title: Tapping the nucleotide pool of the host: novel nucleotide carrier proteins of Protochlamydia amoebophila.
abstract: Protochlamydia amoebophila UWE25 is related to the Chlamydiaceae comprising major pathogens of humans, but thrives as obligate intracellular symbiont in the protozoan host Acanthamoeba sp. The genome of P. amoebophila encodes five paralogous carrier proteins belonging to the nucleotide transporter (NTT) family. Here we report on three P. amoebophila NTT isoforms, PamNTT2, PamNTT3 and PamNTT5, which possess several conserved amino acid residues known to be critical for nucleotide transport. We demonstrated that these carrier proteins are able to transport nucleotides, although substrate specificities and mode of transport differ in an unexpected manner and are unique among known NTTs. PamNTT2 is a counter exchange transporter exhibiting submillimolar apparent affinities for all four RNA nucleotides, PamNTT3 catalyses an unidirectional proton-coupled transport confined to UTP, whereas PamNTT5 mediates a proton-energized GTP and ATP import. All NTT genes of P. amoebophila are transcribed during intracellular multiplication in acanthamoebae. The biochemical characterization of all five NTT proteins from P. amoebophila in this and previous studies uncovered that these metabolically impaired bacteria are intimately connected with their host cell's metabolism in a surprisingly complex manner.
authors.affiliation: Pflanzenphysiologie, Technische Universität Kaiserslautern, Erwin Schrödinger Str., D-67653 Kaiserslautern, Germany.
authors.forename: Ilka
authors.initials: I
authors.lastname: Haferkamp
authors.forename: Stephan
authors.initials: S
authors.lastname: Schmitz-Esser
authors.forename: Michael
authors.initials: M
authors.lastname: Wagner
authors.forename: Nadjeschka
authors.initials: N
authors.lastname: Neigel
authors.forename: Matthias
authors.initials: M
authors.lastname: Horn
authors.forename: H Ekkehard
authors.initials: HE
authors.lastname: Neuhaus
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002689:Chlamydia / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial / Q000235:genetics; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D033704:Nucleotide Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009711:Nucleotides / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013379:Substrate Specificity; D014158:Transcription, Genetic; D014544:Uridine Triphosphate / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D033704:Nucleotide Transport Proteins; D009711:Nucleotides; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D014544:Uridine Triphosphate