title: Phylogenetic relationships of non-mitochondrial nucleotide transport proteins in bacteria and eukaryotes.
abstract: Current knowledge about the nucleotide metabolism of intracellular bacteria is very limited. Here we report on the identification of nucleotide transport proteins (NTT) of two obligate endoparasites, Caedibacter caryophila and Holospora obtusa, both alpha-proteobacteria, which reside in the vegetative macronucleus of Paramecium caudatum. For comparative studies, we also identified the first nucleotide transporter in chloroplasts of a red alga, i.e. Galdieria sulphuraria, and further homologs in plant chloroplasts. Heterologous expression of the NTT proteins from C. caryophila, H. obtusa, and G. sulphuraria in Escherichia coli demonstrate that the nucleotide influx mediated by these transporters is specific for ATP and ADP. The NTT proteins of C. caryophila and H. obtusa exhibit substantial sequence identity with their counterparts in chloroplasts and intracellular bacterial pathogens of humans, but not with the nucleotide transport system of mitochondria. Comprehensive phylogenetic analyses of bacterial and chloroplast NTT proteins showed that homologs in chloroplasts from plants, and green, red, stramenopile and glaucocystophyte algae are monophyletic. In contrast, the evolutionary relationships of the bacterial counterparts appear highly complex. In the presented phylogeny, NTT proteins of C. caryophila and H. obtusa are only distantly related to one another, although these two taxa are close relatives in 16S rRNA trees. The tree topology indicates that some bacterial NTT paralogs have arisen by gene duplications and others by horizontal transfer.
authors.affiliation: Universität Kaiserslautern, Pflanzenphysiologie, Postfach 3049, D-67653 Kaiserslautern, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Linka
authors.forename: Herbert
authors.initials: H
authors.lastname: Hurka
authors.forename: B Franz
authors.initials: BF
authors.lastname: Lang
authors.forename: Gertraud
authors.initials: G
authors.lastname: Burger
authors.forename: Herbert H
authors.initials: HH
authors.lastname: Winkler
authors.forename: Claudia
authors.initials: C
authors.lastname: Stamme
authors.forename: Claude
authors.initials: C
authors.lastname: Urbany
authors.forename: Inka
authors.initials: I
authors.lastname: Seil
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kusch
authors.forename: H Ekkehard
authors.initials: HE
authors.lastname: Neuhaus
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D020561:Alphaproteobacteria / Q000235:genetics*; D001692:Biological Transport; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005057:Eukaryotic Cells / Q000378:metabolism*; D008969:Molecular Sequence Data; D033704:Nucleotide Transport Proteins / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D000461:Rhodophyta / Q000235:genetics; D013045:Species Specificity
chemical_list: D033704:Nucleotide Transport Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate