The AAA-type ATPases Pex1p and Pex6p and their role in peroxisomal matrix protein import in Saccharomyces cerevisiae

Grimm, Immanuel; Saffian, Delia; Platta, Harald W.; Erdmann, Ralf

doi:10.1016/j.bbamcr.2011.09.005

Cited by 33 publications

(27 citation statements)

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“…Both proteins are predicted to contain two ATPase domains (D1 and D2; Fig. 1A) and are known to associate with one another (27,28). Pex1 and Pex6 are peroxisome-associated proteins that are conserved in all eukaryotic cells.…”

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confidence: 99%

Unique double-ring structure of the peroxisomal Pex1/Pex6 ATPase complex revealed by cryo-electron microscopy

Blok

Tan

Wang

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Members of the AAA family of ATPases assemble into hexameric double rings and perform vital functions, yet their molecular mechanisms remain poorly understood. Here, we report structures of the Pex1/Pex6 complex; mutations in these proteins frequently cause peroxisomal diseases. The structures were determined in the presence of different nucleotides by cryo-electron microscopy. Models were generated using a computational approach that combines Monte Carlo placement of structurally homologous domains into density maps with energy minimization and refinement protocols. Pex1 and Pex6 alternate in an unprecedented hexameric double ring. Each protein has two N-terminal domains, N1 and N2, structurally related to the single N domains in p97 and N-ethylmaleimide sensitive factor (NSF); N1 of Pex1 is mobile, but the others are packed against the double ring. The N-terminal ATPase domains are inactive, forming a symmetric D1 ring, whereas the C-terminal domains are active, likely in different nucleotide states, and form an asymmetric D2 ring. These results suggest how subunit activity is coordinated and indicate striking similarities between Pex1/Pex6 and p97, supporting the hypothesis that the Pex1/Pex6 complex has a role in peroxisomal protein import analogous to p97 in ER-associated protein degradation.Pex1 | Pex6 | AAA ATPase | cryo-electron microscopy | peroxisome T he AAA (ATPases associated with diverse cellular activities) family of ATPases contains a large number of proteins that perform important functions in cells (1). Many members of this family form hexamers. These hexamers consist either of a single ring of ATPase domains or of stacked rings formed by tandem ATPase domains in a single polypeptide chain (type I and II ATPases, respectively). Both classes of AAA ATPases often use the energy of ATP hydrolysis to move macromolecules. Examples of single-ring ATPases include the F1 ATPase (2), which rotates a polypeptide inside its central pore, ClpX (3), which moves polypeptides into the proteolytic chamber of ClpP, and the helicase gp4 of T7 phage (4), which pulls a DNA strand through its center. Double-ring ATPases generally act on polypeptides. Prominent members of this family include N-ethylmaleimide sensitive factor (NSF), p97/VCP (valosin-containing protein), and Hsp104 in eukaryotes and ClpB in bacteria (5-7). NSF dissociates SNARE complexes generated during membrane fusion, p97/VCP plays a role in many processes, including ERassociated protein degradation (ERAD), and Hsp104 and ClpB disassemble protein aggregates.The molecular mechanism of many hexameric AAA ATPases is only poorly understood, particularly for those that move polypeptide chains. In addition, the mechanism appears to differ among the known examples. For the F1 ATPase, it has been established that ATPase domains hydrolyze ATP continuously in a strictly consecutive manner around the ring (2). In contrast, in another single-ring ATPase, ClpX, several ATPase domains hydrolyze ATP in sporadic bursts, either simultaneously or in short succession...

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confidence: 99%

Unique double-ring structure of the peroxisomal Pex1/Pex6 ATPase complex revealed by cryo-electron microscopy

Blok

Tan

Wang

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…1A). In yeast (Saccharomyces cerevisiae), membrane-associated PEX5 is ubiquitinated, recognized by a complex of ATP-hydrolyzing enzymes comprised of PEX1 and PEX6, and retrotranslocated out of the peroxisome to be used in additional rounds of import (for review, see Fujiki et al, 2012;Grimm et al, 2012).…”

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Peroxisomal Ubiquitin-Protein Ligases Peroxin2 and Peroxin10 Have Distinct But Synergistic Roles in Matrix Protein Import and Peroxin5 Retrotranslocation in Arabidopsis

2014

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Peroxisomal matrix proteins carry peroxisomal targeting signals (PTSs), PTS1 or PTS2, and are imported into the organelle with the assistance of peroxin (PEX) proteins. From a microscopy-based screen to identify Arabidopsis (Arabidopsis thaliana) mutants defective in matrix protein degradation, we isolated unique mutations in PEX2 and PEX10, which encode ubiquitin-protein ligases anchored in the peroxisomal membrane. In yeast (Saccharomyces cerevisiae), PEX2, PEX10, and a third ligase, PEX12, ubiquitinate a peroxisome matrix protein receptor, PEX5, allowing the PEX1 and PEX6 ATP-hydrolyzing enzymes to retrotranslocate PEX5 out of the membrane after cargo delivery. We found that the pex2-1 and pex10-2 Arabidopsis mutants exhibited defects in peroxisomal physiology and matrix protein import. Moreover, the pex2-1 pex10-2 double mutant exhibited severely impaired growth and synergistic physiological defects, suggesting that PEX2 and PEX10 function cooperatively in the wild type. The pex2-1 lesion restored the unusually low PEX5 levels in the pex6-1 mutant, implicating PEX2 in PEX5 degradation when retrotranslocation is impaired. PEX5 overexpression altered pex10-2 but not pex2-1 defects, suggesting that PEX10 facilitates PEX5 retrotranslocation from the peroxisomal membrane. Although the pex2-1 pex10-2 double mutant displayed severe import defects of both PTS1 and PTS2 proteins into peroxisomes, both pex2-1 and pex10-2 single mutants exhibited clear import defects of PTS1 proteins but apparently normal PTS2 import. A similar PTS1-specific pattern was observed in the pex4-1 ubiquitin-conjugating enzyme mutant. Our results indicate that Arabidopsis PEX2 and PEX10 cooperate to support import of matrix proteins into plant peroxisomes and suggest that some PTS2 import can still occur when PEX5 retrotranslocation is slowed.

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“…During ubiquitination, ubiquitin-conjugating enzymes (UBCs) assist ubiquitinprotein ligases in covalently attaching ubiquitin to substrate proteins. S. cerevisiae PEX5 monoubiquitination by the peroxisome-tethered UBC PEX4 and the peroxisomal ubiquitin-protein ligase PEX12 (Platta et al, 2009) allows a peroxisome-tethered ATPase complex to recycle PEX5 to the cytosol for further rounds of cargo recruitment (for review, see Grimm et al, 2012). In contrast, PEX5 polyubiquitination by the cytosolic UBC4 acting with the peroxisomal ubiquitin-protein ligase PEX2 targets PEX5 for proteasomal degradation (Platta et al, 2009).…”

Section: Roles For Ubiquitination In Receptor Recycling and Peroxin Dmentioning

confidence: 99%

Peroxisome Function, Biogenesis, and Dynamics in Plants

2017

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The AAA-type ATPases Pex1p and Pex6p and their role in peroxisomal matrix protein import in Saccharomyces cerevisiae

Cited by 33 publications

References 144 publications

Unique double-ring structure of the peroxisomal Pex1/Pex6 ATPase complex revealed by cryo-electron microscopy

Unique double-ring structure of the peroxisomal Pex1/Pex6 ATPase complex revealed by cryo-electron microscopy

Peroxisomal Ubiquitin-Protein Ligases Peroxin2 and Peroxin10 Have Distinct But Synergistic Roles in Matrix Protein Import and Peroxin5 Retrotranslocation in Arabidopsis

Peroxisome Function, Biogenesis, and Dynamics in Plants

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