The peroxisomal AAA-ATPase Pex1/Pex6 unfolds substrates by processive threading

• Published in: Nature communications Vol. 9; no. 1; pp. 135 - 15
• Main Authors: Gardner, Brooke M., Castanzo, Dominic T., Chowdhury, Saikat, Stjepanovic, Goran, Stefely, Matthew S., Hurley, James H., Lander, Gabriel C., Martin, Andreas
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10.01.2018; Nature Publishing Group; Nature Portfolio
• Subjects: 101/28; 101/58; 60 APPLIED LIFE SCIENCES; 631/45/173; 631/535/1258; 631/535/1266; 631/80/304; 631/80/642/2013; 82/80; 82/83; Adenosine triphosphatase; Adenosine Triphosphatases - antagonists & inhibitors; ATPases Associated with Diverse Cellular Activities - metabolism; BASIC BIOLOGICAL SCIENCES; Biosynthesis; electron microscopy; enzyme mechanisms; Evolution; Humanities and Social Sciences; Imports; Machinery and equipment; mechanisms of disease; Membrane proteins; Membrane Proteins - metabolism; multidisciplinary; Mutation; peroxisomes; Peroxisomes - enzymology; Phosphoproteins - metabolism; Protein Conformation; Protein transport; Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins - metabolism; Science; science & technology - other topics; Science (multidisciplinary); Substrates; Translocase; x-ray crystallography
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-017-02474-4

Pex1 and Pex6 form a heterohexameric motor essential for peroxisome biogenesis and function, and mutations in these AAA-ATPases cause most peroxisome-biogenesis disorders in humans. The tail-anchored protein Pex15 recruits Pex1/Pex6 to the peroxisomal membrane, where it performs an unknown function required for matrix-protein import. Here we determine that Pex1/Pex6 from S . cerevisiae is a protein translocase that unfolds Pex15 in a pore-loop-dependent and ATP-hydrolysis-dependent manner. Our structural studies of Pex15 in isolation and in complex with Pex1/Pex6 illustrate that Pex15 binds the N-terminal domains of Pex6, before its C-terminal disordered region engages with the pore loops of the motor, which then processively threads Pex15 through the central pore. Furthermore, Pex15 directly binds the cargo receptor Pex5, linking Pex1/Pex6 to other components of the peroxisomal import machinery. Our results thus support a role of Pex1/Pex6 in mechanical unfolding of peroxins or their extraction from the peroxisomal membrane during matrix-protein import. Pex1 and Pex6 form a heterohexameric Type-2 AAA-ATPase motor whose function in peroxisomal matrix-protein import is still debated. Here, the authors combine structural, biochemical, and cell-biological approaches to show that Pex1/Pex6 is a protein unfoldase, which supports a role in mechanical unfolding of peroxin proteins.