title: Functional characterization and organ distribution of three mitochondrial ATP-Mg/Pi carriers in Arabidopsis thaliana.
abstract: The Arabidopsis thaliana genome contains 58 membrane proteins belonging to the mitochondrial carrier family. Three members of this family, here named AtAPC1, AtAPC2, and AtAPC3, exhibit high structural similarities to the human mitochondrial ATP-Mg(2+)/phosphate carriers. Under normal physiological conditions the AtAPC1 gene was expressed at least five times more than the other two AtAPC genes in flower, leaf, stem, root and seedlings. However, in stress conditions the expression levels of AtAPC1 and AtAPC3 change. Direct transport assays with recombinant and reconstituted AtAPC1, AtAPC2 and AtAPC3 showed that they transport phosphate, AMP, ADP, ATP, adenosine 5'-phosphosulfate and, to a lesser extent, other nucleotides. AtAPC2 and AtAPC3 also had the ability to transport sulfate and thiosulfate. All three AtAPCs catalyzed a counter-exchange transport that was saturable and inhibited by pyridoxal-5'-phosphate. The transport activities of AtAPCs were also inhibited by the addition of EDTA or EGTA and stimulated by the addition of Ca(2+). Given that phosphate and sulfate can be recycled via their own specific carriers, these findings indicate that AtAPCs can catalyze net transfer of adenine nucleotides across the inner mitochondrial membrane in exchange for phosphate (or sulfate), and that this transport is regulated both at the transcriptional level and by Ca(2+).
authors.affiliation: Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125 Bari, Italy; Department of Sciences, University of Basilicata, Via Ateneo Lucano 10, 85100 Potenza, Italy.
authors.forename: Magnus
authors.initials: M
authors.lastname: Monné
authors.affiliation: Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125 Bari, Italy.
authors.forename: Daniela Valeria
authors.initials: DV
authors.lastname: Miniero
authors.affiliation: Department Willmitzer, Max-Planck-Institut fur Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Obata
authors.affiliation: Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125 Bari, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Daddabbo
authors.affiliation: Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125 Bari, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Palmieri
authors.affiliation: Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125 Bari, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Vozza
authors.affiliation: Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125 Bari, Italy.
authors.forename: M Cristina
authors.initials: MC
authors.lastname: Nicolardi
authors.affiliation: Department Willmitzer, Max-Planck-Institut fur Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany.
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.affiliation: Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125 Bari, Italy. Electronic address: ferdpalmieri@gmail.com.
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Palmieri
keywords: ATP–Mg/phosphate carrier; Arabidopsis; Membrane transport; Mitochondria; Mitochondrial carrier; Mitochondrial transporter