title: Identification, expression, and functional analyses of a thylakoid ATP/ADP carrier from Arabidopsis.
abstract: In plants the chloroplast thylakoid membrane is the site of light-dependent photosynthetic reactions coupled to ATP synthesis. The ability of the plant cell to build and alter this membrane system is essential for efficient photosynthesis. A nucleotide translocator homologous to the bovine mitochondrial ADP/ATP carrier (AAC) was previously found in spinach thylakoids. Here we have identified and characterized a thylakoid ATP/ADP carrier (TAAC) from Arabidopsis.(i) Sequence homology with the bovine AAC and the prediction of chloroplast transit peptides indicated a putative carrier encoded by the At5g01500 gene, as a TAAC. (ii) Transiently expressed TAAC-green fluorescent protein fusion construct was targeted to the chloroplast. Western blotting using a peptide-specific antibody together with immunogold electron microscopy revealed a major location of TAAC in the thylakoid membrane. Previous proteomic analyses identified this protein in chloroplast envelope preparations. (iii) Recombinant TAAC protein specifically imports ATP in exchange for ADP across the cytoplasmic membrane of Escherichia coli. Studies on isolated thylakoids from Arabidopsis confirmed these observations. (iv) The lack of TAAC in an Arabidopsis T-DNA insertion mutant caused a 30-40% reduction in the thylakoid ATP transport and metabolism. (v) TAAC is readily expressed in dark-grown Arabidopsis seedlings, and its level remains stable throughout the greening process. Its expression is highest in developing green tissues and in leaves undergoing senescence or abiotic stress. We propose that the TAAC protein supplies ATP for energy-dependent reactions during thylakoid biogenesis and turnover in plants.
authors.affiliation: Division of Cell Biology, Linköping University, SE-581 85 Linköping, Sweden.
authors.forename: Sophie
authors.initials: S
authors.lastname: Thuswaldner
authors.forename: Jens O
authors.initials: JO
authors.lastname: Lagerstedt
authors.forename: Marc
authors.initials: M
authors.lastname: Rojas-Stütz
authors.forename: Karim
authors.initials: K
authors.lastname: Bouhidel
authors.forename: Christophe
authors.initials: C
authors.lastname: Der
authors.forename: Nathalie
authors.initials: N
authors.lastname: Leborgne-Castel
authors.forename: Arti
authors.initials: A
authors.lastname: Mishra
authors.forename: Francis
authors.initials: F
authors.lastname: Marty
authors.forename: Benoît
authors.initials: B
authors.lastname: Schoefs
authors.forename: Iwona
authors.initials: I
authors.lastname: Adamska
authors.forename: Bengt L
authors.initials: BL
authors.lastname: Persson
authors.forename: Cornelia
authors.initials: C
authors.lastname: Spetea
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017920:Antiporters / Q000737:chemistry* / Q000502:physiology*; D017360:Arabidopsis / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000502:physiology*; D002417:Cattle; D002736:Chloroplasts / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D018384:Oxidative Stress; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D020524:Thylakoids / Q000378:metabolism*
chemical_list: D017920:Antiporters; D029681:Arabidopsis Proteins; D011994:Recombinant Proteins; C519172:TAAC protein, Arabidopsis; D049452:Green Fluorescent Proteins