Identification of the mitochondrial ATP-Mg/Pi transporter. Bacterial expression, reconstitution, functional characterization, and tissue distribution.

TitleIdentification of the mitochondrial ATP-Mg/Pi transporter. Bacterial expression, reconstitution, functional characterization, and tissue distribution.
Publication TypeJournal Article
Year of Publication2004
AuthorsFiermonte, G, De Leonardis, F, Todisco, S, Palmieri, L, Lasorsa, FMassimo, Palmieri, F
JournalJ Biol Chem
Volume279
Issue29
Pagination30722-30
Date Published2004 Jul 16
ISSN0021-9258
KeywordsAdenosine Triphosphate, Amino Acid Motifs, Antiporters, Calcium, Calcium-Binding Proteins, Catalysis, Cytoplasm, Diffusion, DNA, Complementary, Escherichia coli, Humans, Hydrogen-Ion Concentration, Kinetics, Liposomes, Magnesium, Membrane Transport Proteins, Mitochondria, Mitochondrial Proteins, Molecular Sequence Data, Phosphate Transport Proteins, Phosphates, Phospholipids, Plasmids, Potassium, Protein Isoforms, Protein Structure, Tertiary, Recombinant Proteins, Reverse Transcriptase Polymerase Chain Reaction, Sequence Homology, Amino Acid, Time Factors, Tissue Distribution
Abstract

The mitochondrial carriers are a family of transport proteins that, with a few exceptions, are found in the inner membranes of mitochondria. They shuttle metabolites, nucleotides, and cofactors through this membrane and thereby connect and/or regulate cytoplasm and matrix functions. ATP-Mg is transported in exchange for phosphate, but no protein has ever been associated with this activity. We have isolated three human cDNAs that encode proteins of 458, 468, and 489 amino acids with 66-75% similarity and with the characteristic features of the mitochondrial carrier family in their C-terminal domains and three EF-hand Ca(2+)-binding motifs in their N-terminal domains. These proteins have been overexpressed in Escherichia coli and reconstituted into phospholipid vesicles. Their transport properties and their targeting to mitochondria demonstrate that they are isoforms of the ATP-Mg/Pi carrier described in the past in whole mitochondria. The tissue specificity of the three isoforms shows that at least one isoform was present in all of the tissues investigated. Because phosphate recycles via the phosphate carrier in mitochondria, the three isoforms of the ATP-Mg/Pi carrier are most likely responsible for the net uptake or efflux of adenine nucleotides into or from the mitochondria and hence for the variation in the matrix adenine nucleotide content, which has been found to change in many physiopathological situations.

DOI10.1074/jbc.M400445200
Alternate JournalJ. Biol. Chem.
Citation Key10.1074/jbc.M400445200
PubMed ID15123600