Nucleotide-dependent assembly of the peroxisomal receptor export complex

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Peroxisome biogenesis is crucial for cellular function.
• AAA-ATPases Pex1p and Pex6p form a complex essential for peroxisome formation.
• This complex recycles the import receptor Pex5p after matrix protein import.

Purpose of the Study:

• To investigate the recruitment mechanism of the Pex1/6p AAA-complex to the peroxisomal membrane.
• To elucidate the interaction between the AAA-complex and its anchor protein Pex15p.
• To understand the role of nucleotide binding and hydrolysis in this process.

Main Methods:

• In vivo and in vitro binding assays.
• Analysis of AAA-complex assembly and stoichiometry.
• Biochemical characterization of protein interactions.

Main Results:

• The Pex1/6p AAA-complex is assembled and binds Pex15p efficiently, even under ADP conditions.
• Pex6p directly mediates the binding to the cytosolic part of Pex15p.
• The stoichiometry of the complex is Pex1p/Pex6p/Pex15p (3:3:3), with each Pex6p molecule binding Pex15p.
• Binding is stabilized by ATP binding to Pex6p's second AAA-domain, preventing hydrolysis.

Conclusions:

• Receptor release during peroxisomal protein import involves a nucleotide-dependent cycle of Pex1/6p binding and release from Pex15p.
• The AAA-complex's interaction with Pex15p is a key regulatory step in peroxisome function.