title: Pex5p imports folded tetrameric catalase by interaction with Pex13p.
abstract: Human catalase forms a 240-kDa tetrameric complex and degrades H(2) O(2) 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 Pex5p-Pex13p interaction likely plays a pivotal role in the peroxisomal import of folded and oligomeric proteins.
authors: Department of Biology, Faculty of Sciences, Graduate School of Systems Life Sciences, Kyushu University, Fukuoka, 812-8581, Japan.
authors: Hidenori
authors: H
authors: Otera
authors: Yukio
authors: Y
authors: Fujiki
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D016466:CHO Cells; D002374:Catalase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D009154:Mutation; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000378:metabolism*; D017510:Protein Folding; D021382:Protein Sorting Signals; D020836:Protein Structure, Quaternary; D021381:Protein Transport; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D000074435:Peroxisome-Targeting Signal 1 Receptor; D021382:Protein Sorting Signals; D018160:Receptors, Cytoplasmic and Nuclear; D002374:Catalase; D015500:Chloramphenicol O-Acetyltransferase