title: Determinants for Arabidopsis peptide transporter targeting to the tonoplast or plasma membrane.
abstract: Di- and tripeptide transporters of the PTR/NRT1 (peptide transporter/nitrate transporter1)-family are localized either at the tonoplast (TP) or plasma membrane (PM). As limited information is available on structural determinants required for targeting of plant membrane proteins, we performed gene shuffling and domain swapping experiments of Arabidopsis PTRs. A 7 amino acid fragment of the hydrophilic N-terminal region of PTR2, PTR4 and PTR6 was required for TP localization and sufficient to redirect not only PM-localized PTR1 or PTR5, but also sucrose transporter SUC2 to the TP. Alanine scanning mutagenesis identified L(11) and I(12) of PTR2 to be essential for TP targeting, while only one acidic amino acid at position 5, 6 or 7 was required, revealing a dileucine (LL or LI) motif with at least one upstream acidic residue. Similar dileucine motifs could be identified in other plant TP transporters, indicating a broader role of this targeting motif in plants. Targeting to the PM required the loop between transmembrane domain 6 and 7 of PTR1 or PTR5. Deletion of either PM or TP targeting signals resulted in retention in internal membranes, indicating that PTR trafficking to these destination membranes requires distinct signals and is in both cases not by default.
authors.affiliation: Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013, Bern, Switzerland.
authors.forename: Nataliya Y
authors.initials: NY
authors.lastname: Komarova
authors.forename: Stefan
authors.initials: S
authors.lastname: Meier
authors.forename: Anna
authors.initials: A
authors.lastname: Meier
authors.forename: Marianne Suter
authors.initials: MS
authors.lastname: Grotemeyer
authors.forename: Doris
authors.initials: D
authors.lastname: Rentsch
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D021382:Protein Sorting Signals; D021381:Protein Transport / Q000235:genetics; D011523:Protoplasts / Q000166:cytology / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics; D014026:Nicotiana / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D026901:Membrane Transport Proteins; C098241:PTR2 protein, Arabidopsis; C510826:PTR3 protein, Arabidopsis; D010940:Plant Proteins; D021382:Protein Sorting Signals; C495664:Ptr1 protein, Arabidopsis; D011993:Recombinant Fusion Proteins; C078729:sucrose transport protein, plant