Journal
TRAFFIC
Volume 13, Issue 10, Pages 1364-1377Publisher
WILEY-BLACKWELL
DOI: 10.1111/j.1600-0854.2012.01391.x
Keywords
import of folded and oligomeric protein; peroxin; peroxisomal matrix protein import; peroxisome biogenesis; Pex5p; PTS1 receptor
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Funding
- CREST grant from the Science and Technology Agency of Japan
- Ministry of Education, Culture, Sports, Science, and Technology of Japan
- Takeda Science Foundation
- Japan Foundation for Applied Enzymology
- Grants-in-Aid for Scientific Research [23770231] Funding Source: KAKEN
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Human catalase forms a 240-kDa tetrameric complex and degrades H2O2 in peroxisomes. Human catalase is targeted to peroxisomes by the interaction of its peroxisomal targeting signal type 1 (PTS1)-like KANL sequence with the cytosolic PTS1 receptor Pex5p. We show herein that human catalase tetramers are formed in the cytoplasm and that the expression of a PTS signal on each of the four subunits is not necessary for peroxisomal transport. We previously demonstrated that a Pex5p mutant defective in binding to Pex13p, designated Pex5p(Mut234), imports typical PTS1-type proteins but not catalase. This impaired catalase import is not rescued by replacing its C-terminal KANL sequence with a typical PTS1 sequence, SKL, indicating that the failure of catalase import in Mut234-expressing cells is not due to its weak PTS1. In contrast, several enzymatically inactive and monomeric mutants of catalase are efficiently imported in Mut234-expressing cells. Moreover, trimeric chloramphenicol acetyltransferase (CAT) harboring SKL is not imported in Pex5p(Mut234)-expressing cells, but CAT-SKL trimers are transported to peroxisomes in the wild-type cells. These findings suggest that the Pex5pPex13p interaction likely plays a pivotal role in the peroxisomal import of folded and oligomeric proteins.
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