title: Revisiting the intraperoxisomal pathway of mammalian PEX7.
abstract: Newly synthesized peroxisomal proteins containing a cleavable type 2 targeting signal (PTS2) are transported to the peroxisome by a cytosolic PEX5-PEX7 complex. There, the trimeric complex becomes inserted into the peroxisomal membrane docking/translocation machinery (DTM), a step that leads to the translocation of the cargo into the organelle matrix. Previous work suggests that PEX5 is retained at the DTM during all the steps occurring at the peroxisome but whether the same applies to PEX7 was unknown. By subjecting different pre-assembled trimeric PEX5-PEX7-PTS2 complexes to in vitro co-import/export assays we found that the export competence of peroxisomal PEX7 is largely determined by the PEX5 molecule that transported it to the peroxisome. This finding suggests that PEX7 is also retained at the DTM during the peroxisomal steps and implies that cargo proteins are released into the organelle matrix by DTM-embedded PEX7. The release step does not depend on PTS2 cleavage. Rather, our data suggest that insertion of the trimeric PEX5-PEX7-PTS2 protein complex into the DTM is probably accompanied by conformational alterations in PEX5 to allow release of the PTS2 protein into the organelle matrix.
authors.affiliation: 1] Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal [2] Organelle Biogenesis and Function Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
authors.forename: Tony A
authors.initials: TA
authors.lastname: Rodrigues
authors.affiliation: 1] Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal [2] Organelle Biogenesis and Function Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
authors.forename: Cláudia P
authors.initials: CP
authors.lastname: Grou
authors.affiliation: 1] Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal [2] Organelle Biogenesis and Function Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal [3] Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal.
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Azevedo
mesh_terms: D000818:Animals; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics; D015388:Organelles / Q000737:chemistry / Q000235:genetics; D000074437:Peroxisomal Targeting Signal 2 Receptor; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000737:chemistry / Q000235:genetics*; D010957:Plasmids / Q000235:genetics; D011487:Protein Conformation; D021381:Protein Transport; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000378:metabolism
chemical_list: D046912:Multiprotein Complexes; C000614264:PEX5 protein, human; C000614269:PEX7 protein, human; D000074437:Peroxisomal Targeting Signal 2 Receptor; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear