matrix proteins is initiated by cytosolic receptors, which specifically recognize and bind the respective cargo proteins. At the peroxisomal membrane, the cargo-loaded receptor interacts with the docking protein Pex14p that is tightly associated with Pex17p. Previous data suggest that this interaction triggers the formation of an import pore for further translocation of the cargo. The mechanistic principles, however, are unclear, mainly because structures of higher-order assemblies are still lacking. Here, using an integrative approach, we provide the structural characterization of the major components of the peroxisomal docking complex Pex14p/Pex17p, in a native bilayer environment, and reveal its subunit organization. Our data show that three copies of Pex14p and a single copy of Pex17p assemble to form a 20-nm rod-like particle. The different subunits are arranged in a parallel manner, showing interactions along their complete sequences and providing receptor binding sites on both membrane sides. The long rod facing the cytosol is mainly formed by the predicted coiled-coil domains of Pex14p and Pex17p, possibly providing the necessary structural support for the formation of the import pore. Further implications of Pex14p/Pex17p for formation of the peroxisomal translocon are discussed.

Comparative Genomics of Peroxisome Biogenesis Proteins: Making Sense of the PEX Proteins

“…PEX17 is characterized by a single transmembrane helix at the N-terminal. As described above, S. cerevisiae PEX14 and PEX17 together form a rod-like structure at the peroxisomal membrane ( Lill et al, 2020 ). PEX33 is a paralog of PEX14, whereas PEX17 is a protein partially aligning to the C-terminal of PEX14 and PEX33, suggesting PEX17 is a PEX14-like protein.…”

“…In addition, only in Opisthokonta organisms (Fungi and Metazoa) and amoebozoa, PEX13 has a predicted SH3 domain at the C-terminal ( Supplementary Figure 1A ), which likely controls its interaction with other proteins. PEX14 also contains a predicted transmembrane helix, but seems to be largely structurally disordered ( Supplementary Figure 1B ), although it also includes several coiled-coil domains (e.g., Lill et al, 2020 ). In vitro protease protection experiments using human PEX13 and PEX14 confirmed that both proteins are integral membrane proteins.…”

“…Human PEX14 has an N in –C out topology, while PEX13 adopts an N out –C in topology, thereby exposing its SH3 domain to the peroxisomal matrix ( Barros-Barbosa et al, 2019a ). The architecture of the S. cerevisiae PEX14-PEX17 complex was recently elucidated and revealed that PEX14 forms a 3:1 heterotetrameric complex with PEX17, forming a rod-like structure of approximately 20 nm that is exposed to the cytosol ( Lill et al, 2020 ). This structure is mainly formed by the coiled-coil domains of PEX14 and PEX17.…”

“…This structure is mainly formed by the coiled-coil domains of PEX14 and PEX17. Besides its coiled-coil domains, PEX14 has a predicted intrinsically disordered C-terminal domain, which may be involved in recruiting import receptor PEX5 ( Lill et al, 2020 ).…”

Current advances in the function and biogenesis of peroxisomes and their roles in health and disease

“…The first talk was given by Pascal Lill (Christos Gatsogiannis Laboratory, Max Planck Institute of Molecular Physiology, Dortmund, Germany), who presented a structural characterization of the main components of the peroxisomal docking complex in S. cerevisiae, Pex14 and Pex17. Pascal and his colleagues applied cryo-electron microscopy single particle analysis and cryo-electron tomography on purified complexes and found that three copies of Pex14p and a single copy of Pex17p assemble to form a 20 nm rod-like particle (Lill et al 2020). The different subunits are arranged in a parallel manner, showing interactions along their complete sequences and providing receptor-binding sites on both membrane sides.…”