title: Multiple organelle-targeting signals in the N-terminal portion of peroxisomal membrane protein PMP70.
abstract: Most membrane proteins are recognized by a signal recognition particle and are cotranslationally targeted to the endoplasmic reticulum (ER) membrane, whereas almost all peroxisomal membrane proteins are posttranslationally targeted to the destination. Here we examined organelle-targeting properties of the N-terminal portions of the peroxisomal isoform of the ABC transporter PMP70 (ABCD3) using enhanced green fluorescent protein (EGFP) fusion. When the N-terminal 80 amino acid residue (N80)-segment preceding transmembrane segment (TM) 1 was deleted and the TM1-TM2 region was fused to EGFP, the TM1 segment induced ER-targeting and integration in COS cells. When the N80-segment was fused to EGFP, the fusion protein was targeted to the outer mitochondrial membrane. When both the N80-segment and the following TM1-TM2 region were present, the fusion located exclusively to the peroxisome. The full-length PMP70 molecule was clearly located in the ER in the absence of the N80-segment, even when multiple peroxisome-targeting signals were retained. We concluded that the TM1 segment possesses a sufficient ER-targeting function and that the N80-segment is critical for suppressing the ER-targeting function to allow the TM1-TM2 region to localize to the peroxisome. Cooperation of the organelle-targeting signals enables PMP70 to correctly target to peroxisomal membranes.
authors.affiliation: Graduate School of Life Science, University of Hyogo, Kouto Ako-gun, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Iwashita
authors.forename: Masashi
authors.initials: M
authors.lastname: Tsuchida
authors.forename: Miwa
authors.initials: M
authors.lastname: Tsukuda
authors.forename: Yukari
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Emi
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Kida
authors.forename: Masayuki
authors.initials: M
authors.lastname: Komori
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kashiwayama
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Imanaka
authors.forename: Masao
authors.initials: M
authors.lastname: Sakaguchi
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006031:Glycosylation / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007425:Intracellular Membranes / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D051336:Mitochondrial Membranes / Q000378:metabolism; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020675:Peroxisomes / Q000378:metabolism*; D061988:Proteasome Inhibitors; D054730:Protein Interaction Domains and Motifs / Q000235:genetics / Q000502:physiology; D021382:Protein Sorting Signals / Q000235:genetics / Q000502:physiology*; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: C063305:ABCD3 protein, human; D018528:ATP-Binding Cassette Transporters; C489271:Abcd3 protein, mouse; D050505:Mutant Proteins; D061988:Proteasome Inhibitors; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins