title: Identification and characterization of a novel plastidic adenine nucleotide uniporter from Solanum tuberosum.
abstract: Homologs of BT1 (the Brittle1 protein) are found to be phylogenetically related to the mitochondrial carrier family and appear to occur in both mono- and dicotyledonous plants. Whereas BT1 from cereals is probably involved in the transport of ADP-glucose, which is essential for starch metabolism in endosperm plastids, BT1 from a noncereal plant, Solanum tuberosum (StBT1), catalyzes an adenine nucleotide uniport when functionally integrated into the bacterial cytoplasmic membrane. Import studies into intact Escherichia coli cells harboring StBT1 revealed a narrow substrate spectrum with similar affinities for AMP, ADP, and ATP of about 300-400 mum. Transiently expressed StBT1-green fluorescent protein fusion protein in tobacco leaf protoplasts showed a plastidic localization of the StBT1. In vitro synthesized radioactively labeled StBT1 was targeted to the envelope membranes of isolated spinach chloroplasts. Furthermore, we showed by real time reverse transcription-PCR a ubiquitous expression pattern of the StBT1 in autotrophic and heterotrophic potato tissues. We therefore propose that StBT1 is a plastidic adenine nucleotide uniporter used to provide the cytosol and other compartments with adenine nucleotides exclusively synthesized inside plastids.
authors.affiliation: Pflanzenphysiologie, Technische Universität Kaiserslautern, Erwin-Schroedinger-Strasse 22, D-67663 Kaiserslautern, Germany.
authors.forename: Michaela
authors.initials: M
authors.lastname: Leroch
authors.forename: Simon
authors.initials: S
authors.lastname: Kirchberger
authors.forename: Ilka
authors.initials: I
authors.lastname: Haferkamp
authors.forename: Markus
authors.initials: M
authors.lastname: Wahl
authors.forename: H Ekkehard
authors.initials: HE
authors.lastname: Neuhaus
authors.forename: Joachim
authors.initials: J
authors.lastname: Tjaden
mesh_terms: D000227:Adenine Nucleotides / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D002736:Chloroplasts / Q000737:chemistry* / Q000201:enzymology / Q000378:metabolism*; D051599:Glucose-1-Phosphate Adenylyltransferase; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D033704:Nucleotide Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011198:Solanum tuberosum / Q000235:genetics / Q000378:metabolism*
chemical_list: D000227:Adenine Nucleotides; D033704:Nucleotide Transport Proteins; D010940:Plant Proteins; D049452:Green Fluorescent Proteins; D009713:Nucleotidyltransferases; D051599:Glucose-1-Phosphate Adenylyltransferase