Nucleotide transport proteins in environmental chlamydiae
Genomic analysis revealed that environmental chlamydiae use similar strategies to interact with their host cells as their pathogenic counterparts, the Chlamydiaceae (Horn et al., 2004). In collaboration with  I. Haferkamp and H. E. Neuhaus (University of Kaiserslautern, Germany) we are currently characterizing nucleotide transporters in environmental chlamydiae. In addition to an ATP/ADP translocase catalyzing the highly specific import of ATP in exchange for ADP, the environmental chlamydia UWE25 encodes four more genes encoding putative nucleotide transport proteins. Such unique transport proteins are commonly employed by plant plastids and have among the prokaryotes so far only been identified in Chlamydiae or the Rickettsiales (Winkler & Neuhaus, 1999). Comparative sequence analysis, heterologous gene expression, uptake studies and transcriptional analyses were performed in order to elucidate the role and function of these putative membrane carriers of UWE25. We could demonstrate that, like its pathogenic counterparts, UWE25 possesses a nucleotide triphosphate/H+ symporter. Furthermore, a third nucleotide transporter isoform was identified as the first known NAD+ transport protein among pro- and eukaryotes, importing NAD+ in its intact form in exchange for ADP (Haferkamp et al., 2004). All five nucleotide transporter genes were transcribed during intracellular growth of UWE25 in its amoeba host, and their concerted action allows for the import of energy, nucleotides, and electron carrier, representing a so far unknown adaptation of UWE25 to intracellular life. Since nucleotide transport proteins are unique to few obligate intracellular bacteria and plant plastids, these proteins could be well suited as target for the development of new antibiotics or herbicides.
Investigated by: Matthias Horn, Thomas Penz
This research is supported by: 
Links:
Environmental chlamydiae
Environmental chlamydia genomics and post-genomics
Environmental chlamydia genome database
ChlamydiaeDB
References:
- Haferkamp, I., Schmitz-Esser, S., Linka, N., Urbany, C., Collingro, A., Wagner, M., Horn, M., Neuhaus, H.E. (2004). A candidate NAD+ transporter in an intracellular bacterial symbiont related to chlamydiae. Nature 432, 622-625.
- Horn, M., Collingro, A., Schmitz-Esser, S., Beier, C.L., Purkhold, U., Fartmann, B., Brandt, P., Nyakatura, G.J., Droege, M., Frishman, D., Rattei, T., Mewes, H.-W., and Wagner, M. (2004). Illuminating the evolutionary history of chlamydiae. Science 304, 728-730.
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- Brinkman, F. S., Blanchard, J. L., Cherkasov, A. & other authors (2002). Evidence that plant-like genes in Chlamydia species reflect an ancestral relationship between Chlamydiaceae, cyanobacteria, and the chloroplast. Genome Res 12, 1159-1167.
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- Winkler, H. H. & Neuhaus, H. E.(1999). Non-mitochondrial ATP transport. Trends Biochem Sci 24, 64-68.
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