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Tapping the nucleotide pool of the host: novel nucleotide carrier proteins of Protochlamydia amoebophila
Author(s) -
Haferkamp Ilka,
SchmitzEsser Stephan,
Wagner Michael,
Neigel Nadjeschka,
Horn Matthias,
Neuhaus H. Ekkehard
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2006.05193.x
Subject(s) - biology , nucleotide , guanine nucleotide exchange factor , transporter , intracellular , transport protein , gtp' , biochemistry , gtpase , gene , intracellular parasite , amino acid , microbiology and biotechnology , genetics , enzyme
Summary 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, Pam NTT2, Pam NTT3 and Pam NTT5, 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. Pam NTT2 is a counter exchange transporter exhibiting submillimolar apparent affinities for all four RNA nucleotides, Pam NTT3 catalyses an unidirectional proton‐coupled transport confined to UTP, whereas Pam NTT5 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.