title: Characterization of an ATP translocase identified in the destructive plant pathogen "Candidatus Liberibacter asiaticus".
abstract: ATP/ADP translocases transport ATP across a lipid bilayer, which is normally impermeable to this molecule due to its size and charge. These transport proteins appear to be unique to mitochondria, plant plastids, and obligate intracellular bacteria. All bacterial ATP/ADP translocases characterized thus far have been found in endosymbionts of protozoa or pathogens of higher-order animals, including humans. A putative ATP/ADP translocase was uncovered during the genomic sequencing of the intracellular plant pathogen "Candidatus Liberibacter asiaticus," the causal agent of citrus huanglongbing. Bioinformatic analysis of the protein revealed 12 transmembrane helices and predicted an isoelectric point of 9.4, both of which are characteristic of this family of proteins. The "Ca. Liberibacter asiaticus" gene (nttA) encoding the translocase was subsequently expressed in Escherichia coli and shown to enable E. coli to import ATP directly into the cell. Competition assays with the heterologous E. coli system demonstrated that the translocase was highly specific for ATP and ADP but that other nucleotides, if present in high concentrations, could also be taken up and/or block the ability of the translocase to import ATP. In addition, a protein homologous to NttA was identified in "Ca. Liberibacter solanacearum," the bacterium associated with potato zebra chip disease. This is the first reported characterization of an ATP translocase from "Ca. Liberibacter asiaticus," indicating that some intracellular bacteria of plants also have the potential to import ATP directly from their environment.
authors: USDA-ARS-USHRL, 2001 South Rock Rd., Fort Pierce, FL 34945, USA.
authors: Cheryl M
authors: CM
authors: Vahling
authors: Yongping
authors: Y
authors: Duan
authors: Hong
authors: H
authors: Lin
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D019295:Computational Biology; D000226:Mitochondrial ADP, ATP Translocases / Q000235:genetics / Q000502:physiology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000382:microbiology*; D012230:Rhizobiaceae / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000226:Mitochondrial ADP, ATP Translocases