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X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050
Published on: May 13, 2020
Pex5p imports folded tetrameric catalase by interaction with Pex13p
1Department of Biology, Faculty of Sciences, Graduate School of Systems Life Sciences, Kyushu University, Fukuoka, 812-8581, Japan.
Human catalase, a peroxisomal enzyme, is imported into cells via its PTS1-like KANL sequence and Pex5p receptor. The Pex5p-Pex13p interaction is crucial for importing folded, oligomeric proteins like catalase.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Human catalase is a tetrameric enzyme (240 kDa) that degrades hydrogen peroxide (H2O2) within peroxisomes.
- Peroxisomal targeting is mediated by a peroxisomal targeting signal type 1 (PTS1)-like KANL sequence on catalase interacting with the cytosolic PTS1 receptor, Pex5p.
Purpose of the Study:
- To investigate the mechanism of human catalase import into peroxisomes.
- To determine the role of the Pex5p-Pex13p interaction in the import of folded and oligomeric proteins.
Main Methods:
- Expression of human catalase and its mutants in cells.
- Utilizing a Pex5p mutant (Pex5p(Mut234)) defective in Pex13p binding.
- Import assays using catalase mutants, monomeric catalase, and chloramphenicol acetyltransferase (CAT) trimers.
Main Results:
- Human catalase tetramers form in the cytoplasm; PTS expression on each subunit is not required for import.
- Catalase import is impaired in Pex5p(Mut234)-expressing cells, irrespective of its PTS1 sequence.
- Monomeric catalase mutants and trimeric CAT-SKL are imported differently depending on the Pex5p status, highlighting the role of protein folding and oligomerization.
Conclusions:
- The Pex5p-Pex13p interaction is essential for the peroxisomal import of folded and oligomeric proteins.
- Catalase import mechanism differs from typical PTS1 proteins, emphasizing the importance of protein quaternary structure in import.
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