title: The cytosolic domain of PEX3, a protein involved in the biogenesis of peroxisomes, binds membrane lipids.
abstract: According to current models, most newly synthesized peroxisomal intrinsic membrane proteins are recognized in the cytosol and targeted to the peroxisomal membrane by PEX19. At the organelle membrane the PEX19-cargo protein complex interacts with PEX3, a protein believed to possess only one transmembrane domain and exposing the majority of its polypeptide chain into the cytosol. In agreement with this topological model, a recombinant protein comprising the cytosolic domain of PEX3 can be purified in a soluble and monomeric form in the absence of detergents or other solubilizing agents. Here, we show that this recombinant protein actually precipitates when incubated with mild detergents, suggesting that this domain of PEX3 interacts with amphipathic molecules. Following this observation, we tested this recombinant protein in lipid-binding assays and found that it interacts strongly with liposomes inducing their flocculation or even partial solubilization. The implications of these findings are discussed.
authors.affiliation: Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, 4150-180 Porto, Portugal.
authors.forename: Manuel P
authors.initials: MP
authors.lastname: Pinto
authors.forename: Cláudia P
authors.initials: CP
authors.lastname: Grou
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: D001692:Biological Transport / Q000502:physiology; D006801:Humans; D008074:Lipoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008563:Membrane Lipids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D000074401:Peroxins; D020675:Peroxisomes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D008074:Lipoproteins; D008563:Membrane Lipids; D008565:Membrane Proteins; D000074401:Peroxins; C113138:Pex3 protein, human; D011994:Recombinant Proteins; C087343:PEX19 protein, human