title: Ubiquitination of mammalian Pex5p, the peroxisomal import receptor.
abstract: Protein translocation across the peroxisomal membrane requires the concerted action of numerous peroxins. One central component of this machinery is Pex5p, the cycling receptor for matrix proteins. Pex5p recognizes newly synthesized proteins in the cytosol and promotes their translocation across the peroxisomal membrane. After this translocation step, Pex5p is recycled back into the cytosol to start a new protein transport cycle. Here, we show that mammalian Pex5p is ubiquitinated at the peroxisomal membrane. Two different types of ubiquitination were detected, one of which is thiol-sensitive, involves Cys(11) of Pex5p, and is necessary for the export of the receptor back into the cytosol. Together with mechanistic data recently described for yeast Pex5p, these findings provide strong evidence for the existence of Pex4p- and Pex22p-like proteins in mammals.
authors.affiliation: Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
authors.forename: Andreia F
authors.initials: AF
authors.lastname: Carvalho
authors.forename: Manuel P
authors.initials: MP
authors.lastname: Pinto
authors.forename: Cláudia P
authors.initials: CP
authors.lastname: Grou
authors.forename: Inês S
authors.initials: IS
authors.lastname: Alencastre
authors.forename: Marc
authors.initials: M
authors.lastname: Fransen
authors.forename: Clara
authors.initials: C
authors.lastname: Sá-Miranda
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Azevedo
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001345:Autoradiography; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D019286:Endopeptidase K / Q000494:pharmacology; D005982:Glutathione Transferase / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000378:metabolism*; D010957:Plasmids; D011233:Precipitin Tests; D020033:Protein Isoforms; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D000911:Antibodies, Monoclonal; D026901:Membrane Transport Proteins; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020033:Protein Isoforms; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D013438:Sulfhydryl Compounds; D044763:Ubiquitin-Conjugating Enzymes; D005982:Glutathione Transferase; D019286:Endopeptidase K; D003545:Cysteine